Point‐of‐care ultrasonography for diagnosing thoracoabdominal injuries in patients with blunt trauma

Dirk Stengel; Johannes Leisterer; Paula Ferrada; Axel Ekkernkamp; Sven Mutze; Alexander Hoenning

doi:10.1002/14651858.CD012669.pub2

. 2018 Dec 12;2018(12):CD012669. doi: 10.1002/14651858.CD012669.pub2

Point‐of‐care ultrasonography for diagnosing thoracoabdominal injuries in patients with blunt trauma

Dirk Stengel ^1,^✉, Johannes Leisterer ², Paula Ferrada ³, Axel Ekkernkamp ⁴, Sven Mutze ⁵, Alexander Hoenning ¹

Editor: Cochrane Injuries Group

PMCID: PMC6517180 PMID: 30548249

Abstract

Background

Point‐of‐care sonography (POCS) has emerged as the screening modality of choice for suspected body trauma in many emergency departments worldwide. Its best known application is FAST (focused abdominal sonography for trauma). The technology is almost ubiquitously available, can be performed during resuscitation, and does not expose patients or staff to radiation. While many authors have stressed the high specificity of POCS, its sensitivity varied markedly across studies. This review aimed to compile the current best evidence about the diagnostic accuracy of POCS imaging protocols in the setting of blunt thoracoabdominal trauma.

Objectives

To determine the diagnostic accuracy of POCS for detecting and excluding free fluid, organ injuries, vascular lesions, and other injuries (e.g. pneumothorax) compared to a diagnostic reference standard (i.e. computed tomography (CT), magnetic resonance imaging (MRI), thoracoscopy or thoracotomy, laparoscopy or laparotomy, autopsy, or any combination of these) in patients with blunt trauma.

Search methods

We searched Ovid MEDLINE (1946 to July 2017) and Ovid Embase (1974 to July 2017), as well as PubMed (1947 to July 2017), employing a prospectively defined literature and data retrieval strategy. We also screened the Cochrane Library, Google Scholar, and BIOSIS for potentially relevant citations, and scanned the reference lists of full‐text papers for articles missed by the electronic search. We performed a top‐up search on 6 December 2018, and identified eight new studies which may be incorporated into the first update of this review.

Selection criteria

We assessed studies for eligibility using predefined inclusion and exclusion criteria. We included either prospective or retrospective diagnostic cohort studies that enrolled patients of any age and gender who sustained any type of blunt injury in a civilian scenario. Eligible studies had to provide sufficient information to construct a 2 x 2 table of diagnostic accuracy to allow for calculating sensitivity, specificity, and other indices of diagnostic test accuracy.

Data collection and analysis

Two review authors independently screened titles, abstracts, and full texts of reports using a prespecified data extraction form. Methodological quality of individual studies was rated by the QUADAS‐2 instrument (the revised and updated version of the original Quality Assessment of Diagnostic Accuracy Studies list of items). We calculated sensitivity and specificity with 95% confidence intervals (CI), tabulated the pairs of sensitivity and specificity with CI, and depicted these estimates by coupled forest plots using Review Manager 5 (RevMan 5). For pooling summary estimates of sensitivity and specificity, and investigating heterogeneity across studies, we fitted a bivariate model using Stata 14.0.

Main results

We included 34 studies with 8635 participants in this review. Summary estimates of sensitivity and specificity were 0.74 (95% CI 0.65 to 0.81) and 0.96 (95% CI 0.94 to 0.98). Pooled positive and negative likelihood ratios were estimated at 18.5 (95% CI 10.8 to 40.5) and 0.27 (95% CI 0.19 to 0.37), respectively. There was substantial heterogeneity across studies, and the reported accuracy of POCS strongly depended on the population and affected body area. In children, pooled sensitivity of POCS was 0.63 (95% CI 0.46 to 0.77), as compared to 0.78 (95% CI 0.69 to 0.84) in an adult or mixed population. Associated specificity in children was 0.91 (95% CI 0.81 to 0.96) and in an adult or mixed population 0.97 (95% CI 0.96 to 0.99). For abdominal trauma, POCS had a sensitivity of 0.68 (95% CI 0.59 to 0.75) and a specificity of 0.95 (95% CI 0.92 to 0.97). For chest injuries, sensitivity and specificity were calculated at 0.96 (95% CI 0.88 to 0.99) and 0.99 (95% CI 0.97 to 1.00). If we consider the results of all 34 included studies in a virtual population of 1000 patients, based on the observed median prevalence (pretest probability) of thoracoabdominal trauma of 28%, POCS would miss 73 patients with injuries and falsely suggest the presence of injuries in another 29 patients. Furthermore, in a virtual population of 1000 children, based on the observed median prevalence (pretest probability) of thoracoabdominal trauma of 31%, POCS would miss 118 children with injuries and falsely suggest the presence of injuries in another 62 children.

Authors' conclusions

In patients with suspected blunt thoracoabdominal trauma, positive POCS findings are helpful for guiding treatment decisions. However, with regard to abdominal trauma, a negative POCS exam does not rule out injuries and must be verified by a reference test such as CT. This is of particular importance in paediatric trauma, where the sensitivity of POCS is poor. Based on a small number of studies in a mixed population, POCS may have a higher sensitivity in chest injuries. This warrants larger, confirmatory trials to affirm the accuracy of POCS for diagnosing thoracic trauma.

Plain language summary

How accurate is bedside ultrasound for the diagnosis of injuries to the abdomen or chest in patients with blunt injuries?

Background and aims

People who sustain a road traffic crash or fall from a height are at risk for blunt body trauma (i.e. non‐penetrating trauma) and multiple injuries. Medical professionals caring for these patients in hospital need to know if vital organs or vessels are damaged, and whether there is any major bleeding that requires immediate intervention. Point‐of‐care sonography (POCS), a form of ultrasound, is a non‐invasive, radiation‐free, portable imaging technique that can be used at the patient's bedside. It is frequently used to help diagnose injuries in the emergency department. We reviewed the best scientific evidence about the accuracy of POCS, that is its ability to identify or exclude injuries correctly, compared to other diagnostic tests. We considered computed tomography, laparotomy, and autopsy to be good comparative tests against which to measure the accuracy of POCS.

Study characteristics

We searched for studies from the year in which the first paper about using ultrasound to diagnose trauma patients was published until 15 July 2017. We considered 2296 records and included 34 relevant studies that involved 8635 participants in this review. All 34 studies were published between 1992 and 2017, with the number of participants in each study ranging from 51 to 3181. Ten studies included only children, two studies only adults, and the remaining 22 studies included both children and adults.

Quality of the evidence

In many studies, important information about the selection of participants and choice of the diagnostic tests against which to compare POCS was not reported. We therefore rated the methodological quality of the available evidence mostly as unclear.

Key results

Point‐of‐care sonography had a sensitivity (i.e. the ability to detect a person with the disease) of 74% and a specificity (i.e. the ability to exclude a person without the disease) of 96%. Sensitivity and specificity varied considerably across studies, which was due in part to variation in study, participant, and injury characteristics. In children, both the sensitivity and specificity of POCS were lower than in an adult or mixed population, meaning that POCS was less able to identify or rule out an injury. Based on our results, we would expect that amongst 1000 patients of a mixed‐age population with suspected blunt trauma to the abdomen or chest, POCS would miss 73 patients with injuries, and would falsely suggest the presence of injuries in 29 patients who were unaffected. This result emphasises the need for additional imaging in trauma patients for whom POCS shows no injuries (i.e. a negative result), to check whether they are really injury‐free.

Summary of findings

Background

Target condition being diagnosed

Trauma, including multiple trauma (defined by an Injury Severity Score (ISS) ≥ 16, or, according to the new Berlin definition, by an Abbreviated Injury Scale (AIS) ≥ three for two or more different body regions and one or more additional variables from five physiologic parameters) (Pape 2014), remains a major cause of death and disability worldwide. Severe trauma mainly results from road traffic crashes and falls from a height. In 2010, according to data from the World Health Organization (WHO) Global Burden of Disease Project, motor vehicle crashes ranked eighth in the global death toll (Lozano 2012), and tenth in all sources of disability‐adjusted life years (Murray 2012). The WHO and United Nations Decade of Action for Road Safety campaign 2011 to 2020 was launched to raise awareness about this public health concern and to implement simple and effective primary prevention measures.

A 'treat first what kills first' strategy is now in place at most trauma centres across the world, fostered by standardised management algorithms such as Advanced Trauma Life Support (ATLS). Key steps of these algorithms are (Chapleau 2013):

maintain airways and establish sufficient oxygenation (i.e. by intubation and tube thoracostomy in case of pneumo‐ or haematothorax);
stop traumatic bleeding (e.g. by tourniquets on extremities, pelvic binders and external fixators, surgical or interventional control of haemorrhage, application of antifibrinolytics such as tranexamic acid, and transfusion of blood products, mainly coagulation factors).

Data from the German Trauma Registry suggest an overall mortality of 10% from severely injured patients managed within organised trauma networks and at high‐volume trauma centres (German Trauma Society 2014). There may be a biological threshold in trauma survivability that cannot be overcome by any of the treatment modalities currently available, and extra translational research efforts are needed to make a difference in future. Apart from unsurvivable brain and upper cervical spine injuries, the leading causes of early death in multiple trauma are chest injuries and abdominal and retroperitoneal haemorrhage (Pfeifer 2016). The presence of free fluid surrounding the liver or spleen, capsular tears, organ contusions or lacerations, and vascular lesions influences early decision making in major trauma.

Stabbing (by sharp tools or weapons such as knives) and shooting are associated with a high chance of organ or vessel injury. The distinct location of wounds may point towards significant trauma to the lungs, heart, mediastinum, liver, spleen, thoracic and/or abdominal aorta. The quality and quantity of injuries sustained in civilian settings and armed conflicts differ in many ways (e.g. by type of weapon, gun, or bullet, wound ballistics, protective armour, austere environment (i.e. where medical care is provided under less than optimal sanitary or hospital‐like conditions) and others). Most patients with penetrating trauma need immediate surgical exploration (specifically in case of haemodynamic instability), and preoperative imaging has a rather ancillary role in this situation.

In blunt trauma, however, radiographic imaging is an inevitable part of clinical work‐up. Physical examination may reveal indirect signs of internal injury (e.g. contusion marks), but these signs are inconsistent and neither sensitive nor specific. Computed tomography (CT) is regarded as the imaging standard in the emergency department and is currently also the undisputed diagnostic reference test in the trauma scenario. If patients are transferred immediately to the operating theatre before CT imaging, emergency laparotomy, laparoscopy, or thoracotomy is the reference standard of choice. If patients die in the emergency department before any imaging or surgical procedure can be undertaken, definitive diagnoses are obtained during pathological or forensic autopsy. Point‐of‐care sonography (POCS), however, can be performed during resuscitation, repeated wherever and whenever needed, and does not involve exposure to radiation.

Point‐of‐care sonography has emerged as an integral part of trauma algorithms and is the initial screening modality of choice for thoracoabdominal bleeding in most regions of the world. Like any other imaging procedure or diagnostic test used for screening purposes, it is important to verify that:

a negative index test result is reliable for excluding the condition of interest (guaranteeing that episodes of haemodynamic instability during decompressive brain surgery or fixation of spine, pelvic, or femoral fractures are not caused by sudden major abdominal, thoracic, or retroperitoneal bleeding);
a positive index test result is reliable for proving the condition of interest (thus minimising the number of negative or unnecessary thoracotomies and laparotomies, or their minimally invasive equivalents).

Both false‐negative and false‐positive findings of POCS may misguide trauma teams and affect care priorities adversely.

Diagnostic accuracy (or efficacy) is the first level of the Fryback‐Thornbury hierarchy of evaluating the utility of a diagnostic test procedure (Fryback 1991). While the value and utility of a certain test cannot be derived from its accuracy alone, it would be absurd to ask for the effectiveness or efficiency of an inaccurate diagnostic test.

Determining accuracy is thus the first indispensable step in health technology assessment of POCS. This review aimed to generate the best available evidence about the diagnostic accuracy of clinical ultrasound imaging protocols in the setting of thoracoabdominal and multiple trauma compared to appropriate reference standards. It will guide clinicians regarding the likelihood of chest and abdominal injuries given certain prior probabilities and ultrasound findings, and may facilitate the decision to perform a CT scan or to schedule patients for emergency laparoscopy or laparotomy, or other interventional procedures.

Given the (higher) potential utility and value of POCS in blunt compared to penetrating trauma, this review considered only original studies that included participants with blunt injuries or, in a mixed population, provided sufficient details to explore the accuracy of POCS in this group.

Another aspect that requires scrutiny is the use of POCS in paediatric trauma algorithms. Children are vulnerable to radiation for diagnostic purposes, and their lifetime‐attributable risk (LAR) of cancer due to medical imaging must be kept to the necessary minimum. Still, there may be situations in which acute and potentially life‐threatening conditions require radiation‐emitting (i.e. multi‐detector row computed tomography (MDCT)) rather than radiation‐free imaging techniques (e.g. POCS or magnetic resonance imaging (MRI)).

Index test(s)

Ultrasound has emerged as a standard for bedside imaging in emergency departments worldwide. Technological progress has led to increasingly lighter and mobile (i.e. handheld) equipment (also available in the preclinical setting, e.g. on helicopters or rescue vehicles). Further advancements include colour‐duplex, contrast‐enhanced imaging, and even three‐dimensional (3D) scanning.

In the trauma setting, POCS is typically performed as focused abdominal sonography for trauma (FAST) (Scalea 1999). In its basic form, FAST includes oblique views of the left upper, right upper, left lower, and right lower abdominal quadrants, as well as a sagittal scan of the mid‐abdomen and a transverse view of the pelvic region. The key target of the original FAST scan is free fluid as a surrogate of blood or active bleeding.

The genuine FAST protocol has been modified and supplemented in many ways. The most useful and technically simple extensions were to screen for haematothorax (using oblique or intercostal planes, or both) and, by a xiphoid view, for pericardial effusion. Point‐of‐care sonography has also proved to be reliable in detecting pneumothorax (Blaivas 2005). Skilled examiners may be able to show and grade abdominal organ injury, although this is likely to exceed the diagnostic limits of POCS in the early resuscitation phase.

In this review, we have used the term POCS rather than FAST because of the varying definitions and targets established in different centres and countries. In clinical practice, ultrasound (or ultrasonography) as an imaging technique is commonly abbreviated and understood as sonography. Altogether, the technological evolution of hardware, increasing skills of operators, and significant advancements in picture acquisition and processing have changed the view of healthcare providers about the role of ultrasonography in the critical care setting substantially. Ultrasound has evolved from a rough screening tool to a conclusive imaging modality.

The index test for this review was therefore any clinical POCS application performed in the setting of blunt trauma that is intended to detect direct or indirect signs of injuries of the thoracic, abdominal, or retroperitoneal cavity or space and/or its organs and vessels.

Clinical pathway

Clinical examination alone has little ‐ if any ‐ role in excluding injuries to the chest or abdomen. The presence of external injuries, such as seatbelt marks, may increase the likelihood of visceral tears, but their absence does not exclude important trauma. Currently, all major trauma algorithms incorporate thoracoabdominal POCS as a diagnostic imaging tool. However, the interpretation of ultrasound images depends on the experience and clinical background of individual operators. This subjective component influences decision making, and hampers comparisons between initial and follow‐up scans taken by different examiners. In 2013, Van Vugt and colleagues published an evidence‐based work‐up protocol for blunt trauma that illustrated the benefits of training trauma teams in POCS (FAST) in combination with an ATLS course (Van Vugt 2013).

Alternative test(s)

Currently, POCS is challenged by the liberal early use of MDCT, either as abdominal, thoracic, thoracoabdominal, or whole‐body MDCT. The latter has emerged as the diagnostic modality of choice in most European trauma centres, and is used in the USA and other high‐income nations as well. The so‐called 'pan‐scan' usually comprises a native cranial CT, followed by a contrast‐enhanced CT from the skull base to the pelvis and/or trochanteric region. Whole‐body MDCT is highly specific, thereby minimising false‐positive findings (Stengel 2012), and may thus influence care priorities according to the 'treat first what kills first' rule. Data from the German Trauma Registry suggest that the pan‐scan improves survival in both unselected trauma cohorts and haemodynamically unstable patients (Huber‐Wagner 2013). However, there are concerns regarding excess exposure to radiation caused by uncritical use of the pan‐scan at both the individual and population level (Asha 2012). While dose‐reducing reconstruction and processing algorithms are available, it is debatable whether they produce images that are similar in quality and diagnostic certainty to those produced by conventional protocols.

The pan‐scan is not only a competing imaging tool; it is also regarded as the diagnostic reference standard to which POCS findings must be compared. This leads to an interesting methodological conflict, as it will be almost impossible to compare both imaging modalities in a head‐to‐head fashion in the trauma scenario.

Rationale

In high‐income countries, it is doubtful whether POCS findings influence treatment decisions in severe trauma. This can be illustrated by the following four possible scenarios.

POCS is positive for free abdominal or thoracic fluid, or both, in a haemodynamically stable patient. This will prompt a CT scan (usually a pan‐scan) to identify bleeding sources. In most cases, haemostatic transfusion (plus transarterial embolisation (TAE)) and intensive care unit (ICU) monitoring will be the treatment of choice in this setting.
POCS is negative for free abdominal or thoracic fluid, or both, in a haemodynamically stable patient. This will prompt a CT scan (usually a pan‐scan) to verify that there are no active bleeding sources that were missed by ultrasound.
POCS is negative for free abdominal or thoracic fluid, or both, in a haemodynamically unstable patient. This will almost always prompt a CT scan (usually a pan‐scan) to identify bleeding sources and to decide about TAE or emergency surgery, or both.
POCS is positive for free abdominal or thoracic fluid, or both, in a haemodynamically unstable patient. Currently, it is unlikely that stability could not be achieved by haemostatic resuscitation and other critical care efforts to make patients pan‐scan ready.

Scenario 4 is relevant, but rare, in the Western world. There are very few occasions in which all resuscitation efforts fail and patients are scheduled for emergency thoracotomy or laparotomy, or both, based on POCS findings alone. Still, these situations occur, and clinical practice guidelines must include recommendations on how to cope with them.

In middle‐ and low‐income countries, however, POCS (in addition to conventional radiographs) may represent the most sophisticated or only non‐invasive diagnostic tool available to detect significant traumatic haemorrhage and guide triage. The Sichuan earthquake in 2008, which killed 69,197 people and left 18,222 missing, was a classic example. Focused abdominal sonography for trauma ultrasound proved to be effective, efficient, and possibly lifesaving under these exceptional circumstances (Zhou 2012). Similar observations were made after the earthquake in Haiti in 2010. The earthquake in Nepal in April 2015 (which killed more than 6000 and left 2.8 million people homeless) demonstrated how FAST can play a role in triaging patients effectively outside the context of clinical research.

Objectives

To determine the diagnostic accuracy of POCS for detection and exclusion of:

free fluid in the thoracic or abdominal cavities;
organ injuries with or without bleeding in the thoracic or abdominal cavities;
vascular lesions of the thoracic or abdominal aorta, or other major vessels; and
other injuries (e.g. pneumothorax);

compared to the following diagnostic reference standards: computed tomography (CT; 'pan‐scan'), magnetic resonance imaging (MRI), thoracotomy, laparotomy, laparoscopy, thoracoscopy, autopsy, or any combination of these.

Secondary objectives

The secondary objectives of this review were to investigate the influence of individual study and cohort characteristics such as the:

reference standard;
target condition;
patient age (paediatric versus non‐paediatric);
patient disease status: type of trauma, type of injury, haemodynamic stability, injury severity or probability of survival;
environment;
operator's expertise and background;
hardware;
test thresholds;

on both positive and negative POCS scans.

More details are provided in the Investigations of heterogeneity section of the review.

Methods

Criteria for considering studies for this review

Types of studies

We included:

either prospective or retrospective diagnostic cohort studies that enrolled patients with blunt trauma who:
1. underwent any type of POCS as primary imaging modality to screen for thoracoabdominal injuries; and
2. also underwent predefined imaging or invasive reference tests to verify POCS results;
studies that provided 2 x 2 tables (or sufficient information to tabulate results) to allow for calculating sensitivity, specificity, and other indices of diagnostic test accuracy.

We excluded:

diagnostic case‐control studies comparing patients with known case status to healthy controls, as this creates artificial populations and tends to overestimate sensitivity of the index test;
case series and case reports;
studies with unclear index or reference tests; and
studies that did not allow for creating 2 x 2 tables.

Participants

The target population of this review comprised people of any age or gender who sustained any type of blunt trauma in a civilian scenario and were transferred to a hospital of any care level. Also, in order to be eligible participants had to have undergone POCS as the primary imaging tool and to have been followed up either as inpatients or outpatients with different diagnostic modalities to verify whether the condition of interest was present or absent.

Because of clear differences in clinical management, we deliberately excluded people with penetrating injuries, as well as members of armed forces wounded in the battlefield.

Index tests

Any type of POCS performed in a trauma setting (e.g. FAST ultrasonography of the abdomen or thorax, or both, or any advanced ultrasound protocol) intended to detect:

free fluid (as a surrogate of bleeding) in the abdomen, retroperitoneal space, or chest;
injuries to solid organs such as the liver or spleen (including attempts to grade their severity);
lesions of major vessels; and
other injuries (e.g. pneumothorax, as indicated by air in the pleural space).

Variation in POCS technology and application (e.g. specification of ultrasound machines and probes and how up‐to‐date they were, and handling of inconclusive test results) is addressed in the Assessment of methodological quality section of the review. We planned to examine its potential influence on diagnostic accuracy estimates in the Investigations of heterogeneity section of the review.

Target conditions

This review focused on blunt thoracoabdominal and multiple trauma, meaning any blunt, non‐penetrating force to the abdomen and chest and both solid and hollow viscera, as well as both major vessels. Target conditions considered by this review included:

free fluid in the:
1. thoracic cavity (uni‐ or bilateral, where specified);
2. abdominal cavity (by abdominal quadrant, where specified);
3. retroperitoneal space;
4. pericardium; or
5. mediastinum;
organ injuries, defined as:
1. liver injuries (e.g. capsular tears, haematoma, tissue lacerations);
2. splenic injuries (e.g. capsular tears, haematoma, tissue lacerations);
3. injuries to other solid organs (e.g. pancreas, kidneys);
4. injuries to hollow viscera; or
5. any other organ laceration detected by ultrasonography;
vascular lesions, defined as:
1. dissection or rupture of the thoracic or abdominal aorta, or both;
2. rupture of other vessels such as the iliac arteries;
other injuries (e.g. pneumothorax, as indicated by air in the pleural space in the thoracic cavity).

We analysed the effect of different types of target conditions as part of our Investigations of heterogeneity. We categorised target conditions into surrogates of blunt trauma (i.e. free fluid and free air, named limited assessment), and both surrogates and direct signs of organ damage (i.e. organ injuries and vascular lesions, named complete assessment).

Reference standards

In order to be accepted as a diagnostic reference standard, the deliberate use (and the reasoning for its use) of the particular method needed to be specified. To avoid verification bias, all participants were required to undergo an independent imaging or invasive test, regardless of the initial POCS scan.

We classified the following tests as reference standards to confirm the presence or absence of the target condition:

any type of CT scan of the major body cavities (i.e. chest, abdomen, pelvis), either selective or performed as a whole‐body scan. We planned to stratify results for the use of intravenous or oral contrast agents, or both, and the time interval between POCS and CT;
any type of MRI of the major body cavities;
laparotomy (by a median or transverse approach), or laparoscopy, either diagnostic or therapeutic;
thoracotomy (by median sternotomy or a clamshell approach), or thoracoscopy, either diagnostic or therapeutic;
autopsy, either done by pathologists or forensic examiners.

Search methods for identification of studies

We developed a reproducible search strategy in major online databases based on recommendations of the Cochrane Diagnostic Test Accuracy (DTA) Group and a systematic review performed previously (Stengel 2005). We sought assistance and advice from the Cochrane Injuries Group and its Information Specialist to create a search algorithm with high sensitivity. We also requested access to the Cochrane Injuries Group Specialised Register and searched the Cochrane Library for relevant studies included in published reviews. Furthermore, we used a snowball procedure to identify related articles and articles cited in the reference lists of individual publications, and used Google Scholar as an additional search tool.

Electronic searches

We searched the following electronic sources.

Ovid MEDLINE (1946 to 15 July 2017).
PubMed (not MEDLINE) (1947 to 15 July 2017).
Ovid Embase (1974 to 15 July 2017).

Search strategies are shown in Appendix 1.

We performed a further search on 6 December 2018; details of the eight potentially relevant studies identified have been added to the Characteristics of studies awaiting classification and Studies awaiting classification sections, and may be incorporated into the review at the next update.

Searching other resources

A systematic review by Scherer and colleagues showed that results from studies that have not been published in a full‐text format are systematically different from fully published results (Scherer 2007). We therefore searched the BIOSIS database for conference abstracts to identify potentially relevant studies that had not yet been published in a journal format (see Appendix 1).

We planned to contact authors of individual studies by email, letter, or phone, if we considered their results to be important but needed further explanation or raw data. We guaranteed that any data exchange complied with the International Conference on Harmonisation Good Clinical Practice (ICH‐GCP) principles and rules and regulations of data safety and security.

Data collection and analysis

We employed standard operating procedures (SOP) for the selection of studies, data extraction, and recording. This included the following principles:

screening of titles, abstracts, and full texts of study reports identified by the search strategy by two review authors working independently;
use of a data extraction form (including individual study characteristics, individual patient profiles, definition of procedures, etc.);
dual assessment and data entry;
dual assessment of methodological quality of individual studies;
resolution of conflicts by a third review author.

This guarantees transparency and adherence to Cochrane standards and other recommendations (e.g. those issued by the EQUATOR (Enhancing the QUAlity and Transparency Of health Research) group).

Selection of studies

Two review authors (AH, JL) independently screened the titles and abstracts of the identified reports, documenting details of selected studies in a predefined electronic spreadsheet and assessing studies for eligibility in terms of the predefined inclusion and exclusion criteria. If it was not possible to make a decision based on title and abstract alone, the full texts of potentially relevant studies were assessed. Any disagreements between authors regarding the selection of studies were resolved by a third expert (DS). The study selection process is documented in a detailed flow chart (Figure 1).

Study flow diagram for the search conducted on 15 July 2017.

Data extraction and management

As stated above, we established an SOP for data extraction for systematic reviews, meta‐analyses, and health technology assessment (HTA) reports. We adhered to ICH‐GCP, Good Epidemiological Practice (GEP), and other relevant rules and recommendations. We have trained personnel on site to record, manage, and audit data, and our data storage modes comply with federal legislation on data safety for research purposes. Two review authors (AH, JL) independently extracted data from original papers in duplicate, and resolved discrepancies by discussion, moderated by a third review author (DS). They extracted the following information from published papers:

study characteristics (author, year of study, year of publication, journal reference, study design, inclusion/exclusion criteria, operator characteristics, hardware specifications, index test used, reference test used, general setting (urban/rural), mass casualty (yes/no));
patient characteristics (age, gender, type of trauma, type of injury, injury severity, haemodynamic stability, probability of survival);
outcome of the index test as assessed in the individual studies by diagnosing the target condition and, if available, the number of participants with inconclusive results or who had no test result;
diagnostic 2 x 2 tables, cross‐classifying the disease status on the basis of the reference test (i.e. number of true‐positive, false‐positive, false‐negative, and true‐negative results).

Diagnostic accuracy was expressed by individual and pooled indicators such as sensitivity and specificity with 95% confidence intervals (CI), positive and negative likelihood ratios (LR), positive predictive value (PPV), negative predictive value (NPV), and the summary receiver operating characteristic curve (SROC).

Assessment of methodological quality

Two review authors (AH, JL) independently used the QUADAS‐2 tool (the revised and updated version of the original Quality Assessment of Diagnostic Accuracy Studies list of items) to assess methodological quality of individual studies (Whiting 2011). Any discrepancies were resolved by discussion, moderated by a third review author (DS). QUADAS‐2 includes four main domains, namely: patient selection, index test, reference standard, and flow and timing. We assessed each domain with regard to risk of bias, rating them as 'low', 'high', or 'unclear'. We assessed concerns regarding applicability only for the first three domains, categorising them as 'low', 'high', or 'unclear'. Signalling questions were answered as 'yes', 'no', or 'unclear' (see also Appendix 2). By using tailored review‐specific signalling questions we were able to perform a custom‐made assessment of the methodological quality of all included studies. We omitted the signalling question "Was any case‐control design avoided?" in Domain 1: Patient selection since we did not include any case control study, case series, or case reports. We added three signalling questions to Domain 2: Index test and two signalling questions to Domain 3: Reference test referring to operator's expertise and background, technical features of the hardware, and appropriateness of the ultrasound protocol and reference imaging standard. In Domain 4: Flow and timing, we included the signalling question "Did all participants receive a reference standard?" in order to explore the risk of partial verification bias.

Statistical analysis and data synthesis

If at least one of the target conditions was detected (i.e. pneumothorax, free fluid, organ or vessel injury), we considered the patient (participant) to be traumatised or test‐positive. Otherwise, we considered the participant to be uninjured or test‐negative. Our observational unit of interest was thus the individual participant, not a particular injury, and we did not evaluate single target conditions separately in the primary analysis. We used inconclusive test results as reported in the primary studies. For individual studies, we calculated sensitivity and specificity with 95% CI, tabulated pairs of sensitivity and specificity with CI, and depicted estimates by coupled forest plots using Review Manager 5 (RevMan 5) (Review Manager 2014).

Due to the subjective nature of the interpretation of POCS findings, we expected implicit thresholds in test positivity. We assessed a possible threshold effect visually by plotting true‐positive rates (sensitivity) from each study against false‐positive rates (1 − specificity) in a receiver operating characteristic (ROC) space and coupled forest plots of sensitivity and specificity. Since the dichotomous operationalisation of the test result does not enable explicit thresholds, we used the bivariate model according to Reitsma 2005, which is a robust statistical model taking the underlying relationship between sensitivity and specificity into account. The random‐effects approach allows for calculating sensitivity and specificity estimates while controlling for heterogeneity across studies. We fitted the models in Stata (Stata 2017) using the 'metandi' command and produced SROC plots using RevMan 5. We estimated average sensitivities and specificities using the bivariate model. We obtained likelihood ratios post estimation using the parameters of the bivariate model (see Table 1).

1.

Population	Patients of any age and gender who sustained any type of blunt injury in a civilian scenario
Setting	Clinical evaluation at hospitals of any care level
Index test	Point‐of‐care sonography (POCS) as the primary imaging tool
Reference standard	Computed tomography (CT), magnetic resonance imaging (MRI), laparotomy, laparoscopy, thoracotomy, thoracoscopy, autopsy
Findings	POCS emerged as an integral part of trauma algorithms, and remains the point‐of‐care imaging tool of choice for screening for thoracoabdominal bleeding in most regions of the world. Determining the diagnostic accuracy of POCS in patients with blunt trauma may provide clinicians with valuable information on the likelihood of chest and abdominal injuries and may contribute to decision making regarding the performance of subsequent diagnostic tests.
Limitations	Methodological quality was hampered by severe under‐reporting in the included studies. We assessed risk of bias as unclear in more than half of the studies for the domains of patient selection and reference standard, and in one‐third of the studies for the index test. There was substantial heterogeneity among the results of the individual studies, which we investigated further by sources of heterogeneity (see Table 2).
No. of participants (studies)	Summary sensitivity (95% CI)	Summary specificity (95% CI)	Summary LR+ (95% CI)	Summary LR‐ (95% CI)	Positive predictive value (95% CI)	Negative predictive value (95% CI)	Consequences in a virtual cohort of 1000^a
							Missed injuries	Overtreated
8635 (34)	0.74 (0.65 to 0.81)	0.96 (0.94 to 0.98)	18.5 (10.8 to 40.5)	0.27 (0.19 to 0.37)	0.88 (0.81 to 0.94)	0.90 (0.87 to 0.93)	73 (If 280 people suffer an injury through trauma, 207 will be identified as injured, and 73 will be missed.)	29 (If 720 people do not suffer an injury through trauma, 29 will be treated as though they had been injured, i.e. overtreated.)
Sensitivity analysis with a children‐only cohort
1384 (10)	0.62 (0.47 to 0.75)	0.91 (0.81 to 0.96)	6.9 (2.5 to 18.8)	0.42 (0.26 to 0.65)	0.76 (0.53 to 0.89)	0.84 (0.77 to 0.90)	118 (If 310 children suffer an injury through trauma, 192 will be identified as injured, and 118 will be missed.)	62 (If 690 children do not suffer an injury through trauma, 62 will be treated as though they had been injured, i.e. overtreated.)
^aThe median prevalence was 28% for the complete study population and 31% for the children‐only cohort.

Investigation of heterogeneity	Number of studies	Summary sensitivity (95% CI)	Summary specificity (95% CI)	Chi^2a	P value^b
Reference standard
Single CT	25	0.75 (0.63 to 0.84)	0.97 (0.93 to 0.98)	0.18 (overall)	0.9160 (overall)
CT plus laparotomy	7	0.73 (0.58 to 0.84)	0.95 (0.87 to 0.98)	0.18 (overall)	0.9160 (overall)
Target condition
Limited to free fluid/free air	22	0.78 (0.68 to 0.85)	0.97 (0.96 to 0.99)	9.10 (overall) 0.06 (sensitivity) 8.08 (specificity)	0.0106 (overall) 0.8100 (sensitivity) 0.0045 (specificity)
Free fluid/free air and organ injuries/vascular lesions	7	0.80 (0.73 to 0.85)	0.88 (0.70 to 0.96)	9.10 (overall) 0.06 (sensitivity) 8.08 (specificity)	0.0106 (overall) 0.8100 (sensitivity) 0.0045 (specificity)
Age of participant
Children	10	0.63 (0.46 to 0.77)	0.91 (0.81 to 0.96)	7.32 (overall) 54.91 (sensitivity) 19.88 (specificity)	0.0258 (overall) 0.0000 (sensitivity) 0.0000 (specificity)
Adults/mixed	24	0.78 (0.69 to 0.84)	0.97 (0.96 to 0.99)	7.32 (overall) 54.91 (sensitivity) 19.88 (specificity)	0.0258 (overall) 0.0000 (sensitivity) 0.0000 (specificity)
Type of injury
Abdominal injury	27	0.68 (0.59 to 0.75)	0.95 (0.92 to 0.97)	17.36 (overall) 13.22 (sensitivity) 5.39 (specificity)	0.0002 (overall) 0.0003 (sensitivity) 0.0202 (specificity)
Thoracic injury	4	0.96 (0.88 to 0.99)	0.99 (0.97 to 1.00)	17.36 (overall) 13.22 (sensitivity) 5.39 (specificity)	0.0002 (overall) 0.0003 (sensitivity) 0.0202 (specificity)
^aLarge values of the Chi² statistic indicate that test performance may be associated with the particular covariate. ^bP values < 0.05 indicate statistical evidence that sensitivity and/or specificity differ between the examined groups.

Domain 1: Participant selection
Risk of bias	Q1. Was a consecutive or random sample of participants enrolled?	‒ 'Yes' if a consecutive or random sample of participants was enrolled ‒ 'No' if a non‐random (or non‐consecutive) selection method was used ‒ 'Unclear' if the procedures are only partially reported and you feel that both ’yes’ or ’no’ are inadequate
	Q2. Did the study avoid inappropriate exclusions (e.g. exclusion of patients with underlying diseases associated with intra‐abdominal fluid)	‐ 'Yes' if there were no inappropriate exclusions ‐ 'No' if there were inappropriate exclusions ‐ 'Unclear' if it is not clearly stated if there are any inappropriate exclusions
	Summary judgement of risk of bias	‒ Low risk: both answers are ’yes’ ‒ High risk: ≥ 1 answers are ’no’ ‒ Unclear risk: all other cases
Concerns regarding applicability	Q3. Are there concerns that the included patients and setting do not match the review question?	‒ 'Low' if all patients with blunt thoracoabdominal and/or multiple trauma are the unit of investigation, and if the population characteristics are representative of those who will receive the test in practice ‒ 'High' if patients with any type of acute abdomen are enrolled, or when there are other covariates that are reason for concern ‒ 'Unclear' if answering ’low’ or ’high’ is inappropriate
Domain 2: Index test
Risk of bias	Q1. Were the index test results interpreted without knowledge of the results of the reference standard?	‒ 'Yes' if there is a statement that the index test results were interpreted blind to the results of the reference test ‒ 'No' if this does not appear to be the case ‒ 'Unclear' if this information was not reported
	Q2. If a threshold (e.g. the quantity of free intra‐abdominal fluid, the number of areas with detectable fluid, etc.) was used, was it prespecified?	‐ 'Yes' if the threshold values were prespecified before the start of the study ‐ 'No' if the threshold values were selected on the basis of the collected data ‐ 'Unclear' if there is insufficient information to make a judgement
	Q3. Was the qualification of the ultrasound operator appropriate?	‒ 'Yes' if his/her background, training, and experience were sufficient according to clinical expert rating (e.g. the operator was a board‐certified/qualified trauma or emergency surgeon, radiologist, sonographer, etc.) ‒ 'No' if the qualification was rated as not appropriate by clinical experts ‒ 'Unclear' if this information was not reported
	Q4. Was the ultrasound hardware (i.e. generation, manufacturer, probe, etc.) up‐to‐date?	‒ 'Yes' if the technical features were up‐to‐date according to clinical expert rating (e.g. by mentioning the ultrasound hardware and probes (frequency) used) ‒ 'No' if the ultrasound hardware was rated as outdated ‒ 'Unclear' if this information was not reported
	Q5. Was the ultrasound protocol (i.e. 'classic' focused assessment with sonography in trauma (FAST)) appropriate?	‒ 'Yes' if the ultrasound protocol (e.g. screening for free fluid and/or air, organ lacerations, etc.) was appropriate according to clinical expert rating ‒ 'No' if this was not the case ‒ 'Unclear' if this information was not reported
	Summary judgement of risk of bias	‒ Low risk: ≥ 4 answers are ’yes’ ‒ High risk: ≥ 3 answers are ’no’ ‒ Unclear risk: all other cases
Concerns regarding applicability	Q6: Are there concerns that the definition or performance of the index test (i.e. point‐of‐care ultrasonography (POCS) for trauma) do not match generally accepted, established, or practiced rules or recommendations?	‒ 'Low concern' all patients with blunt thoracoabdominal and/or multiple trauma are screened with POCS in an established or recommended manner ‒ 'High concern' ultrasound protocols deviate significantly from established protocols; patients with any type of acute abdomen were enrolled; or other covariates were a reason for concern ‒ 'Unclear concern' if answering ’low’ or ’high’ is inappropriate
Domain 3: Reference test
Risk of bias	Q1. Is this the type of test that is likely to correctly classify the target condition?	‒ 'Yes' when computed tomography (CT) and/or magnetic resonance imaging (MRI), or any invasive procedure like laparotomy/laparoscopy, thoracotomy/thoracoscopy, or autopsy was used as a reference standard ‒ 'No' if no reference test was specified, or only positive POCS findings were confirmed by an imaging and/or invasive reference test ‒ 'Unclear' if answering ’yes’ or ’no’ is inappropriate
	Q2. Were the reference standard results interpreted without knowledge of the results of the index tests?	‒ 'Yes' if there is a statement that the reference standard results were interpreted blind to the results of the index test ‒ 'No' if this does not appear to be the case ‒ 'Unclear' if this information was not reported
	Q3. Was the qualification of doctors (i.e. radiologists, surgeons, etc.) determining the reference standard appropriate?	‒ 'Yes' if his/her background, training, and experience were sufficient according to clinical expert rating (e.g. the operator was a board‐certified/qualified trauma or emergency surgeon, radiologist, sonographer, etc.) ‒ 'No' if the qualification was rated as not appropriate by clinical experts ‒ 'Unclear' if this information was not reported
	Q4. Was the reference imaging standard (i.e. multidetector‐row computed tomography (MDCT) rows (4 to ≥ 256 slices), contrast imaging, etc.) up‐to‐date?	‒ 'Yes' if the technical features were up‐to‐date according to clinical expert rating (e.g. by mentioning the hardware and imaging protocols used) ‒ 'No' if the CT hardware or imaging protocols were rated as outdated ‒ 'Unclear' if this information was not reported
	Summary judgement of risk of bias	‒ Low risk: ≥ 3 answers are ’yes’ ‒ High risk: ≥ 2 answers are ’no’ ‒ Unclear risk: all other cases
Concerns regarding applicability	Q5: Are there concerns the definition or performance of the reference tests (e.g. CT, MRI, laparotomy, thoracotomy, autopsy, etc.) do not match generally accepted, established, or practiced rules or recommendations?	‒ 'Low concern' all patients with blunt thoracoabdominal or multiple trauma, or both undergo a thoracoabdominal or whole‐body CT scan irrespective of clinical or ultrasound findings ‒ 'High concern' reference tests are ordered selectively or conditional on clinical or ultrasound results ‒ 'Unclear concern' if answering ’low’ or ’high’ concern is inappropriate
Domain 4: Flow and timing
Risk of bias	Q1. Was there an appropriate interval between index test and reference standard?	‒ 'Yes' if the POCS scan was followed by any reference test within 30 minutes ‒ 'No' if the reference test was executed after 30 minutes, if the reference test was employed before POCS, or in case of any other conditions ‒ 'Unclear' if this information was not reported
	Q2. Did all participants receive a reference standard? (Risk of partial verification bias)	‒ 'Yes' if it is clear that all (or a random selection of) participants who received the index test also received the reference test ‒ 'No' if participants did or did not receive a reference test based on the outcome of the index test, or the selection of participants to receive the reference test was not random ‒ 'Unclear' if this information was not reported
	Q3. Did all participants receive the same (or any equivalent) reference standard?	‒ 'Yes' if all participants had the same (or an equivalent) reference standard ‒ 'No' if this was not the case ‒ 'Unclear' if this information was not reported
	Q4. Were all participants included in the analysis?	‒ 'Yes' if all participants entered into the study were included in the analysis ‒ 'No' if it appears that some of the participants were excluded from the analysis for whatever reason (e.g. did not complete the study, dubious test results) ‒ 'Unclear' if neither of the options above are appropriate
	Summary judgement of risk of bias	‐ Low risk: ≥ 3 answers are ’yes’ ‐ High risk: ≥ 2 answers are ’no’ ‐ Unclear risk: all other cases

Test	No. of studies	No. of participants
1 Main analysis set	34	8635
2 Sensitivity analysis set with lower sensitivity/specificity values in two original studies	34	8635

Study characteristics
Patient sampling	Retrospective study
Patient characteristics and setting	Study location: Miami, USA Study period: 2000 to 2005 Care setting: level 1 trauma centre Mass casualty: no Participants enrolled: 3181: 2274 men and 907 women Participants included in analysis: 3181 Age: mean age 39 ± 19 years Type of injury: abdominal trauma Injury severity: ISS 22.9 ± 18 Haemodynamic stability: stable conditions Inclusion criteria: blunt trauma patients who underwent both US as a part of initial assessment and CT scan of the abdomen. Patients were divided into 3 groups according to their ISS: Group 1: ISS 1 to 14; Group 2: ISS 16 to 24; Group 3: ISS ≥ 25 (group allocation is reported as in the published reports ‐ the trialists did not say what happened to patients who had an ISS = 15). Age, gender, mechanism of injury, physiologic parameters, laboratory test results, ISS, radiology reports, and all applied procedures were retrospectively reviewed by the study team. Exclusion criteria: penetrating trauma, no US examination or CT scan
Index tests	Index test: FAST US protocol: trauma team members performed US examinations on all blunt trauma participants in the resuscitation bay. The US was obtained with the participant in supine position by the attending, trauma fellow, or resident. A positive US examination was considered to be a true positive if the CT scan revealed free fluid, and considered to be a false positive if free fluid was not confirmed at the subsequent CT scan. Negative US findings were counted as true negatives if the CT scan was negative and the participant had an uneventful course, and considered to be a false negative if the participant had a negative US and positive CT examination or was operated on and felt to have a therapeutic laparotomy. Hardware used: Aloka SSD 1000 (Aloka Co Ltd, Wallingford, CT) with a 3.5‐MHz curved probe Description of imaging technique: 4 areas were examined: perihepatic, perisplenic, pelvic, and pericardial
Target condition and reference standard(s)	Target condition: free fluid Reference standard: CT (CT technique not specified), laparotomy Description of technique: not reported
Flow and timing	Time between US and reference standard: not reported
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Did the study avoid inappropriate exclusions?	Yes
		Unclear	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	Yes
Was the qualification of the US operator appropriate?	Unclear
Was the US hardware (i.e. generation, manufacturer, probe, etc.) up to date?	Yes
Was the US protocol (i.e. 'classic' FAST) appropriate?	Yes
Are there concerns that the definition or performance of the index test (i.e. POC US of trauma) do not match generally accepted, established, or practiced rules or recommendations?	No
		Low	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
Was the qualification of the doctors (i.e. radiologists, surgeons, etc.) determining the reference standard appropriate?	Unclear
Was the reference imaging standard (i.e. MDCT‐rows (4 to ≥ 256 slices), contrast‐imaging, etc.) up to date?	Yes
Are there concerns that the definition or performance of the reference tests (e.g. CT, MRI, laparatomy, thoracotomy, autopsy, etc.) do not match generally accepted, established, or practiced rules or recommendations?	Unclear
		Unclear	Unclear
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Unclear
Did all patients receive the same reference standard?	No
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard? (Risk of partial verification bias)	Yes
		Unclear

Study characteristics
Patient sampling	Prospective study
Patient characteristics and setting	Study location: Chicago, USA Study period: October 1996 to October 1997 Care setting: not reported Mass casualty: no Participants enrolled: 51: 35 boys and 16 girls Participants included in analysis: 51 Age: mean age 6 years 7 months (range 2 weeks to 16 years) Type of injury: abdominal trauma Injury severity: not reported Haemodynamic stability: stable conditions Inclusion criteria: children with blunt abdominal injuries examined with abdominal CT after initial surgical evaluation were examined with sonography. Only those children who did not require emergency surgery were invited to participate. Exclusion criteria: not reported
Index tests	Index test: US US protocol: abdominal sonography was performed after abdominal CT in all participants. The paediatric radiologist or sonographer performing the sonography was not aware of the clinical history, physical examination, or CT and laboratory results. Hardware used: 128XP10 or Sequoia (Acuson, Mountain View, CA) using a 2.5‐ to 8‐MHz transducer (Acuson), depending on the child’s size and physical build Description of imaging technique: US scan locations: longitudinal and transverse images of both upper quadrants of the abdomen and transverse views of the pancreas, bladder, and both lower quadrants to the abdomen to detect intraperitoneal and retroperitoneal fluid. A variable number of supplemental transverse and longitudinal images of the solid organs in the upper abdomen were subsequently obtained.
Target condition and reference standard(s)	Target condition: free fluid and organ injury Reference standard: abdominal and pelvis CT, helically on a HiSpeed Advantage CT scanner (General Electric Medical Systems, Milwaukee, WI) Description of technique: CT examination during dynamic bolus administration of IV contrast material with slice collimation ranging from 5 mm to 10 mm, depending on the size of the child
Flow and timing	Time between US and reference standard: < 24 hours
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
Did the study avoid inappropriate exclusions?	Yes
		Low	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	Yes
Was the qualification of the US operator appropriate?	Yes
Was the US hardware (i.e. generation, manufacturer, probe, etc.) up to date?	Yes
Was the US protocol (i.e. 'classic' FAST) appropriate?	No
Are there concerns that the definition or performance of the index test (i.e. POC US of trauma) do not match generally accepted, established, or practiced rules or recommendations?	No
		Low	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
Was the qualification of the doctors (i.e. radiologists, surgeons, etc.) determining the reference standard appropriate?	Yes
Was the reference imaging standard (i.e. MDCT‐rows (4 to ≥ 256 slices), contrast‐imaging, etc.) up to date?	Unclear
Are there concerns that the definition or performance of the reference tests (e.g. CT, MRI, laparatomy, thoracotomy, autopsy, etc.) do not match generally accepted, established, or practiced rules or recommendations?	No
		Low	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	No
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard? (Risk of partial verification bias)	Yes
		Low

Study characteristics
Patient sampling	Prospective, single‐blinded study
Patient characteristics and setting	Study location: Georgia, USA Study period: September 2003 to May 2004 Care setting: level 1 trauma centre Mass casualty: no Participants enrolled: 176: 100 men and 76 women Participants included in analysis: 176 Age: > 17 years Type of injury: abdominal and chest trauma Injury severity: not reported Haemodynamic stability: not reported Inclusion criteria: blunt trauma patients receiving a FAST examination followed by chest radiography and CT of the chest and/or abdomen and pelvis. Patients who had chest tube placement prior to CT scan were included in the analysis, and the presence of pneumothorax was considered to be verified if a rush of air was heard when the chest tube was inserted. Exclusion criteria: no completed examination for any reason
Index tests	Index test: FAST US protocol: 4 locations of each hemithorax (anterior second intercostal space at the midclavicular line, fourth intercostal space at the anterior axillary line, sixth intercostal space at the midaxillary line, and sixth intercostal space at the posterior axillary line) Hardware used: SonoSite 180PLUS (Bothell, WA) using a 4‐ to 2‐MHz microconvex broadband transducer Description of imaging technique: US images were obtained parallel to ribs at the rib interspaces. Depth settings were minimised to approximately 5 cm to optimise magnification of the superficial structures being imaged. Power Doppler was used to enhance the sonologist’s ability to identify pleural sliding whenever the sliding lung sign was not easily detected. Absence of the sliding lung sign at the midclavicular point anteriorly or at the fourth interspace at the anterior axillary line was considered indicative of a small pneumothorax; absence of the sliding lung sign at the midaxillary line, a medium pneumothorax; and absence of the sliding lung sign in the posterior axillary line, a large pneumothorax.
Target condition and reference standard(s)	Target condition: free fluid and air Reference standard: multigated CT scanner using 5‐mm thick slices and portable, supine anteroposterior chest radiographs (technique specification was not reported) Description of technique: all examinations (US, CT, radiography) were performed with the participant in the supine position
Flow and timing	Time between US and reference standard: not reported
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Did the study avoid inappropriate exclusions?	Yes
		Unclear	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	Yes
Was the qualification of the US operator appropriate?	Yes
Was the US hardware (i.e. generation, manufacturer, probe, etc.) up to date?	Yes
Was the US protocol (i.e. 'classic' FAST) appropriate?	Yes
Are there concerns that the definition or performance of the index test (i.e. POC US of trauma) do not match generally accepted, established, or practiced rules or recommendations?	No
		Low	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
Was the qualification of the doctors (i.e. radiologists, surgeons, etc.) determining the reference standard appropriate?	Yes
Was the reference imaging standard (i.e. MDCT‐rows (4 to ≥ 256 slices), contrast‐imaging, etc.) up to date?	Yes
Are there concerns that the definition or performance of the reference tests (e.g. CT, MRI, laparatomy, thoracotomy, autopsy, etc.) do not match generally accepted, established, or practiced rules or recommendations?	No
		Low	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard? (Risk of partial verification bias)	Yes
		Low

Study characteristics
Patient sampling	Multicentre prospective study
Patient characteristics and setting	Study location: USA Study period: July 2014 to July 2015 Care setting: 14 paediatric level 1 trauma centre Mass casualty: no Participants enrolled: 2188: gender not reported Participants included in analysis: 340 Age: 7.8 ± 4.6 years (2188 participants) Type of injury: abdominal trauma Injury severity: ISS 5 (IQR 1 to 10) Haemodynamic stability: stable and unstable conditions Inclusion criteria: children < 16 years of age were enrolled over a 1‐year period. The primary purpose of the data collection was to develop a clinical prediction model to determine which children were at very low risk for intra‐abdominal injury following blunt abdominal trauma and could safely avoid abdominal CT as a component of their initial evaluation. Exclusion criteria: presentation > 6 hours after injury, abdominal CT imaging prior to arrival at the paediatric trauma centre, isolated head or extremity mechanism of injury, same‐level falls, penetrating trauma, burns, and hanging injuries
Index tests	Index test: FAST US protocol: not reported Hardware used: not reported Description of imaging technique: not reported
Target condition and reference standard(s)	Target condition: free fluid and air Reference standard: CT (technique specification was not reported) or intraoperative findings, or both Description of technique: not reported
Flow and timing	Time between US and reference standard: not reported
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
Did the study avoid inappropriate exclusions?	Yes
		Unclear	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Unclear
If a threshold was used, was it pre‐specified?	Yes
Was the qualification of the US operator appropriate?	Unclear
Was the US hardware (i.e. generation, manufacturer, probe, etc.) up to date?	Unclear
Was the US protocol (i.e. 'classic' FAST) appropriate?	Unclear
Are there concerns that the definition or performance of the index test (i.e. POC US of trauma) do not match generally accepted, established, or practiced rules or recommendations?	Unclear
		Unclear	Unclear
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
Was the qualification of the doctors (i.e. radiologists, surgeons, etc.) determining the reference standard appropriate?	Unclear
Was the reference imaging standard (i.e. MDCT‐rows (4 to ≥ 256 slices), contrast‐imaging, etc.) up to date?	Unclear
Are there concerns that the definition or performance of the reference tests (e.g. CT, MRI, laparatomy, thoracotomy, autopsy, etc.) do not match generally accepted, established, or practiced rules or recommendations?	Unclear
		Unclear	Unclear
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	No
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard? (Risk of partial verification bias)	Yes
		Low

Study characteristics
Patient sampling	Cross‐sectional validation study
Patient characteristics and setting	Study location: Islamabad, Pakistan Study period: January 2010 to December 2011 Care setting: emergency department of a teaching hospital Mass casualty: no Participants enrolled: 100: 88% men and 12% women Participants included in analysis: 100 Age: mean age of 31.52 ± 16.79 years (range 2 to 71 years) Type of injury: blunt abdominal trauma Injury severity: not reported Haemodynamic stability: stable and unstable conditions Inclusion criteria: patients with a history of or mechanism of injury suggestive of blunt abdominal injury, any subjective complaints of abdominal or flank pain, presence of abdominal tenderness to palpation, presence of abdominal distension, external signs of injury such as abdominal wall bruising ('seat‐belt sign'), or elicitation of any peritoneal signs Exclusion criteria: patients with penetrating abdominal injuries
Index tests	Index test: FAST US protocol: FAST was performed as part of the primary or secondary survey of the participant in the emergency department. Using a portable US machine, the scans were performed and interpreted by a radiologist within 1 hour of the participant arriving at the hospital. All participants in the study underwent a FAST scan. Hardware used: live 2‐D mode (rapid B‐mode) and transducer frequencies between 3 and 6 MHz (no technique specification reported) Description of imaging technique: bedside US is an integral component of trauma management that is primarily used to detect free intraperitoneal fluid after blunt trauma. The trauma US examination focuses on dependent intraperitoneal sites where blood is most likely to accumulate: the hepatorenal space (i.e. Morison's pouch), the splenorenal recess, and the inferior portion of the intraperitoneal cavity (including pouch of Douglas).
Target condition and reference standard(s)	Target condition: free fluid and air Reference standard: CT (technique specification not reported), laparotomy (DPL) Description of technique: all participants underwent either CT or ELAP depending on their clinical condition. FAST examination results, which were recorded as positive or negative and were compared with the findings on CT or exploratory laparotomy, which were considered definitive. CT was recommended for the evaluation of haemodynamically stable participants. Haemodynamically unstable participants were evaluated further for other causes of haemorrhage by DPL and, if indications were fulfilled, underwent a laparotomy.
Flow and timing	Time between US and reference standard: not reported
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
Did the study avoid inappropriate exclusions?	Yes
		Unclear	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Unclear
If a threshold was used, was it pre‐specified?	Yes
Was the qualification of the US operator appropriate?	Yes
Was the US hardware (i.e. generation, manufacturer, probe, etc.) up to date?	Yes
Was the US protocol (i.e. 'classic' FAST) appropriate?	Yes
Are there concerns that the definition or performance of the index test (i.e. POC US of trauma) do not match generally accepted, established, or practiced rules or recommendations?	No
		Low	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
Was the qualification of the doctors (i.e. radiologists, surgeons, etc.) determining the reference standard appropriate?	Unclear
Was the reference imaging standard (i.e. MDCT‐rows (4 to ≥ 256 slices), contrast‐imaging, etc.) up to date?	Unclear
Are there concerns that the definition or performance of the reference tests (e.g. CT, MRI, laparatomy, thoracotomy, autopsy, etc.) do not match generally accepted, established, or practiced rules or recommendations?	Yes
		Unclear	High
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	No
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard? (Risk of partial verification bias)	Yes
		Low

Study characteristics
Patient sampling	Prospective cohort study
Patient characteristics and setting	Study location: USA Study period: July 1998 to June 1999 Care setting: level I trauma centre Mass casualty: no Participants enrolled: 164 Participants included in analysis: 152: 95 men and 57 women Age: mean age 34 (range 6 to 91 years) Type of injury: blunt abdominal trauma Injury severity: not reported Haemodynamic stability: not reported Inclusion criteria: a convenience sample of patients who presented to the emergency department following blunt abdominal trauma and who subsequently received CT scans of the chest or abdomen during their evaluations Exclusion criteria: transferred from another facility with known solid organ injury; if the CT was interrupted or not completed; if performing the secondary US would delay necessary patient care; or if the trauma was not a blunt mechanism
Index tests	Index test: FAST US protocol: US examinations were performed by emergency medicine residents or attending physicians experienced in the use of US for detecting haemoperitoneum. Ultrasonographers determined the presence or absence of liver or spleen injury prospectively. The specific purpose of the secondary US was to evaluate the liver and splenic parenchyma for solid organ injury. The secondary US consisted of long‐ and short‐axis scans through both organs. Hardware used: Toshiba SSH‐140A (Toshiba, San Francisco, CA) with a 3.75‐MHz phased array transducer Description of imaging technique: a 4‐view US examination to detect haemoperitoneum or pericardial effusion
Target condition and reference standard(s)	Target condition: free fluid and air Reference standard: CT (technique specification not reported) Description of technique: the criterion diagnostic standard was made using CT. All CT interpretations were performed by attending radiologists who were blinded to the results of the secondary US examination.
Flow and timing	Time between US and reference standard: not reported
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Did the study avoid inappropriate exclusions?	Yes
		Unclear	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Unclear
If a threshold was used, was it pre‐specified?	Yes
Was the qualification of the US operator appropriate?	No
Was the US hardware (i.e. generation, manufacturer, probe, etc.) up to date?	Yes
Was the US protocol (i.e. 'classic' FAST) appropriate?	Yes
Are there concerns that the definition or performance of the index test (i.e. POC US of trauma) do not match generally accepted, established, or practiced rules or recommendations?	No
		Unclear	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
Was the qualification of the doctors (i.e. radiologists, surgeons, etc.) determining the reference standard appropriate?	Yes
Was the reference imaging standard (i.e. MDCT‐rows (4 to ≥ 256 slices), contrast‐imaging, etc.) up to date?	Unclear
Are there concerns that the definition or performance of the reference tests (e.g. CT, MRI, laparatomy, thoracotomy, autopsy, etc.) do not match generally accepted, established, or practiced rules or recommendations?	No
		Low	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard? (Risk of partial verification bias)	Yes
		Low

Study characteristics
Patient sampling	Cross‐sectional study
Patient characteristics and setting	Study location: Iran Study period: not reported Care setting: hospital emergency department Mass casualty: no Participants enrolled: 200: 133 men and 67 women Participants included in analysis: 200 Age: mean age 29.6 ± 18.3 years (range not reported) Type of injury: blunt abdominal trauma Injury severity: GCS 12.9 ± 3.4 Haemodynamic stability: stable conditions Inclusion criteria: haemodynamically stable patients with severe blunt trauma referred to the emergency department of Shahid Beheshti hospital in Kashan, Iran. Severe trauma was assumed if the mechanism of trauma was high energy (falls more than 3 m, motor vehicle accident with a speed more than 50 km/h, crush injuries, rollover, and pedestrian accidents), or if severe injuries such as vertebral or pelvic fractures were detected. Exclusion criteria: haemodynamically unstable patients (systolic blood pressure < 90 mmHg), penetrating trauma, pregnant women, and those with underlying diseases associated with intra‐abdominal fluid (cirrhosis, congestive heart failure)
Index tests	Index test: FAST US protocol: evaluation by FAST in the supine position Hardware used: Medison ultrasound (V20) curvilinear 3.5‐ to 5‐microhertz transducer Description of imaging technique: the Huang classification was used for measurement of the intra‐abdominal fluid. 1 point was given for each intra‐abdominal region (Douglas pouch, hepatorenal recess, perisplenic and paracolic gutters) if free intra‐abdominal fluid was present; 2 points were given if > 2 mL free fluid was seen in the hepatorenal recess and Douglas pouch, or floating bowel loops were observed.
Target condition and reference standard(s)	Target condition: free fluid and air Reference standard: CECT, Toshiba‐Astion (no further specification of technique reported) Description of technique: US followed by abdominopelvic CT for all participants from the diaphragm dome to pubis symphysis with IV contrast (Visipaque 270 mg vial, 1 mL/kg). The CT scan was reported by a second radiologist who was blinded to the results of the US.
Flow and timing	Time between US and reference standard: not reported
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Did the study avoid inappropriate exclusions?	No
		High	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	Yes
Was the qualification of the US operator appropriate?	Yes
Was the US hardware (i.e. generation, manufacturer, probe, etc.) up to date?	Yes
Was the US protocol (i.e. 'classic' FAST) appropriate?	Yes
Are there concerns that the definition or performance of the index test (i.e. POC US of trauma) do not match generally accepted, established, or practiced rules or recommendations?	No
		Low	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
Was the qualification of the doctors (i.e. radiologists, surgeons, etc.) determining the reference standard appropriate?	Unclear
Was the reference imaging standard (i.e. MDCT‐rows (4 to ≥ 256 slices), contrast‐imaging, etc.) up to date?	Yes
Are there concerns that the definition or performance of the reference tests (e.g. CT, MRI, laparatomy, thoracotomy, autopsy, etc.) do not match generally accepted, established, or practiced rules or recommendations?	No
		Low	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard? (Risk of partial verification bias)	Yes
		Low

Study	Reason for exclusion
Abdulrahman 2015	Insufficient information to calculate diagnostic accuracy
Ala 2016	Inadequate reference standard
Arrillaga 1999	Inadequate reference standard
Beck‐Razi 2007	Penetrating trauma
Behboodi 2016	Inadequate diagnostic values
Brooks 2004a	Penetrating trauma
Brooks 2004b	Inadequate reference standard
Brown 2001	Inadequate reference standard
Byars 2013	Inadequate index test
Cook 2015	Insufficient information to calculate diagnostic accuracy
Coskun 2011	Inadequate reference standard
Dan 2010	Inadequate reference standard
Deunk 2010	Inadequate index test
Donmez 2011	Insufficient information to calculate diagnostic accuracy
Faruque 2013	Inadequate reference standard
Hamada 2016	Insufficient information to calculate diagnostic accuracy
Helling 2007	Insufficient information to calculate diagnostic accuracy
Heyn 2008	Inadequate reference standard
Holmes 2012	Penetrating trauma
Hyacinthe 2012	Penetrating trauma
Ianniello 2014	Insufficient information to calculate diagnostic accuracy
Ingeman 1996	Insufficient information to calculate diagnostic accuracy
Jalli 2009	Inadequate index test
Kaya 2015	Inadequate reference standard
Kern 1997	Penetrating trauma
Kirkpatrick 2002	Inadequate reference standard
Kirkpatrick 2004	Insufficient information to calculate diagnostic accuracy
Kirkpatrick 2005	Inadequate reference standard
Krupnick 1997	Case‐control study
Ku 2013	Penetrating trauma
Kumar 2014	Insufficient information to calculate diagnostic accuracy
Lichtenstein 2005	Insufficient information to calculate diagnostic accuracy
Matsumoto 2016	Insufficient information to calculate diagnostic accuracy
Mihalik 2012	Insufficient information to calculate diagnostic accuracy
Moylan 2007	Inadequate reference standard
Mumtaz 2016	Penetrating trauma
Nagarsheth 2011	Penetrating trauma
Natarajan 2010	Insufficient information to calculate diagnostic accuracy
Pak‐art 2003	Inadequate reference standard
Richards 2004	Inadequate reference standard

Study characteristics
Patient sampling	Retrospective cross‐sectional study
Patient characteristics and setting	Study location: Singapore, Asia Study period: January 2009 to December 2010 Care setting: emergency department of a tertiary hospital Mass casualty: no Participants enrolled: 476: 389 men and 87 women Participants included in analysis: 221 Age: mean age 38.9 years (range not reported) Type of injury: blunt abdominal trauma Injury severity: not reported Haemodynamic stability: not reported Inclusion criteria: the identities of trauma patients who presented to the emergency department resuscitation room were acquired from the file and verified with the hospital's trauma registry. The performance of US was a mandated field in the trauma registry. Exclusion criteria: penetrating trauma and burns
Index tests	Index test: FAST US protocol: FAST, no further details reported Hardware used: not reported Description of imaging technique: not reported
Target condition and reference standard(s)	Target condition: free fluid and air, organ injury Reference standard: CT, no further details reported Description of technique: not reported
Flow and timing	Time between US and reference standard: not reported
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Did the study avoid inappropriate exclusions?	Yes
		Unclear	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Unclear
If a threshold was used, was it pre‐specified?	Yes
Was the qualification of the US operator appropriate?	No
Was the US hardware (i.e. generation, manufacturer, probe, etc.) up to date?	Unclear
Was the US protocol (i.e. 'classic' FAST) appropriate?	Unclear
Are there concerns that the definition or performance of the index test (i.e. POC US of trauma) do not match generally accepted, established, or practiced rules or recommendations?	Unclear
		Unclear	Unclear
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
Was the qualification of the doctors (i.e. radiologists, surgeons, etc.) determining the reference standard appropriate?	Unclear
Was the reference imaging standard (i.e. MDCT‐rows (4 to ≥ 256 slices), contrast‐imaging, etc.) up to date?	Unclear
Are there concerns that the definition or performance of the reference tests (e.g. CT, MRI, laparatomy, thoracotomy, autopsy, etc.) do not match generally accepted, established, or practiced rules or recommendations?	No
		Unclear	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Did all participants receive a reference standard? (Risk of partial verification bias)	Yes
		Low

Study characteristics
Patient sampling	Prospective cross‐sectional study
Patient characteristics and setting	Type of injury: polytraumatised patients with a blunt mechanism Participants included in analysis: 150 Age: mean age 27.98 ± 20.39 years Haemodynamic stability: unstable
Index tests	Index test: FAST US
Target condition and reference standard(s)	Reference standard: exploratory laparotomy
Flow and timing
Comparative
Notes	May be incorporated into the review at the next update

PERMALINK

Point‐of‐care ultrasonography for diagnosing thoracoabdominal injuries in patients with blunt trauma

Dirk Stengel

Johannes Leisterer

Paula Ferrada

Axel Ekkernkamp

Sven Mutze

Alexander Hoenning

Abstract

Background

Objectives

Search methods

Selection criteria

Data collection and analysis

Main results

Authors' conclusions

Plain language summary

Summary of findings

Background

Target condition being diagnosed

Index test(s)

Clinical pathway

Alternative test(s)

Rationale

Objectives

Secondary objectives

Methods

Criteria for considering studies for this review

Types of studies

Participants

Index tests

Target conditions

Reference standards

Search methods for identification of studies

Electronic searches

Searching other resources

Data collection and analysis

Selection of studies

1.

Data extraction and management

Assessment of methodological quality

Statistical analysis and data synthesis

1.

Investigations of heterogeneity

Summary of findings 2. Investigation of heterogeneity.

Sensitivity analyses

Assessment of reporting bias

Results

Results of the search

Included studies

Excluded studies

Methodological quality of included studies

2.

3.

Patient selection

Index test

Reference standard

Flow and timing

Findings

Diagnostic performance of individual studies comparing POCS with reference standard

4.

Estimates derived from the bivariate model comparing POCS with reference standard

5.

Heterogeneity

a. Effect of reference standard

b. Effect of target condition

6.

7.

c. Effect of participant age

8.

d. Effect of type of injury

9.

Sensitivity analysis

a. Effect of study quality

b. Effect of two independent reviewers within original studies

c. Effect of patient age

Discussion

Summary of main results

Strengths and weaknesses of the review

Applicability of findings to the review question