Cheung 2012.

Study characteristics
Patient sampling	Retrospective study
Patient characteristics and setting	Study location: Hong Kong, China Study period: January 2005 to December 2010 Care setting: emergency department (type of trauma centre not reported) Mass casualty: no Participants enrolled: 302 Participants included in analysis: 156: 103 men and 50 women Age: mean age 48.6 years (range 3 to 94 years) Type of injury: blunt abdominal trauma Injury severity: not reported Haemodynamic stability: stable and unstable conditions Inclusion criteria: all the blunt abdominal trauma patients identified in the hospital trauma registry and managed by the hospital trauma team in the emergency department Exclusion criteria: death at the emergency department after initial resuscitation; known ascites or peritoneal dialysis before the injury; blunt abdominal trauma patients who did not undergo FAST or standard confirmatory test; those with incomplete FAST findings
Index tests	Index test: FAST US protocol: FAST procedures followed the standard recommendation. Scanning was done on supine participants at 6 sites. Hardware used: ALOKASSD‐500 (probe model UST‐934N‐3.5, 3.5‐MHz convex sector probe) and GE Medical Logiq P5 Premium Ultrasound Console (probe model 4C 1.8‐4.0/D2.9MHz, curvilinear probe) Description of imaging technique: during the study period, there was no formal guideline in the hospital on how and when to perform the FAST. However, it was usual practice for FAST to be done by the emergency physicians or surgeons in charge of the trauma team in the emergency department, who had to be certified advanced trauma life support providers. 6 views were evaluated: the 4 quadrants of the abdomen and the suprapubic and subxiphoid region.
Target condition and reference standard(s)	Target condition: free fluid and air Reference standard: laparotomy, CT (technical specification was not reported), autopsy Description of technique: laparotomy started within 4 hours of admission was used as a gold standard confirmatory test for presence of intraperitoneal bleeding in blunt abdominal trauma participants for whom surgical exploration was clinically indicated. If the participant did not require laparotomy, abdominal CT scan was taken as the gold standard when the participant was still treated in the emergency department. Autopsy, in addition to CT scan if available, was used as surrogate standard test for participants who died during hospital stay without laparotomy performed.
Flow and timing	Time between US and reference standard: < 4 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?	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?	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
		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?	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