Zhang 2006.

Study characteristics
Patient sampling	Prospective study
Patient characteristics and setting	Study location: China Study period: September 2004 to October 2005 Care setting: hospital emergency department Mass casualty: no Participants enrolled: 163 Participants included in analysis: 135: 114 men and 21 women Age: mean age 45 ± 15 years (range not reported) Type of injury: multiple trauma Injury severity: ISS 29.1 ± 12.4 Haemodynamic stability: stable and unstable conditions Inclusion criteria: patients with multiple trauma in either the resuscitation room or the emergency intensive care unit were enrolled. All patients suffered from blunt trauma, including traffic accident, falls, crush injuries, and other causes. Exclusion criteria: subcutaneous emphysema and/or cardiac arrest following probable tension pneumothorax
Index tests	Index test: EFAST, CXR US protocol: US was performed after initial rapid assessment by physical examination and essential resuscitation for participants in the resuscitation room. US was conducted in all participants admitted to the emergency intensive care unit and in hospitalised participants with impairment of lung function requiring a chest CT scan. Hardware used: SSD‐900, Aloka Co, Tokyo, Japan; 3.5‐MHz convex probe and occasionally a 7.5‐MHz linear probe Description of imaging technique: participants were kept in a supine position and an examination of the anterior, lateral, and posterior thoraces was performed. Bilateral US images were compared, and characteristic signs (i.e. pleural line, lung sliding, comet‐tail artefacts) were identified in either real‐time or time‐movement mode.
Target condition and reference standard(s)	Target condition: free fluid and air Reference standard: CT, 16‐slice spiral CT scanning unit (Volume Zoom, Siemens Co, Forchheim, Germany), CXR Description of technique: portable chest radiography and CT scans were performed before or after US with participants in the supine position. The results of chest CT and radiography were interpreted by independent radiologists who were unaware of participants' conditions and the findings of US.
Flow and timing	Time between US and reference standard: < 3 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?	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?	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