Domain	Signaling question	Signaling question	Risk of bias	Concerns about applicability
Domain 1: Patient selection
Patient selection	Was a consecutive or random sample of patients enrolled?	Did the study avoid inappropriate exclusions?	Could the selection of patients have introduced bias?	Is there concern that the included patients do not match the review question?
	Yes: if all consecutive or random samples of trauma patients were enrolled No: if convenience or selected samples of trauma patients were enrolled Unclear: if this was not clear from the report	Yes: if the study avoided inappropriate exclusions No: if patients were excluded inappropriately (e.g. age, gender, ethnicity) Unclear: if this was not clear from the report	Low: if "Yes" for all signalling questions High: if "No" was reported for at least 1 signalling question Unclear: if "Unclear" was reported for at least 1 signalling question	Low: if the included population consists of trauma patients in the emergency department setting, irrespective of age and gender, and if inappropriate exclusions were avoided High: if study authors used inappropriate exclusions Unclear: if insufficient information was available to make a judgement
Domain 2: Index tests
Index test ‐ CUS	Were CUS results interpreted without knowledge of the results of CT or tube thoracostomy?	Did the authors prespecify the criteria for a positive CUS finding?	Could the conduct or interpretation of the index test have introduced bias?	Is there concern that the index test, its conduct, or interpretation differ from the review question?
	Yes: if CUS results were interpreted without knowledge of the results of CT No: if CUS results were interpreted with knowledge of the results of CT Unclear: if this was not clear from the report	Yes: if criteria for positive CUS findings were prespecified No: if the criteria for positive CUS findings were not prespecified Unclear: if this was not clear from the report	Low: if "Yes" for all signalling questions High: if "No" was reported for at least 1 signalling question Unclear: if "Unclear" was reported for at least 1 signalling question	Low: if CUS was performed by frontline physicians (emergency physicians or trauma surgeons) in the emergency department High: if CUS was performed by someone other than emergency physicians or trauma surgeons outside of the emergency department setting Unclear: if insufficient information was available to make a judgement
Index test ‐ CXR	Were CXR results interpreted without knowledge of the results of CT or tube thoracostomy?		Could the conduct or interpretation of the index test have introduced bias?	Is there concern that the index test, its conduct, or its interpretation differ from the review question?
	Yes: if CXR results were interpreted without knowledge of the results of CT No: if CXR results were interpreted with knowledge of the results of CT Unclear: if this was not clear from the report		Low: if "Yes" for all signalling questions High: if "No" was reported for at least 1 signalling question Unclear: if "Unclear" was reported for at least 1 signalling question	Low: if CXR was performed in the supine fashion in the emergency department High: if CXR was not performed in the supine fashion or outside of the emergency department setting Unclear: if insufficient information was available to make a judgement
Domain 3: Reference standard
Reference standard ‐ CT or tube thoracostomy	Is the reference standard likely to correctly classify the target condition?	Were the reference standard results interpreted without knowledge of the results of the index tests?	Could the reference standard, its conduct, or its interpretation have introduced bias?	Is there concern that the target condition as defined by the reference standard does not match the review question?
	Yes: if an acceptable reference standard, such as CT or tube thoracostomy findings, was used No: if trauma patients did not undergo an acceptable reference standard Unclear: if this was not clear from the report	Yes: if CT results were interpreted without knowledge of results of the index tests (Note: Tube thoracostomy after CUS and CXR but before CT suggests clinical deterioration and was required for patient safety) No: if CT or tube thoracostomy results were interpreted with knowledge of results of the index tests Unclear: if this was not clear from the report	Low: if "Yes" for all signalling questions High: if "No" was reported for at least 1 signalling question. Unclear: if "Unclear" was reported for at least 1 signalling question	Low: if an acceptable reference standard, such as CT or tube thoracostomy findings, was used, and if CT results were interpreted without knowledge of the index tests High: if an acceptable reference standard was not used or if CT or tube thoracostomy results were interpreted with knowledge of results of the index tests Unclear: if insufficient information was available to make a judgement
Domain 4: Flow and timing
Flow and timing	Was there an appropriate interval between CUS, CXR, and CT/tube thoracostomy?	Did all patients receive a reference standard?	Were all patients included in the analysis?	Could patient flow have introduced bias?
	Yes: if CUS, CXR, and CT/tube thoracostomy was sequentially performed within 2 hours No: if CUS, CXR, and CT/tube thoracostomy was not sequentially performed within 2 hours Unclear: if this was not clear from the report	Yes: if all patients received a CT scan or tube thoracostomy No: if some patients did not receive a CT scan or tube thoracostomy Unclear: if this was not clear from the report	Yes: if all patients were included in the final analysis No: if all patients were not included in the final analysis Unclear: if this was not clear from the report	Low: if "Yes" for all signalling questions High: if "No" was reported for at least 1 signalling question Unclear: if "Unclear" was reported for at least 1 signalling question