Chest ultrasonography versus supine chest radiography for diagnosis of pneumothorax in trauma patients in the emergency department.

BACKGROUND Chest X-ray (CXR) is a longstanding method for the diagnosis of pneumothorax but chest ultrasonography (CUS) may be a safer, more rapid, and more accurate modality in trauma patients at the bedside that does not expose the patient to ionizing radiation. This may lead to improved and expedited management of traumatic pneumothorax and improved patient safety and clinical outcomes. OBJECTIVES To compare the diagnostic accuracy of chest ultrasonography (CUS) by frontline non-radiologist physicians versus chest X-ray (CXR) for diagnosis of pneumothorax in trauma patients in the emergency department (ED). To investigate the effects of potential sources of heterogeneity such as type of CUS operator (frontline non-radiologist physicians), type of trauma (blunt vs penetrating), and type of US probe on test accuracy. SEARCH METHODS We conducted a comprehensive search of the following electronic databases from database inception to 10 April 2020: Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, MEDLINE, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL) Plus, Database of Abstracts of Reviews of Effects, Web of Science Core Collection and Clinicaltrials.gov. We handsearched reference lists of included articles and reviews retrieved via electronic searching; and we carried out forward citation searching of relevant articles in Google Scholar and looked at the "Related articles" on PubMed. SELECTION CRITERIA We included prospective, paired comparative accuracy studies comparing CUS performed by frontline non-radiologist physicians to supine CXR in trauma patients in the emergency department (ED) suspected of having pneumothorax, and with computed tomography (CT) of the chest or tube thoracostomy as the reference standard. DATA COLLECTION AND ANALYSIS Two review authors independently extracted data from each included study using a data extraction form. We included studies using patients as the unit of analysis in the main analysis and we included those using lung fields in the secondary analysis. We performed meta-analyses by using a bivariate model to estimate and compare summary sensitivities and specificities. MAIN RESULTS We included 13 studies of which nine (410 traumatic pneumothorax patients out of 1271 patients) used patients as the unit of analysis; we thus included them in the primary analysis. The remaining four studies used lung field as the unit of analysis and we included them in the secondary analysis. We judged all studies to be at high or unclear risk of bias in one or more domains, with most studies (11/13, 85%) being judged at high or unclear risk of bias in the patient selection domain. There was substantial heterogeneity in the sensitivity of supine CXR amongst the included studies. In the primary analysis, the summary sensitivity and specificity of CUS were 0.91 (95% confidence interval (CI) 0.85 to 0.94) and 0.99 (95% CI 0.97 to 1.00); and the summary sensitivity and specificity of supine CXR were 0.47 (95% CI 0.31 to 0.63) and 1.00 (95% CI 0.97 to 1.00). There was a significant difference in the sensitivity of CUS compared to CXR with an absolute difference in sensitivity of 0.44 (95% CI 0.27 to 0.61; P < 0.001). In contrast, CUS and CXR had similar specificities: comparing CUS to CXR, the absolute difference in specificity was -0.007 (95% CI -0.018 to 0.005, P = 0.35). The findings imply that in a hypothetical cohort of 100 patients if 30 patients have traumatic pneumothorax (i.e. prevalence of 30%), CUS would miss 3 (95% CI 2 to 4) cases (false negatives) and overdiagnose 1 (95% CI 0 to 2) of those without pneumothorax (false positives); while CXR would miss 16 (95% CI 11 to 21) cases with 0 (95% CI 0 to 2) overdiagnosis of those who do not have pneumothorax. AUTHORS' CONCLUSIONS The diagnostic accuracy of CUS performed by frontline non-radiologist physicians for the diagnosis of pneumothorax in ED trauma patients is superior to supine CXR, independent of the type of trauma, type of CUS operator, or type of CUS probe used. These findings suggest that CUS for the diagnosis of traumatic pneumothorax should be incorporated into trauma protocols and algorithms in future medical training programmes; and that CUS may beneficially change routine management of trauma.