Diagnosis of Pneumothorax by Focused Assessment Sonography of Trauma(eFAST) and CT scan in Chest Trauma: Comparison of diagnostic accuracy

Abstract Aims and objectives: Pneumothorax is a common finding after trauma and with a wide range of clinical manifestations, from a concealed pneumothorax detectable only by a CT scan accidentally, to a potentially fatal tension pneumothorax. Pneumothorax can gradually progress to tension pneumothorax and become an emergency, consequently, a timely diagnosis is essential. Most traumatic patients have unstable conditions and are risky to transport for radiological evaluation, so they need a fast and bedside way of diagnosis. Currently, sonography is the only acceptable method which is available bedside. This study designed at this center to assess the diagnostic accuracy of ultrasound in trauma condition and comparing to that of CT scan as the final test for pneumothorax diagnosis. Method: After determining the sample size and the approval of the universitychr('39')s ethics committee, 290 patients were eligible for the study, matched the Advanced Trauma Life Support (ATLS). A computerized tomography scan (CT) and extended Focused Assessment Sonography of Trauma (eFAST) done for each patient. Sonography performed while regarding the standards for the eFAST examination. During the sonography examination, the process of resuscitation not impaired or stopped. Conform to the entry and exit criteria of the study, data collected in a questionnaire and entered in R software version 3.6.1. A series of tests including Sensitivity, specificity, positive and negative predictive values (PPV, NPV), positive and negative likelihood ratios (LR+, LR-), ROC curve analysis, McNemar test, and the Kappa coefficient used for evaluation. The results compared with that of the CT scan as the definitive diagnostic method. Results: from 290 patients enrolled in the study,  71% male and %29 were female. The mean age was 38.72 ± 16.7 years, and the age range was 14 to 78 years. The age distribution of the patients was not normal and skewed positively for 20 to 40 years old (median age 34.5 years old). The cause of trauma was non-penetrating in 99.3% and penetrating in 0.7%. According to the CT scan results as the final diagnostic method, 37 patients developed pneumothorax. Ultrasound sensitivity and specificity in pneumothorax diagnosis were 81.1% and 98.4%, respectively. The positive predictive and negative predictive for eFAST were 88.2% and 97.2%. Data fitness evaluated by the Kappa coefficient and McNemar test (Kappa of 0.82 and a p-value of 0.365). These tests showed a high concordance between the two diagnostic methods (eFAST and CT scan) for pneumothorax diagnosis. The area under the ROC curve for sonography was 0.898 and had a relatively good overlap with that of the ROC curve for CT scan. Conclusion: In general, extended Focused Assessment Sonography of Trauma is valuable in the diagnosis of pneumothorax with a diagnostic value close to CT scan. If positive for pneumothorax, the result is precise, but when negative, additional assessment required due to a lower sensitivity. It could also be a better substitute for a simple chest x-ray. Keyword: ultrasonography; sonography; trauma; CT scan; eFAST; pneumothorax