DETECTION AND ESTIMATION OF THE VOLUME OF PNEUMOTHORAX USING REAL-TIME SONOGRAPHY - EFFICACY DETERMINED BY RECEIVER OPERATING CHARACTERISTIC ANALYSIS

OBJECTIVE. The purpose of this study was to determine the efficacy of real-time sonography for the detection and estimation of the volume of pneumothorax using receiver operating characteristic (ROC) analysis i n 27 patients evaluated by five radiologists using previously describe d sonographic findings, MATERIALS AND METHODS. Bilateral chest sonogra ms were obtained in 27 patients after we performed 26 needle biopsies of the lung and two transcostal biopsies of lesions at the dome of the liver, Thirteen unilateral pneumothoraces were found on radiographs d one at the time of the sonograms, The sonograms were recorded on video tape and later viewed by five blinded readers who scored each hemithor ax independently as to the likelihood and size of pneumothorax. From t hese interpretations we were able to calculate ROC curves and standard accuracy statistics for each observer and for pooled data, The result s were correlated with the findings on chest radiographs, which were u sed to verify the diagnoses. RESULTS. The area under the ROC curves ra nged from 0.63 to 0.79 in detecting any pneumothorax. The area under t he ROC curve derived by pooling readers and hemithoraces using the jac kknife method was 0.73. The average sensitivity of the five observers for pneumothorax was 73%, the specificity was 68%, and the negative an d positive predictive values were 89% and 40%, respectively. No signif icant correlation was found between readers' estimates of pneumothorax size made on the basis of sonographic findings and actual size as asc ertained from chest radiographs. CONCLUSION. Real time sonography is u seful to localize known pneumothorax but cannot be used to exclude the diagnosis. Moreover, sonography has a significant false-positive rate and is of no use in estimating the volume of a pneumothorax.