PLEURAL FLUID VOLUME ESTIMATION - A CHEST RADIOGRAPH PREDICTION RULE

Rationale and Objectives. We devised a prediction rule for estimating pleural effusion volume on the basis of posteroanterior and lateral ch est radiographs.Methods. A prediction rule was devised for estimating pleural effusion volume on the basis of the presence or absence of a m eniscus on chest radiographs. The rule was tested and validated using separate data sets obtained from a retrospective review of patients ha ving both a chest radiograph and computed tomography (CT) scan (the go ld standard) within 24 hr of each other. The accuracy of the predictio n rule and the degree of interobserver agreement between tile two inde pendent readers were determined. Results. For the test and validation sets, the weighted accuracies of the prediction rule were 86% and 85%, respectively. The respective weighted interobserver agreements were 9 7% and 88%. Pleural effusions became visible as a meniscus on the late ral chest radiograph at a volume of approximately 50 ml; at a volume o f 200 ml, the meniscus could be identified on the posteroanterior radi ograph. At a volume of about 500 ml, the meniscus obscured the hemidia phragm. Conclusion. The volume of a pleural effusion can be estimated from the chest radiograph appearance with a reasonable degree of accur acy.