Prediction of the diagnostic utility of thoracoscopy in pleural effusion

Malignancies are today becoming a more and more common cause of pleural effusions and thereby also a major indication for thoracoscopy. To facilitate the choice of the most suitable diagnostic procedure, a method of estimating the risk of malignancy is required. In order to present such a method, 334 patients with pleural effusions were examined. The predictive value for malignancy was determined for 7 variables, viz. the patient's sex, age, smoking habits, asbestos exposure, size of effusion, pleural fluid colour and eosinophils. The variables were evaluated both separately, combining two by two and by a logistic regression function. Malignant effusions were revealed in 47% of the patients. A bloody pleural fluid showed the strongest positive predictive value for malignancy, while greater than 30% eosinophils in the fluid had the strongest negative predictive value. The predictive value was further improved by combining pleural fluid colour and eosinophils. A logistic regression function using all 7 registered variables could discriminate correctly between malignant and non-malignant disease in 79% of all cases. Thus, patients at significant risk of having a malignant disease could be identified and referred for further examinations if needed. Thoracoscopy should be the method of choice for further examination of these patients as it reveals significant additional information beyond that achieved by cytology.