Screening of malignant pleural effusion by discriminant analysis

To assess the value of discriminant analysis as a method of optimizing the discriminant power of routine parameters in differentiating between malignant and non-malignant pleural effusions.

Retrospective review of the medical records of 245 patients with exudative pleural effusion.

The most powerful predictor of the malignant etiology of pleural effusion was a function that consisted of seven variables: age (years); effusion volume (coded as up to one third = 1, up to two thirds = 2, massive = 3); sedimentation rate (mm/h); monocyte count in the peripheral blood (cells/mm3); bloodstained exudate (coded as yes = 1, no = 2); and glucose (mg/dL) and iron (microg/dL) concentration in pleural fluid. This function showed a sensitivity of 77%, specificity of 85%, positive predictive value (PPV) of 76%, negative predictive value (NPV) of 86%, and was able to give an 82% rate of correct classification. In patients aged 50 years or younger, the NPV ranged between 91 and 98%, whereas in those older than 60 years, the PPV was 89%.

The calculated discriminant function is a simple, rapid, and inexpensive method for screening patients with pleural effusion for malignant etiology.