Significance of pleural fluid cholesterol and beta-2 microglobulin levels for the differentiation of pleural effusions in childhood.

We studied 60 children, ages 3-15 years, with pleural effusions to determine the usefulness of different criteria for the separation of transudates from exudates. Twenty of these effusions were classified as transudates and 40 as exudates. Pleural cholesterol (P chol), pleural/serum cholesterol ratio (P/S chol), and pleural/serum beta 2 microglobulin (P/S beta 2 m) were determined to characterize pleural effusions and were compared with Light's criteria (pleural/serum protein ratio, pleural LDH, pleural/serum LDH ratio). With a threshold of 0.3, the sensitivity and specificity of P/S chol for diagnosis of exudates were 95 and 90%, respectively. With a threshold of 1.3, the sensitivity of P/S beta 2 m was 77.5%, and its specificity was 95%. Our findings indicate that determination of P chol and P/S chol, as well as Light's criteria, is of value for characterizing pleural effusions in childhood, but the measurement of P/S beta 2 m is less sensitive in distinguishing transudates from exudates and it should not be used routinely.