[Pleural adenosine deaminase levels in tuberculous pleurisy--its diagnostic performance under the different prevalences in the different age of population].

In the diagnosis of pleural effusion, tuberculous pleurisy should always be considered because the prevalence of tuberculosis in Japan remains high. The measurement of adenosine deaminase (ADA) levels in pleural fluid is useful for the diagnosis of the tuberculous pleurisy because of its high sensitivity and specificity. However, no studies have addressed the post-test probability (= positive predictive value; PPV) of the test. Since the PPV depends on the pre-test probability (= prevalence) of the tuberculous pleurisy that varies with age, we have retrospectively evaluated the PPV in the different age population; the young (-35 years of age), the middle (36-65 years), and the old (66-years). A total of 208 data sets were collected; the tuberculosis (n = 52), malignancy (n = 34), non-specific infection (n = 31), transudates (n = 45), the others (n = 36), and unknown causes (n = 10). It was found that 1) the prevalence of tuberculous pleurisy was decreased with age, (70% in the young, 28.7% in the middle, and 8.5% in the old), 2) the PPV was the lowest in the old (53.8%), while the highest in the young (95.0%), and 3) no significant correlation was found between age and the ADA activity in pleural effusion.