Diagnostic value of adenosine deaminase in nontuberculous lymphocytic pleural effusions

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Abstract
Adenosine deaminase (ADA) can aid in the diagnosis of tuberculous pleural effusions, but false-positive findings from lymphocytic effusions have been reported. The purpose of this study is to assess the ADA levels in nontuberculous lymphocytic pleural effusions (lymphocyte count >50%) of different aetiologies.Altogether, 410 nontuberculous lymphocytic pleural fluid samples were consecutively selected. These included malignant effusions (n=221), idiopathic effusions (n=76), parapneumonic effusions (n=35), postcoronary artery bypass graft surgery effusions (n=6), miscellaneous exudative effusions (n=21) and transudative effusions (n=51).The ADA level reached the diagnostic cut-off for tuberculosis (40 U·L−1) in seven of the 410 cases (1.71%). The negative predictive value of ADA for the diagnosis of pleural tuberculosis was 99% (403 of 407 cases) in the group of lymphocytic pleural effusions. In five of these seven patients ADA1and ADA2were measured, and in all these cases (100%) ADA1/ADApcorrectly classified these lymphocytic effusions as nontuberculous (ratio −1virtually excluded a diagnosis of tuberculosis in lymphocytic pleural effusions. Adenosine deaminase1/adenosine deaminasepcorrectly classified all nontuberculous lymphocytic pleural effusions with high adenosine deaminase levels.