Diagnostic value of adenosine deaminase and glutamine in tuberculous pleural effusions

ABSTRACT

Two biochemiccal markers related to lymphocyte functions are adenosine deaminase [ADA] enzyme and glutamine [Glu.]. The discriminating value of both of these indices in differentiating tuberculous from other types of pleural effusions was studied. The present work included 23 patients with tuberculous pleural effusions, 14 patients with malignant effusions as well as 5 patients with post-pneumonic effusions. Pleural fluids and sera were obtained from each participant and used for determination of pleural and serum ADA activity as well as pleural glutamine. It was found that tuberculous pleural effusions had signficantly higher ADA than other types of effusions, while malignant effusions had significantly higher glutamine levels. When ADA activity of more than 30.2 U/L is considered, diagnostic tests of tuberculous effusions showed a sensitivity of 100%, specificity of 79%. A pleural fluid, serum ADA ratio above 2.1 was found in 100% of tuberculous and in 7% of carcinomatous effusions [sensitivity 100%, specificity 93%, diagnostic accuracy 97%]. All postpneumonic effusions had a ratio below 2.1 A pleural fluid glutamine level above 2.2 mg/dl, selected as the discriminating level, was found in 100% of malignant, 4% tuberculous and 20% of postpneumonic effusions. The combined assay of pleural ADA pleural/serum ADA and pleural glutamine provide in-formation in the deferential diagnosis of pleural effusions, especially differentiating tuberculous from malignant ones. These are easy, cheap and could be performed in any hospital lab, as a routine to help diagnosis of pleural effusions