diagnostic efficacy of adenosine deaminase activity in patients with very low cd4 counts and pulmonary tuberculosis

Adenosine deaminase activity (ADA) is a commonly used marker for the diagnosis of pulmonary tuberculosis (PTB). There have been concerns about its usefulness in immune-compromised pa-tients, especially HIV positive patients with very low CD4 counts. The objective of this study was to evaluate the sensitivity of ADA in HIV sero-positive patients having low CD4 counts, and compare it with its sensitivity in HIV sero-negative patients. Suspected tubercular patients on the basis of clinical and radiolog-ical grounds were subjected to laboratory diagnosis for confirma-tion of pulmonary tuberculosis and HIV status after an informed consent. Each patient was evaluated for serum adenosine deami-nase activity (ADA) (by the sensitive colorimetric method de-scribed by Guisti), HIV (by Enzyme linked immune sorbent assay (ELISA) test), and CD4 counts. Out of a total 150 PTB patients, 120 were HIV sero-negative and 30 were HIV sero-positive. In HIV sero-positive PTB patients, the overall sensitivity, specificity, posi-tive predictive value and negative predictive value of ADA was 93%, 95%, 96%, and & 90% respectively, as compared to 95%, 95%, 99% and 76% in HIV in sero-negative PTB. The mean ADA value was 87.1+36.24 in HIV patient with CD4 count >200 cell/microL (mean CD4 count245 cell/microL), as compared to 71.32+36.35 in patients with CD4 count <200 cell/microL (mean CD4 count 86 cell/microL) which is statistically not significant (p-value > 0.05). There was no correlation between ADA activity and CD4 count (r = -0.460, p< 0.05). We concluded that ADA analysis is a sensitive marker for diagnosis of pulmonary tuberculosis even in HIV patients with very low CD4 counts especially in a high TB endemic region, like India.