Validity of serum adenosine deaminase in diagnosis of tuberculosis

INTRODUCTION: Tuberculosis is one of the most important infectious causes of death worldwide. Ziehl-Neelsen staining of sputum has high specificity in tuberculosis endemic countries, but modest sensitivity which varies among laboratories. This study was set up to investigate the diagnostic value of serum Adenosine deaminase in diagnosis of tuberculosis. METHODS: In a cross sectional and prospective study Serums of 200 patients of positive sputum smear, negative sputum smear, extra-pulmonary tuberculosis and bacterial community acquired pneumonia collected from March 2011 to May 2012 were evaluated. The data were analyzed using SPSS software and P-value of <0.05 was considered significant. RESULTS: A total of 200 subjects were included in the study designed in four groups. In cut-off value of ≥24 U/l for ADA in smear positive patients defined the sensitivity, specificity and positive predictive value 12%, 98% and 86% respectively. In smear negative patients defined the 6%, 98% and 75%, and in extra-pulmonary tuberculosis patients defined the sensitivity 14%, 98% and 88% respectively. CONCLUSION: This study indicated that measurement of serum ADA level do not have enough sensitivity to assist in the diagnoses of tuberculosis patients from other respiratory diseases and not evaluated perform well enough to replace sputum smear microscopy. Thus, this tests have little role in the diagnosis of pulmonary tuberculosis.