Role of serum adenosine deaminase in pulmonary tuberculosis

Definitive laboratory diagnosis and confirmation of tuberculosis remains a major challenge because of lack of specificity and sensitivity of diagnostic methods especially in sputum smear negative tuberculosis. Many studies have proved the role of ADA in diagnosis of tuberculosis in effusion fluids and a decrease in ADA activity after treatment. This study was aimed to investigate the role of serum ADA level as an early diagnostic and prognostic marker for pulmonary tuberculosis (PTB).

This was a cohort study done on patients visiting the OPD Clinics of the department of Pulmonary Medicine at GMCH, Chandigarh. 50 sputum positive and 50 sputum negative tuberculosis patients and 100 controls were recruited. Serum ADA levels were measured at the start of treatment and again after two months of treatment. Its correlation with severity of disease was seen.

Mean serum ADA (IU/L) was found to be 35.293±30.941 in PTB patients and 11.819±8.023 in control groups and the difference was found to be highly significant (P<0.00). Mean ADA was 31.107±29.32 in sputum positive patients, 39.478±32.22 in sputum negative and 11.819±8.0235 in control groups. No statistically significant difference was observed amongst sputum positive and sputum negative patients. The levels decreased significantly after intensive phase of treatment. At the cut off values of 14.6IU/L, serum ADA had 78% sensitivity and 76% specificity (AUC=0.801, P value<0.00) to differentiate between PTB from healthy controls.

Serum ADA levels may be used as a biomarker for diagnosis of PTB and to evaluate the response to treatment at follow up.