Adenosine deaminase activity in pleuroperitonneal effusions, serum, peripheral blood mononuclear cells: an aid to differential diagnosis of tuberculous pleuroperitonitis from others
Abstract:
Adenosine deaminase (ADA) is the enzyme that catalyses the conversion of adenosine to inosine in purine metabolism. Its activity is high in mononuclear cells during the cellular immune response. Several studies use activity of the ezyme in various fluids as the diagnostic tool for differentiating tuberculosis from other diseases. We study the level of ADA activity in pleuroperitoneal fluids, serum and peripheral blood mononuclear cells (PBMC) in patients with pleuroperitoneal effusions. The ADA activity was assayed by enzymatic method. Of the 141 patients (31 tuberculosis, 110 other diseases including malignancy, cirrhosis, spontaneous bacterial peritonitis and parapneumonic effusion), the mean level of ADA activity in fluids, serum and PBMC were 39.3±17.3 µ/l, 29.6±10.9 µ/l and 4.9±3.6 µ/10⁶ wbc respectively in tuberculous patients and 23.6±14.5 µ/l, 27.5±12.9 µ/l, 3.3±3.2 µ/10⁶ wbc in other diseases. The ADA activity in pleuroperitoneal fluids and PBMC of tuberculosis was significantly higher than other diseases. The cut-off level of 31 u/l of ADA activity in pleuroperitoneal fluids had a sensitivity of 77.4%, specificity of 73.6%, PPV of 45.3%, NPV of 92% and accuracy of 74.5% in the diagnosis of tuberculosis. High pleuroperitoneal fluids ADA activity was also found in parapneumonic effusions, SLE, lymphoma and some metastatic carcinoma. This paper is the first report of ADA activity in PBMC in this group of patients. The cut-off level of 4.3 u/10⁶ wbc of ADA activity in PBMC had a sensitivity of 55.2%, specificity of 75%, PPV of 38.1%, NPV of 85.7% and accuracy of 70.7% in the diagnosis of tuberculosis. Although the level in tuberculosis was significantly higher than non-tuberculous group, but in comparision with malignancy group the level was not difference. In conclusion, ADA activity in pleuroperitoneal fluids, serum and PBMC has low diagnostic value in tuberculous pleuroperitonitis.