Adenosine deaminase activity - More than a diagnostic tool in tuberculous pericarditis
Aim: To improve the understanding of factors that influence adenosine deaminase (ADA) activity in large pericardial effusions. Methods: A prospective study was carried out at Tygerberg Academic Hospital, South Africa. Patients underwent echocardiographically guided pericardiocentesis. ADA activity, as well as biochemistry, haematology, cytology, and in some cases, histology, were determined. Human immunodeficiency virus (HIV) status was assessed in all patients. Results: Two hundred and thirty-three patients presented to Tygerberg Hospital with large pericardial effusions requiring pericardiocentesis. Tuberculous pericarditis accounted for 162 effusions (69.5%). An ADA cut-off level of 40 U/l resulted in a test sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic efficiency of 84.0%, 80.0%, 91.0%, 66.0% and 83.0%, respectively. Pericardial exudates with an ADA activity ≥ 40 U/l were associated with increased total leukocyte and neutrophil counts. Patients with tuberculous pericarditis and ADA > 40 U/l also had increased lymphocyte counts. Pericardial ADA activity < 30 U/l was associated with severe depletion of CD4 cell counts in HIV-positive patients. ADA levels were higher in cases with histological evidence of granulomatous inflammation than in cases with serofibrinous pericarditis. Conclusions: An ADA cut-off level of 40 U/l results in best diagnostic test results. ADA production appears to be influenced by factors associated with the antituberculous immune response.