ISOENZYMES OF ADENOSINE-DEAMINASE IN PLEURAL EFFUSIONS - A DIAGNOSTIC-TOOL

SETTING: Tygerberg Hospital, an academic teaching hospital, Republic o f South Africa. OBJECTIVE: To identify the adenosine deaminase (ADA) i soenzymes as a diagnostic tool for tuberculosis in pleural effusions w ith increased ADA activity. DESIGN: Patients (n = 157) with exudative effusions and ADA activities >20 U/l, due to causes which satisfied pr edetermined diagnostic criteria, participated in the study. They consi sted of 87 tuberculous effusions, 27 infective effusions (12 empyemato us and 15 non-empyematous), 37 malignant effusions and six other exuda tive effusions (systemic lupus erythematosus, pancreatitis and lung em bolus). In each case the ADA isoenzymes in the pleural fluid were iden tified using polyacrylamide gel electrophoresis. In addition, microbio logy and cytology (including differential cell counts) were also carri ed out. RESULTS: Although ADA(1c) and ADA(2) were the predominant isoe nzymes observed in tuberculous effusions, while ADA(1c) and ADA(1m) we re predominant in infective non-empyematous effusions, no additional d iagnostic value was obtained. In the case of neoplastic effusions and other exudates, determination of ADA isoenzyme patterns also did not a ssist in diagnosing these conditions. CONCLUSION: Determination of pat terns of ADA isoenzymes does not enhance the overall diagnostic value of ADA activity in pleural effusions.