The use of adenosine deaminase as a diagnostic tool for peritoneal tuberculosis
Setting: Tygerberg Hospital, an academic hospital in the Western Cape, South Africa. Objective: To determine the diagnostic utility of ascitic fluid adenosine deaminase (ADA) in the diagnosis of tuberculous peritonitis. Design: A prospective study, carried out from February 1995 to February 1998, resulted in 178 paired ascites and serum specimens being collected from adult patients. Specimens were evaluated for biochemistry, ADA, microbiology and cytology; further investigations were done at the treating clinician's discretion. Diagnoses were made according the pre-determined criteria. Results: The median (range) ADA activity in the tuberculous group was 61.6 (17.5-115.0) U/L and was significantly higher than in any other diagnostic group (p < 0.05). Using ROC curves, a cut-off level of 30 U/L for the diagnosis of tuberculous peritonitis was found to yield the best results; corresponding sensitivity and specificity was 94% and 92%, respectively. No statistically significant difference in ADA activity was observed when tuberculous ascites occurred in the absence or presence of cirrhosis. Conclusions: Ascitic fluid ADA activity is useful in identifying those patients in whom the diagnosis of tuberculous peritonitis should be actively pursued to justify its routine use, at least in areas such as South Africa where TB is endemic. The presence or absence of underlying cirrhosis does not appear to distract from its diagnostic utility. © 2001 Harcourt Publishers Ltd.