Ascitic fluid adenosine deaminase insensitivity in detecting tuberculous peritonitis in the United States

Tuberculous peritonitis, although common in Third World countries, remains an uncommon cause of ascites in the United States. Ascitic fluid adenosine deaminase (ADA) activity has been proposed as a useful diagnostic test. The aim of this retrospective study was to determine the clinical utility of ascitic fluid ADA activity in diagnosing tuberculous peritonitis in a U.S. patient population. A total of 368 ascitic fluid specimens from a well‐characterized ascitic fluid bank, including tuberculous peritonitis (n = 7), tuberculous peritonitis in the setting of cirrhosis (n = 10), and consecutive specimens of widely varied etiologies (n = 351) were analyzed for ADA activity by ultraviolet spectrophotometry at 265 nm. The overall sensitivity of the ADA determination in diagnosing tuberculous peritonitis was only 58.8%, and the specificity was 95.4%. The accuracy of ADA determination (93.8%) compared favorably with that of the common ascitic fluid tests of white blood cell (WBC) count (>500/mm3), total protein (>2.5 g/dL), and combined WBC count and total protein (45.8%, 74.4%, and 81.3%, respectively). However, ADA was only 30% sensitive in detecting tuberculous peritonitis in the setting of cirrhosis, and cirrhosis was present in 59% of the tuberculous peritonitis patients in our population. In addition, malignancy‐related ascites (13%) and bacterial peritonitis specimens (5.8%) occasionally yielded false‐positive results. In conclusion, our results indicate that the ascitic fluid ADA activity has good accuracy but poor sensitivity and imperfect specificity in a U.S. patient population in which the prevalence of tuberculosis is low and underlying cirrhosis is common.