ADA is an enzyme found in a variety tissues and blood cells including erythrocytes and lymphocytes. Its activity in body fluids is primarily related to the number, maturation and level of stimulation of lymphocytes (1). Although ADA has been used as a diagnostic test for tuberculous meningitis, pericarditis and pleural effusions, caution should be exercised when interpreting its activity in ascitic fluid, particularly in low endemic countries where cirrhosis may not be uncommon. In a study of patients with ascites in the U.S., the overall sensitivity of the ADA for TB peritonitis was 59 % with a specificity of 95% (1). Among cirrhotic patients, however, the sensitivity of ADA was only 30%! False-positive results are occasionally observed in bacterial peritonitis and malignancy-associated ascites (1). Parenthetically, the sensitivity of serum ascites-albumin gradient (SAAG) <1.1 for TB peritonitis is also low (50%) in the setting of chronic liver disease (2).
- Hillebrand DJ, Runyon BA, Yasmineh WG, Rynders GP. Ascitic fluid adenosine deaminase insensitivity in detecting tuberculous peritonitis in the United States. Hepatology 1996;24:1408-1412.
- Shakil AO, Korula J, Kanel GC, Murray NG, Reynolds TB. Diagnostic features of tuberculous peritonitis in the absence and presence of chronic liver disease: a case-control study. Am J Med 1996;100:179-185.