Use of adenosine deaminase (ADA) to diagnose suspected peritoneal tuberculosis in Rwanda: a cross-sectional study

Peritoneal tuberculosis is the most common cause of low albumin gradient ascites in developing countries, but it can be easily confused with other causes of ascites. Peritoneal tuberculosis requires early recognition of symptoms and signs in order to make a quick diagnosis for appropriate treatment. Measurement of adenosine deaminase (ADA) level > 39 in ascites fluid is an established test to diagnose peritoneal tuberculosis. Many low-income countries do not currently test for adenosine deaminase in ascites fluid, including Rwanda.

Cross-sectional, descriptive study conducted through the Internal Medicine Department of three university teaching hospitals in Rwanda. Participants were patients older than 16 years presenting to tertiary referral hospitals with ascites of unknown cause.

Of 103 ascites fluid samples collected, 52 of them (50.5%) had an elevated ADA, consistent with a presumptive diagnosis of peritoneal TB. Among those 52 subjects diagnosed with peritoneal TB, 39 out of 52 (75%) did not receive anti-TB medications. Among the 17 subjects who were treated with anti-TB medications, 4 of 17 (23.6%) did not have peritoneal TB based on ADA level. Samples with low-albumin gradient ascites were more likely to have high ADA ≥39 IU/L (p = 0.039).

Our findings suggest that 3out of 4 patients with PTB in Rwanda are not getting TB treatment and 1 in 4 patients who are taking TB medications do not need it. Even if the true number of Rwandans who are being undertreated and overtreated is less than our study suggests, these results should prompt a larger study of peritoneal tuberculosis. Adding adenosine deaminase (ADA) to the diagnostic tools available to clinicians could help achieve the goal of correctly putting every Rwandan with tuberculosis on treatment, while avoiding unnecessary tuberculosis medications in those who do not have the disease.