Cerebrospinal fluid adenosine deaminase for the diagnosis of tuberculous meningitis.

ABSTRACT

Background: A consensus on the diagnostic utility of cerebrospinal fluid adenosine deaminase (ADA) for tuberculous meningitis (TBM) is lacking. Methods: Patients aged ≥12 years admitted with CNS infections were enrolled prospectively. ADA was measured with spectrophotometry. Results: We enrolled 251 TBM and 131 other CNS infections. The optimal cutoff of ADA was calculated at 5.5 U/l against microbiological reference standard with area under curve 0.743, sensitivity 80.7%, specificity 60.3%, positive likelihood ratio 2.03 and negative likelihood ratio 3.12. The widely used cutoff value 10 U/l had specificity 82% and sensitivity 50%. The discriminating power was higher for TBM versus viral meningoencephalitis than bacterial or cryptococcal meningitis. Conclusion: Cerebrospinal fluid ADA has a low-to-modest diagnostic utility.

The diagnosis of tuberculosis (TB) of the brain is mainly made by testing cerebrospinal fluid, a clear liquid that flows in and around the brain and spinal cord. Adenosine deaminase (ADA) is a protein whose production and activity are increased in many diseases, such as TB. ADA testing in cerebrospinal fluid is widely used for the diagnosis of brain TB. However, the experts have split opinions regarding its confirmatory role. This study explores ADA measurement in cerebrospinal fluid for differentiating TB from other brain infections. The report says that this simple and inexpensive test can be helpful, but it cannot make or refute the diagnosis of brain TB and should only be considered along with other tests.