Thirteen studies (n=380) were included: four prospective and nine retrospective studies. Nine studies enrolled consecutive patients and four studies enrolled a random sample. Test interpretation was blinded in three studies.
Using thresholds defined by the study authors, summary sensitivity was 74% (95% CI 69% to 79%) and summary specificity was 87% (95% CI 85% to 90%). Results were reported for other thresholds. There was substantial heterogeneity between studies (p<0.001).
Mean adenosine deaminase level in patients with tuberculous meningitis was 11.50U/L (standard deviation (SD) 7.90) and 11.80U/L (SD 10.70) in patients with bacterial meningitis. Mean adenosine deaminase level in patients with meningitis other than bacterial types was 3.00 U/L (SD 4.2).
At a threshold of 10U/L the diagnostic odds ratio for tuberculous meningitis compared to bacterial meningitis was 1.10 (95% CI 0.65 to 1.84), which suggested no discriminatory power. The diagnostic odds ratio for tuberculous meningitis compared to other non-bacterial meningitis at the same threshold was 112 (95% CI 88.9 to 145.8), which suggested excellent diagnostic performance.