CSF ADA in Tuberculosis Meningitis Diagnosis

Diagnostic Value of CSF ADA for TB Meningitis

The American Thoracic Society/Infectious Diseases Society of America/CDC guidelines emphasize that ADA levels provide supportive evidence rather than definitive diagnosis and must be interpreted in the entire clinical context 1, 2
CSF ADA is a valuable biomarker for TB meningitis with good sensitivity and specificity when appropriate cut-off values are used 1, 2
According to meta-analyses, CSF ADA has a sensitivity of 79% and specificity of 91% for TB meningitis when using thresholds around 9-10 U/L 1
The diagnostic accuracy of ADA is highly dependent on the threshold used - lower thresholds (around 4 U/L) provide higher sensitivity (>93%) but lower specificity (<80%), while higher thresholds (around 8 U/L) provide lower sensitivity (<59%) but higher specificity (>96%) 2

CSF acid-fast bacilli (AFB) smear microscopy, though sensitivity is low (<5%), can be used as an additional test to confirm TB meningitis 3, 4
CSF mycobacterial culture (sensitivity 45-70%) can be used as an additional test to confirm TB meningitis 3
Molecular tests like PCR for M. tuberculosis can be used as an additional test to confirm TB meningitis 1
Consider measuring free IFN-γ levels in CSF if available 1, 2

Early treatment is crucial as untreated TB meningitis has significant morbidity and mortality 5
A high CSF ADA value should be correlated with clinical presentation, other CSF parameters, and additional diagnostic tests before confirming diagnosis 1, 2