Interpretation of Pleural Fluid ADA Levels in Tuberculosis Diagnosis

Diagnostic Role of ADA

In high‑TB‑prevalence settings, pleural fluid ADA can be used as a supportive test for tuberculous pleural effusion, but tissue sampling remains the preferred diagnostic approach (British Thoracic Society) 1.
An ADA concentration of 24 U/L lowers the probability of tuberculous pleural effusion but does not exclude it (Infectious Diseases Society of America) 3.
In low‑TB‑prevalence populations, ADA serves primarily as an exclusion test for tuberculous pleural effusion (British Thoracic Society) 2.

Regardless of the ADA result, pleural tissue sampling for culture and sensitivity is the recommended definitive diagnostic method for suspected tuberculous pleural effusion (British Thoracic Society) 1.
Thoracoscopic or image‑guided pleural biopsy should be performed when clinically indicated and when resources allow (British Thoracic Society) 2.
Blind (non‑image‑guided) pleural biopsies are discouraged because of lower diagnostic yield (British Thoracic Society) 2.

ADA measurement does not provide a definitive diagnosis; it must be interpreted within the broader clinical context (Infectious Diseases Society of America) 4.
False‑negative ADA results can delay appropriate therapy, while false‑positive results may lead to unnecessary anti‑tuberculous treatment and associated drug toxicity (Infectious Diseases Society of America) 5.

For tuberculous meningitis, cerebrospinal fluid ADA thresholds of 9–10 U/L yield a sensitivity of ~79 % and specificity of ~91 % (Infectious Diseases Society of America) 3.

Serum ADA is not routinely employed for diagnosing tuberculous pleural effusion, but it may be considered as an adjunctive test in high‑prevalence regions (British Thoracic Society) 1.