Adenosine Deaminase

Measurement of adenosine deaminase (ADA) in pleural fluid may be helpful in the differential diagnosis of malignant versus a tuberculous pleural effusion when the diagnosis cannot be made from cytology, smear or culture.

ADA testing is most valuable in ruling out tuberculosis in geographic locations with a lower prevalence of disease. It can be used to rule in tuberculous pleurisy in regions with high prevalence of tuberculosis.

ADA levels are typically greater than 35 to50 U/L in tuberculous pleural effusions. Specificity for tuberculosis is increased when the lymphocyte to neutrophil ratio is greater than 0.75 and the ADA is greater than 50 U/L. False negatives and positive ADA results do occur, so ADA results need to be interpreted along with other laboratory and clinical findings.

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