Diagnostic performance of adenosine deaminase activity in pleural fluid: a single-center experience with over 2100 consecutive patients.
OBJECTIVE
To determine the diagnostic utility of adenosine deaminase (ADA) in a large series of pleural effusions of different etiologies.


METHODS
A retrospective study of 2104 consecutive patients presenting with pleural effusion was carried out at a Spanish university hospital. ADA levels in pleural fluid were determined using a non-Giusti automatic kinetic assay, and a receiver operating characteristics curve analysis was applied to estimate their discriminative properties.


RESULTS
Pleural tuberculosis (TB) accounted for 221 (10.5%) effusions. Pleural fluid ADA >35U/L yielded 93% sensitivity, 90% specificity, a positive likelihood ratio (LR) of 10.05 and a negative LR of 0.07 for the diagnosis of TB among lymphocytic exudates. The ADA activity was significantly higher in neutrophil- (111.6U/L) than in lymphocyte-rich (62.4U/L; p=0.002) TB effusions. Overall, more than 40% of parapneumonics and half of lymphomatous effusions exceeded the cutoff set for TB. These were the only causes of ADA activity above 250U/L. When the prevalence of TB as a cause of exudative effusions is low (e.g., 1%), the estimated positive predictive value of the ADA test may be as low as 7%, although the negative predictive value remains high (99.9%).


CONCLUSIONS
Where available, pleural ADA should be routinely used to rule TB in or out in areas with moderate to high or low TB prevalence, respectively. A high ADA level is a characteristic not only of lymphocytic, but also of neutrophilic TB effusions. An extremely high ADA activity should raise suspicion of empyema or lymphoma.
Porcel
José M
JM
Pleural Diseases Unit, Department of Internal Medicine, Arnau de Vilanova University Hospital, Institut de Recerca Biomèdica de Lleida, Avda. Alcalde Rovira Roure 80, Lleida, Spain. jporcelp@yahoo.es
Esquerda
Aureli
A
Bielsa
Silvia
S
D000243:Adenosine Deaminase / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000378:metabolism*; D004653:Empyema / Q000175:diagnosis / Q000453:epidemiology / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D005189:False Positive Reactions; D006801:Humans; D008223:Lymphoma / Q000175:diagnosis / Q000453:epidemiology / Q000378:metabolism; D008875:Middle Aged; D016066:Pleural Effusion, Malignant / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism*; D011237:Predictive Value of Tests; D015995:Prevalence; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014396:Tuberculosis, Pleural / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism*; D055815:Young Adult
D015415:Biomarkers; C548482:ADA protein, human; D000243:Adenosine Deaminase