Factors influencing pleural adenosine deaminase level in patients with tuberculous pleurisy.

BACKGROUND:Adenosine deaminase (ADA) activity is useful for diagnosing tuberculous (TB) pleurisy in regions with a high prevalence of tuberculosis. However, some cases of TB pleural effusion show decreased ADA activity. Therefore, we evaluated factors influencing pleural ADA levels in patients with TB pleurisy. METHODS:We retrospectively evaluated 182 patients with TB pleural effusion who were admitted to Gyeongsang National University Hospital from January 2004 to September 2008. Patients were dichotomized into 2 groups: a low-ADA (<40 IU/L) group (n = 22) and a high-ADA (≥40 IU/L) group (n = 160). Age, sex, ADA level of pleural effusion, smoking status, history of tuberculosis and comorbid diseases were evaluated in each group. RESULTS:The median age of the patients was 50.5 years, with a male to female ratio of 1.72:1. Patients with a low-ADA level were significantly older than those with a high ADA level (66.9 ± 12.0 versus 49.4 ± 21.2 years, P < 0.001). A history of tuberculosis and hypertension was more common in the low-ADA group than in the high-ADA group (31.8% versus 15.0%, P = 0.049 and 36.4% versus 16.9%, P = 0.03, respectively). A multivariate analysis revealed that older age and current smoking were predictive of TB pleurisy with a low ADA level (odds ratios, 1.053 and 4.848; P = 0.002 and 0.028, respectively). CONCLUSIONS:Physicians should be careful when interpreting pleural ADA levels in elderly patients and/or current smokers for the diagnosis of TB pleurisy.