Adenosine deaminase cutoff value when diagnosing tuberculous pleurisy in patients aged 40 years and older

INTRODUCTION: Tuberculous pleurisy (TBP) is one of the most common manifestations of extra-pulmonary tuberculosis. In patients aged ≥40 years, a closed needle pleural biopsy is recommended with an adenosine deaminase (ADA) level of 40-70 U/L. We aim to investigate whether the cutoff value of ADA and the cancer ratio in patients with TBP aged ≥40 years is different and determine the effects of both compounded biomarkers on diagnosing TBP. MATERIALS AND METHODS: Between 2009 and 2016, the ADA levels were measured in pleural effusions from patients who were admitted to the Chest disease clinic. RESULTS: Of the 196 patients included in the study, 104 were aged ≥40 years. A significant relationship was found between the serum LDH/pleural ADA (sLDH/pADA) ratio and ADA levels in patients aged >40 years (OR: 0.935 and OR: 1.085, respectively). The model using an ADA value ≥30 and an sLDH/pADA ratio <16 yielded a sensitivity of 94.25% (95% CI, 87.1-98.10) in all patients and 69.23% (95% CI, 54.9-81.28) in patients aged >40 years. CONCLUSION: ADA and the sLDH/pADA ratio are simple, cost-efficient, and obtain fast results and, therefore, are the preferred methods in TBP diagnosis. The diagnosis rate in the present study was 91% using ADA levels in combination with the sLDH/pADA ratio, both of which can be obtained only through thoracentesis.