Performance of the quantification of adenosine deaminase and determination of the lactate dehydrogenase/adenosine deaminase ratio for the diagnosis of pleural tuberculosis in children and adolescents

OBJECTIVE: To evaluate the accuracy of determining the adenosine deaminase (ADA) level, the 2’-deoxyadenosine/ADA ratio, and the LDH/ADA ratio in pleural fluid for the diagnosis of pleural tuberculosis (PT) in children and adolescents. METHODS: This was a retrospective cross-sectional study conducted at a tertiary hospital in a high-tuberculosis-incidence area, between 2001 and 2018. All patients with ADA in pleural fluid and a confirmed diagnosis of PT (cPT) or parapneumonic effusion (PPE) were included. RESULTS: The cPT and PPE groups comprised 25 and 68 individuals, respectively. At a cutoff of 40 U/L, ADA measurement showed the following: sensitivity, 88%; specificity, 31%; positive predictive value (PPV), 32%; negative predictive value (NPV), 88%; and overall accuracy, 46%. The best cutoffs were an ADA level of 125 U/L, a 2’-deoxyadenosine/ADA ratio of 0.5, and an LDH/ADA ratio of 8.3, with AUC of 0.67, 0.75, and 0.82, respectively. The sensitivity, specificity, PPV, NPV, and overall accuracy of the 125 U/L ADA cutoff were 84%, 65%, 47%, 92%, and 70%, respectively, compared with 79%, 79%, 59%, 91%, and 79%, respectively, for the 8.3 LDH/ADA ratio cutoff. Changing the LDH/ADA ratio cutoff to 3.0 increased the specificity to 98%. CONCLUSIONS: The ADA level and the 2’-deoxyadenosine/ADA ratio are not good biomarkers for the diagnosis of PT in pediatric patients. Determination of the LDH/ADA ratio provides the best overall accuracy for the diagnosis of PT in such patients.