Diagnosis of pediatric pulmonary tuberculosis with special reference to polymerase chain reaction based nucleic acid amplification test

Abstract

Objective: To determine the utility of polymerase chain reaction (PCR) for diagnosing pediatric pulmonary tuberculosis (PPTB). Method: A prospective cross-sectional study was carried out on 100 children less than 14. years of age, with strong clinical suspicion and radiological evidence suggestive of pulmonary tuberculosis (TB). Sputum samples/gastric lavage were collected. Direct smears and culture on Lowenstein Jensen (LJ) media were performed. DNA extraction and amplification was performed using Genei™ Amplification Reagent set for Mycobacterium tuberculosis (MTB) (by Genei, Bangalore, India). This test is based on the principle of single-tube nested PCR which amplifies the repetitive insertion sequence IS6110. Results: When compared with culture, sensitivity and specificity of PCR was 93.55% and 92.75%, respectively. The PPV was 85.29% and the NPV was 96.97%. When intention to treat (ITT) was used as the standard, sensitivity, specificity, PPV and NPV of PCR was 47.88%, 93.1%, 94.4%, and 42.19%, respectively, and that of culture was 40.85%, 100%, 100% and 40.85%, respectively. Against response to treatment (RTT), PCR demonstrated sensitivity, specificity, PPV and NPV of 50.9%, 93.1%, 93.33% and 50%, respectively, and for culture it was 43.64%, 100%, 100% and 48.33%, respectively. Conclusion/recommendation: The present study reinforces better case detection rate with PCR-based nucleic acid amplification test as compared with microscopy and culture in pediatric pulmonary TB. PCR showed a higher correlation with clinical diagnosis as compared with microscopy and solid culture. Hence, a molecular platform should be the test of choice for detecting PPTB.