A study on the role of cartridge based nucleic acid amplification test (cbnaat) and mantoux test for diagnosis of pediatric tuberculosis

Introduction: India accounts for one-fifth of the global tuberculosis (TB) incidence, with TB remaining one of the leading causes of childhood mortality and morbidity. Bacteriological confirmation of TB in children is challenging due to difficulty in obtaining quality specimens, in the absence of which diagnosis largely depends on clinical judgement. Lack of high sensitivity tests adds to the diagnostic challenge. This study focuses on finding the sensitivity, specificity, positive predictive value and negative predictive role of CBNAAT for diagnosis of TB in pediatric population in pulmonary and extra pulmonary specimens.
Methodology: The study was done in the new hospital medical college unit of department of Pediatrics, Govt. Medical College , Kota Rajasthan. from July 2017 to July 2019. A tota of 130 patients presenting with symptoms & signs of suspected pulmonary or extrapulmonary tuberculosis or having history of contact with diagnosed tuberculosis patients admitted in our unit during the study period were included in this study. Samples (pulmonary and extrapulmonary) were collected from the subjects and put to test for CBNAAT. Mantoux test was done in all suspected cases & interpretation done at 48 hours of injection. Presence of BCG scar was noted as a proof of BCG Vaccination. Other haematological & radiological investigations were done as per requirement.
Results: A total of 130 cases of suspected Tuberculosis were subjected for CBNAAT test in the study. Majority patients belonged to the age group of 0 to 5 years ( 60%). Remaining 23% were in age group of 5 to 10 years & 16.9% in the ages between 10 to 18 years.Males were more affected than females (45%). Most common form of Pediatric Tuberculosis cases in the study was the Progressive Pulmonary tuberculosis, 2 cases were of TB Lymphadenitis, 4 cases of TB Meningitis, 2 with Tuberculoma with seizures, 2 cases of Abdominal TB & one case presented with Acute Pain Abdomen with TB salpingitis in an adolescent girl of 16 years. Miliary tuberculosis was seen in 2 cases. While 8 cases reported with Tubercular Pleural effusion. One with TB of Dorsolumbar spine & Gibbus. Most of the patients presented with fever & cough > 2 weeks (78%), 85% presented with weight loss/ no weight gain & Anorexia. Out of these 12(63.15%) patients had a positive Mantoux Test while 7(36.84%) patients with a positive CBNAAT had a negative MT.BCG scar was not present in19 cases. 17 patients (15.39%) with CBNAAT detected had a BCG scar while 94 cases with a BCG scar did not have MTB detected by CBNAAT. Only 2 patients with positive CBNAAT did not have a BCG scar (10.5%).
Conclusion: CBNAAT assay is a rapid test which identifies both the presence of Mycobacterium tuberculosis (MTB). It also correlates well with Mantoux Positivity in Pediatric Population.