19.146 Point of care urine lipoarabinomannan antigen detection for diagnosis of tuberculosis in Pediatric population

Abstract

Purpose: Due to pauci-bacillary nature of disease, difficulties in obtaining good quality specimen, low sensitivity of smear-microscopy and poor access to culture; rapid diagnosis of tuberculosis in children is challenging. To expedite diagnosis of pediatric tuberculosis, we evaluated Urine Lipoarabinomannan antigen(LAM) detection for its diagnostic accuracy. Young children with pulmonary tuberculosis develop disseminated disease more frequently than adults, which may increase the chances of mycobacterial antigen secretion. Methods & Materials: Based on microbiological and clinical findings, 381 children including 280 and 101 of suspected pulmonary tuberculosis(PTB) and suspected tubercular lymphadenitis(LNTB) were categorized as Confirmed, sixty eight(17.9%) & 25(24.7%); Probable, 66(23.5%) & 20(19.8%); Possible, four(1.4%) & 13(12.8%); and No-TB, 142(50.7%) & 43(42.5%) respectively. In case of PTB, either expectorated sputum or Induced sputum were taken while fine needle aspiration cytology was collected in LNTB. Samples were subjected to Ziehl-Neelsen stain, MGIT-960 culture and GeneXpert. For LAM antigen detection from urine, lateral-flow assay was performed as per manufacturer's instructions. Results: Among the PTB and LNTB cases, Eight(2.8%) and three children(2.9%) were positive by smear, 51(18.2%) and 23(22.7%) by GeneXpert, 48(17.1%) and 9(8.9%) by culture respectively. GeneXpert detected 20 and 16 cases more than culture in PTB & LNTB cases respectively and it detected 31 of 48 culture confirmed PTB cases (sensitivity 74%, specificity 91%) and 7 of 9 culture confirmed LNTB cases (sensitivity 82%, specificity 82%). On analysis of LAM assay with microbiological confirmation (either culture or GeneXpert Positive), sensitivity was 79% & 80%, specificity 71% & 67%, PPV 55% & 52%, NPV 89% & 88% in PTB & LNTB cases respectively. On adding the cases which were started with anti-tubercular therapy irrespective of microbiological confirmation, specificity of LAM assay improved to 92% & 93% and PPV to 93% & 92% in PTB & LNTB cases respectively. Conclusion: GeneXpert assay & Urinary LAM antigen detection led to early detection of TB cases. Nevertheless, neither negative LAM antigen test completely rule out TB nor positive LAM test fully indicates towards tuberculosis. But these limitations were circumvented by good clinical, radiological & histopathological correlation which is needed for treatment initiation and culture continues to be gold standard