EVALUATION OF GENE XPERT ASSAY IN EXTRAPULMONARY TUBERCULOSIS IN CHILDREN

Abstract

BACKGROUND Tuberculosis constitutes the main infectious cause of death worldwide. Extra-pulmonary tuberculosis (EPTB) accounts for up to sixty percent of all cases of childhood tuberculosis. In high burden countries like India, WHO in December 2010 endorsed a new rapid test "Gene Xpert MTB/RIF" as a replacement of sputum smear microscopy particularly in smear negative and multidrug resistant TB. We aimed to assess the performance of the Xpert system in diagnosing EPTB in children in a high incidence settings like India and conducted the present study at a tertiary care teaching hospital in New Delhi, India. MATERIALS AND METHODS This is a cross-sectional, hospital-based study. We investigated 60 extrapulmonary clinical specimens with Gene Xpert including 27 (45%) cases of tubercular meningitis, 17 (28%) cases of pleural tuberculosis, 12 (20%) cases of tubercular lymphadenitis, 3 (5%) cases of abdominal Koch's and one (2%) case of pericardial tuberculosis and determined the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of CBNAAT and compared the efficacy of CBNAAT in the rate of detection of Mycobacteria, with the gold standard i.e. Culture (MGIT liquid culture). RESULTS The overall sensitivity of Xpert MTB/RIF was between 50 to 90 percent in various tissue samples while specificity in all samples was approaching almost 100 percent with maximum efficacy in tubercular lymphadenitis where the sensitivity was 90 percent followed by tubercular meningitis with 80 percent sensitivity. CONCLUSION Xpert MTB/RIF was found to be superior in detecting Mycobacterium tuberculosis in Extrapulmonary TB samples with respect to time of result and Rifampicin resistance detection. At present, CBNAAT is being used as a routine test in a suspected Extrapulmonary TB case at our center.