EVALUATION OF GENEXPERT MTB/RIF ASSAY OVER FLUORESCENCE MICROSCOPY FROM TUBERCULOSIS SUSPECTED PATIENTS OF CENTRAL REGION NEPAL

Abstract

Tuberculosis is one of the major public health problems worldwide and especially in developing countries like Nepal, and occurrence of drug-resistant is more challenging. The rapid detection of tuberculosis bacteria and drugs resistance permits the establishment of an effective treatment regimen, minimizes the risk of further resistance development and limits the spread of drug-resistant Mycobacterium tuberculosis strains. The Xpert MTB/RIF test is a fully automated nucleic acid amplification test for the detection of MTB DNA and rifampicin resistance associated mutation in rpoB gene that provides the result within 2 hours. The present study was aimed to evaluate the performance of Xpert MTB/RIF assay over fluorescence microscopy from tuberculosis suspected patients visiting GENETUP, Kathmandu. The clinical samples, both pulmonary and extrapulmonary, were collected, processed and examined in the laboratory of GENETUP. The collected samples were examined by Fluorescence microscopy (FM) method and by Xpert MTB/RIF assay for the presence of acid-fast bacilli Mycobacterium tuberculosis and its resistance to rifampicin, one of the effective anti-TB drugs. Out of 451 suspected samples 177 (39.25%) were detected with the disease and among them 10 cases were found to be rifampicin-resistant TB (RR-TB). Higher proportion of males (60.5%) was detected with TB and which was found to be more in the mid age groups 20-40 years. The sensitivity of Xpert MTB/RIF assay was found to be 95.1% and it detected 79 more MTB cases in smear negative samples than detected by FM; while specificity of Xpert MTB/RIF was found to be 77.3%. Likewise, the sensitivity and specificity of Xpert MTB/RIF assay for PTB samples were 96% and 79.4%, and that for EPTB samples were 80% and 51.9% respectively. The failure of Probe E hybridization denoted the occurrence of mutation and presence of RR-TB. Xpert MTB/RIF assay can be effectively used for the rapid detection of TB and mutation in the gene responsible for rifampicin-resistance.