Comparison Study of GENEXPERT versus TB MGIT Culture in Extra Pulmonary Tuberculosis

Abstract

Aims and objectives: To compare the diagnostic yield of Extra Pulmonary Tuberculosis, in terms of MTB isolation & detection of drug resistance via GENEXPERT & MGIT-DST culture methods. Materials and Methods: This was a prospective observational study carried out in Department of Pulmonary medicine, D.Y. Patil Hospital, Navi Mumbai. Study participants were patients above 18 years of age who had extra pulmonary tuberculosis and who were not already on Anti tuberculosis treatment in D.Y. Patil Hospital, Nerul, Navi Mumbai and willing to participate in the study and meeting all the inclusion criteria of the study. Study duration was from the date of approval by institutional ethics committee to October 2019.Sample size was 150 patients satisfying the inclusion criteria. Results: In our study, 28 % of all extra pulmonary samples were tested positive for TB MGIT culture out of which 35.2 % showed Resistance to 1st line ATT drugs on DST where as 39.33% was tested positive with Gene expert out of which 22.47% showed Rifampicin Resistance. Sensitivity of MGIT was 28.00 % and specificity was 39.50 %.Sensitivity of Genexpert was 39.33% and specificity was 26.5%. Conclusion: Our findings suggest that Gene Xpert may have a role in EPTB diagnosis in addition to PTB, particularly in low income/high-burden settings, where facilities for mycobacterial culture are limited. But Gene Xpert can detect only Rifampicin resistance where as DST by BACTEC MGIT AFB Culture detects other ATT drugs sensitivity too. Also the test results of MTB detected in GeneXpert in extra pulmonary samples was shown as low and very low based on the CT range (high, 28) as most of the extra pulmonary samples are pauci bacillary; hence the result is not totally reliable. Therefore, it should be confirmed by phenotypic DST by BACTEC MGIT Culture.