M. Tuberculosis 85b messenger ribonucleic acid as a biomarker for treatment response among multidrug resistant tuberculosis patients attending Mulago hospital, Uganda
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Background: The occurrence of multidrug resistance (MDR) is one of the major bottlenecks to TB elimination. This is worsened by the lack of reliable point of care (POC) tests for monitoring MDR TB patients with viable M. tuberculosis (Mtb) bacilli during treatment course. This study aimed at evaluating the performance of M. tuberculosis 85B mRNA from sputum, as a measure for treatment response among MDR TB patients during the initial 12 weeks of treatment using MGIT-culture time to positivity as a reference standard. Methods: 60 GTC/TRIzol preserved sputum samples from 20 MDR TB participant collected at week0, week8 and week12 by the mother study (MDRTB-Tx Monitor), were used to run qRT-PCR assays (7500 AB RT-PCR system) targeting Mtb 85B gene . Data from qRT-PCR assay was compared to MGIT-TTP data, as well as patient data provided by the mother study. Data analysis was done in SPSS software (IBM SPSS VERSION 21 and MS Excel 2010) using correlation methods, regression methods, one way ANOVA, ROC analysis, and Wilcoxon signed rank test. Results: Mean qRT-PCR Cts increased with increase in MGIT-TTP (R2=0.998), a significant fair but negative correlation between week0 MGIT-TTP and qRT-PCR Cts (-0.473, p<0.035, spearman’s rho), about 44% conversion rate from week0 to week8 (Z score of -2.000, p=0.046 wilcoxon’s test and correlation of 0.444, p=0.05 spearman’s rho) were observed. ROC analysis determined that a cut-off Ct value of 37.9 was ideal at predicting week8 conversion. No significant relationship was observed between 85B Mtb mRNA with the studied patient factors. However, one way ANOVA mean plots demonstrated good performance of the study biomarker in participants with alcohol history, previous TB diagnosis, no fever, smokers and nonsmokers, female and HIV positive participants, in middle age group, participants with very bacillary loads by XpertMTBRif assay, and in +3, +2 by CFM smear microscopy. Conclusion: M. tuberculosis 85B mRNA is promising prognostic biomarker. However, there is need for more investigations on this biomarker in larger sample size MDR TB studies to come up with a more reliable statistically sound scientific conclusion.