Analysis of the Effectiveness of Gene Xpert Test in Targeted Screening and Primary Diagnostic Algorithms for Mycobacterium Tuberculosis Infection and Rifampicin resistance in manicaland, Zimbabwe, 2017-2018

Abstract

Early Tuberculosis (TB) detection and early TB treatment are the backbone of breaking TB transmission cycle. Zimbabwe is a triple disease burden country with TB, HIV and multi drug resistant TB. In 2014 the World Health Organization recommended that Xpert Mycobacterium tuberculosis/Rifampicin (XMTB/R) be used as a primary diagnostic algorithm on all presumptive TB patients. Zimbabwe adopted XMTB/R primary diagnostic algorithm in 2016. In Manicaland the transition from XMTB/R targeted algorithm to XMTB/R primary diagnostic algorithm occurred in phases and was complete by 1st quarter 2018. However, this intervention had not been systematically evaluated in Zimbabwe. Evaluation of effectiveness of XMTB/R primary diagnostic algorithm MTB positive result pick up rate in Zimbabwe, was essential. The objective of the study was to analyse the effectiveness of Gene Xpert test in targeted screening and primary diagnostic algorithms for MTB infection and rifampicin resistance under the National TB programme in Manicaland, one of the affected provinces in Zimbabwe. This was a retrospective analysis of cohort data for National TB program presumptive TB patients’ sputum results obtained 2017-2018. Categorical variables were described using frequencies, measure of association for quantitative variables using Pearson statistic and measure of agreement using cohen kappa. The level of significance was p value <0.05, at 95% confidence interval using z-score 1.96. Out of 43 809 patients’ data downloaded, 36 056 had data acceptable for enrolment, while 15 719 smear microscopy patients’ data were enrolled. Of the 36 056 XMTB/R patients’ data, 5 769/36 056 (16.0%) were tested for TB using XMTB/R targeted screening algorithm versus 30 286/36 056 (84.0%) tested using XMTB/R primary diagnostic algorithm. The MTB positive result pick up rate for XMTB/R targeted screening algorithm and MTB positive result pick up rate for XMTB/R primary diagnostic algorithm was 430/36 056 (1.2%) and 1 791/ 36 056 (5.0%), respectively. The MTB positive result pick up rates decreased from 8.3%, in the 1st quarter of 2017 to the lowest rate of 4.8% in the 4th quarter of 2018. Rifampicin resistance detection was found in 111/2 221(5.0%), p value <0.001. Mean laboratory turnaround time improved from 1.7 ± 0.4 days in the targeted screening algorithm to 1.4 ± 0.8 days (p<0.001) in the primary diagnostic algorithm. From 1st quarter 2017 to 4th quarter 2018 the initial TB diagnosis based on MTB detected moved from 49/281 (17.4%) to 332/534 (62.2%) p value <0.001. Using GxAlert increased the capacity for geo-spatial mapping of downloaded MTB cases, with Chipinge District in Manicaland having the second highest frequency of MTB mapped [11/15 (73.3%) of its health facilities]. Buhera District had the highest proportion of 10/13 (76.9%) health facilities with rifampicin resistance mapped. In conclusion the number of TB cases detected increased and there was a statistically significant increase in detection of rifampicin resistance. Recommendation is sustained provision of the XMTB/R primary diagnostic algorithm intervention, to enable early TB detection can break the TB transmission cycle.