Impact of Xpert MTB/RIF assay on multidrug-resistant tuberculosis treatment outcomes in a health district in South Africa

Abstract

Background. Xpert MTB/RIF assay rapidly diagnoses rifampicin resistance, enabling early initiation of second-line tuberculosis (TB) treatment. However, the impact of an earlier multidrug-resistant TB (MDR-TB) diagnosis on treatment outcomes is unknown.

Objectives. To compare MDR-TB treatment outcomes in cases diagnosed with smear/culture and Xpert.

Methods. This was a retrospective cohort study with cohorts defined by the diagnostic assay used in presumptive TB cases. Data were extracted from a drug-resistant (DR)-TB register including cases from January 2012 to June 2014. Treatment outcomes were assessed at recorded endpoints or after 2 years for those completing treatment.

Results. A total of 718 cases were enrolled into the study. Cure rates were 43.4% (n=158) for the smear/culture cohort and 33.5% (n=118) for the Xpert cohort (p<0.01). Xpert diagnosis (adjusted risk ratio (aRR) 0.65; p=0.02) and male gender (aRR 0.66; p=0.04) were associated with cure outcome. Xpert diagnosis increased time to sputum culture conversion from 4 to 5 months (log-rank test p=0.01). Time to treatment initiation was not associated with treatment success in logistic regression analysis.

Conclusions. Despite rapid treatment initiation, MDR-TB treatment outcomes were poorer in patients diagnosed with Xpert MTB/RIF assay than in the smear/culture cohort, and they were also poorer in men than in women. Additional studies are required to assess possible factors influencing DR-TB outcomes.