Introducing molecular testing of pyrazinamide susceptibility improves multidrug-resistant tuberculosis treatment outcomes: a prospective cohort study.

The current treatment for multidrug-resistant tuberculosis (MDR-TB) takes a lengthy period of 18-24 months and has a poor cure rate of 50-60%. A multicenter, prospective cohort study was conducted to assess the role of testing for molecular susceptibility to pyrazinamide (PZA) in optimising treatment for MDR-TB.We assigned 76 patients to an optimised molecular susceptibility group and 159 patients to a regular treatment group where PZA susceptibility was not determined. Of these patients, 152 were matched after propensity score matching (76 in the optimised group and 76 in the regular group). Treatment success rate was measured in the propensity-matched cohort as the primary outcome.Patients in the optimised group achieved a higher treatment success rate than those in the regular group (76.3% versus 55.3%, p=0.006). Of 51 patients with isolates that were susceptible to PZA and who were receiving a 12-month regimen, 42 (82.4%) were treated successfully. The optimised group showed faster culture conversion than the regular group (p=0.024). After exclusion of pre-extensively drug-resistant TB (pre-XDR-TB), the treatment outcome in the optimised group was still better than the regular group (83.1% versus 62.1%, p=0.009).Introducing molecular susceptibility testing for PZA improved the treatment outcomes for MDR-TB without the use of new drugs. Introducing PZA for patients with PZA-susceptible (PZA-S) MDR-TB allows the current regimen to be shortened to 12 months with comparable success rates to the World Health Organization (WHO) recommended shorter regimen.