Abstract

Isoniazid (INH) is an essential drug for tuberculosis (TB) treatment and resistance to INH may increase the likelihood of negative treatment outcomes. We aimed to determine the impact of INH mono-resistance on TB treatment outcomes in the European Union/European Economic Area (EU/EEA) and identify factors associated with unsuccessful treatment of patients with INH mono-resistant TB.

We analysed TB cases reported in EU/EEA countries with information on treatment outcome and drug susceptibility that were diagnosed between 2002-2014 and included in the European Surveillance System. Multilevel logistic regression models were applied to correct for clustering of cases within countries.

A total of 187,370 fully susceptible and 7,578 INH mono-resistant TB cases from twenty-four EU/EEA countries were included in the analysis. Treatment was successful at 12 months after diagnosis in 67.7% of INH mono-resistant and in 75.8% of fully susceptible TB cases (P<0.01). Adjusted for other variables INH mono-resistance was significantly associated with lower treatment success (odds ratio 0.60; 95% confidence interval 0.41-0.86). Among INH mono-resistant TB cases, unsuccessful treatment outcome was significantly associated with age above the median age (41 years), being born in or having citizenship of the country reporting the case, positive smear microscopy, positive HIV status and having a history of TB.

This study confirms the adverse impact of INH mono-resistance on TB treatment success. Increased efforts are needed to improve treatment and management of INH mono-resistant cases.