Predictors of poor treatment outcome in multi- and extensively drug-resistant pulmonary TB

Treatment outcome in multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) is often unsuccessful, but the particular determinants of poor treatment outcome have remained obscure. The present authors therefore analysed treatment effectiveness and predictors of poor treatment outcome in pulmonary MDR-TB and XDR-TB in Estonia, a European country with one of the highest MDR-TB and XDR-TB rates in the world. All culture-confirmed pulmonary MDR-TB and XDR-TB patients who started TB treatment in 2003-2005 were included. Multivariate analysis was performed on two models of predictors: 1) patients' HIV-status, demographic and socioeconomic characteristics; and 2) TB-related data. In the 235 MDR-TB patients, the proportion of overall successful treatment outcome was 60.4%, rising to 72.8% among adherent patients. Among the 54 XDR-TB patients, these proportions were 42.6% and 50.0%, respectively. Risk factors for poor treatment outcome in MDR-TB were HIV infection, previous TB treatment, resistance to ofloxacin and positive acid-fast bacilli (AFB) smear at the start of treatment. Predictors of poor treatment outcome in XDR-TB were urban residence and positive AFB smear. This country-wide study provides evidence that to improve treatment outcome in multidrug-resistant and extensively drug-resistant tuberculosis, special care should be taken to treat HIV-infected patients and urban residents, as well as to make efforts to diminish re-treatment cases by increasing patient adherence.