Survival and Predictors of Death after Successful Treatment among Smear Positive Tuberculosis: A Cohort Study

BACKGROUND: Tuberculosis (TB) can affect patients’ life even after successful treatment. In this study, we aimed to determine the survival rate of patients with smear positive TB after successful treatment and identify the predictors of mortality. METHODS: This was a prospective study. The source of data was the TB registry system in Iran and 964 patients were eligible for the study. The life table was used to determine the annual survival rate. Survival curves were estimated using Kaplan–Meier and were compared using the log-rank test. In order to determine the predictors of survival, four models of Cox regression, exponential, Weibull and log-logistic fitted and finally exponential model with minimum akaike information criteria and Bayesian information criterion values were selected. Then, variables with significant levels <0.2 in univariate analysis were entered into the multivariate model. Hazard ratios with a confidence interval of 95% were used to measure the association. RESULTS: A total of 149 patients (15.5%) died during the follow-up period. The median of survival time after successful treatment was 10.5 years and survival probability for 11 years after successful treatment was 70%. Furthermore, previous TB treatment, high age, suffering from kidney failure and cancer were predictors of mortality after successful treatment. CONCLUSIONS: This study showed that positive smear pulmonary tuberculosis even after successful treatment has an adverse effect on the patients’ survival and leads to a decrease in their survival rate in the long run. Furthermore, individuals with a history of previous TB treatment had much lower survival rates.