Tuberculosis recurrence and its associated risk factors among successfully treated patients

Little is known about recurrent tuberculosis (TB) in developed countries. The objective of this study was to determine the probability of TB recurrence and the associated risk factors among cured patients in a city with moderate TB incidence.

A population-based retrospective longitudinal study was carried out in Barcelona, Spain. All patients with culture-confirmed TB and drug susceptibility testing were included between 1995 and 1997 and followed until December 2005. The authors defined recurrence as a new TB event after a patient was considered cured and had remained free of the disease for a minimum of 1 year. Kaplan-Meier and Cox regression were used in the statistical analysis. HRs with 95% CIs were calculated.

Among the 681 patients studied, the authors observed 29 recurrences (recurrence rate 0.53/100 person-years of follow-up). The mean incidence of TB in Barcelona from 1995 to 2005 was 36.25 cases per 100,000 inhabitants. The incidence of recurrence was 14.6 times higher in the cohort than the incidence of a first TB episode in the general population. The factors associated with recurrence at bivariate level were being male, being an immigrant, being an intravenous drug user (IDU), having human immunodeficiency virus, smoking, being an alcoholic, being in prison, and having both pulmonary and extrapulmonary TB. At multivariate level, only being an immigrant (HR 3.2, 95% CI 1.2 to 9), an IDU (HR 2.9, 95% CI 1.3 to 6.4) and male (HR 4.3, 95% CI 1.3 to 14.6) were associated.

Having TB in the past is a risk factor for developing TB. Social policies must be implemented in populations at risk of recurrence, especially in immigrants and IDUs.