Objective: To describe the factors associated with nonadherence to TB chemoprophylaxis in patients older than 15 years of age treated via referral TB control programs. Methods: A historical cohort study was carried out based on medical charts related to cases treated via referral TB control programs in the city of Vitória, Brazil, between 2002 and 2007. Cases of infection with Mycobacterium tuberculosis were stratified into two groups: health care workers (HCW group); and individuals who were not health care workers (NHCW group). Results: A total of 395 patients were included in the study: 35 in the HCW group and 360 in the NHCW group. The mean age in the HCW and NHCW groups was 34.8 and 32.4 years, respectively (p = 0.36). Of the 35 patients in the HCW group, 29 (82.9%) were female, compared with 180 (50.0%) of the 360 patients in the NHCW group. In the HCW and NHCW groups, respectively, 15 (42.9%) and 169 (46.9%) of the patients were contacts of TB cases. In addition, 9 (25.7%) and 157 (78.5%) the HCW and NHCW group patients, respectively, were HIV-infected. Nonadherence to chemoprophylaxis was 37.1% and 21.9% in the HCW and NHCW groups, respectively (p = 0.045). In the multivariate analysis, the factors associated with nonadherence were being a health care worker (OR = 8.60; 95% CI: 2.09-35.41), being HIV-infected (OR = 4.57; 95% CI: 1.2-17.5) and having had contact with a TB patient (OR = 2.65; 95% CI: 1.15-6.12). Conclusions: In order to improve adherence to TB chemoprophylaxis, new TB control program strategies are needed, especially for health care workers and HIV-infected patients.

Keywords: Tuberculosis; Chemoprevention; Isoniazid.