Tuberculosis incidence in a cohort of individuals infected with human T-lymphotropic virus type 1 (HTLV-1) in Salvador, Brazil

BACKGROUND: Few reports have investigated the association between human T-lymphotropic virus type 1 (HTLV-1) and tuberculosis (TB) in countries where both infections are endemic. This study estimates the incidence of TB in a cohort infected with HTLV-1, compared with non-infected individuals, over a ten-year period. METHODS: Retrospective cohort study involving the cross-matching of records of individuals for whom a HTLV serology was performed at a referral center for HTLV (CHTLV) with a database of TB cases from Sinan—the Information System on Diseases of Compulsory Declaration between 2002 and 2012. RESULTS: From a cohort of 6,495 individuals, 1,711 were infected with HTLV-1. A total of 73 TB cases occurred during the study period: 33 HTLV-1-infected patients and 40 uninfected individuals. The incidence density for TB in the HTLV-1 infected group was 3.3 person-years per 1,000 individuals and 1.1 person-years per 1,000 individuals in the group HTLV-1 uninfected group. The relative risk of developing TB in the group of patients infected with HTLV-1 was 2.6 (CI 95 % 1.6–4.2) in comparison with HTLV-1 uninfected group. Compared to individuals with isolated TB, those in the HTLV-1 infected group who had TB were older (p = 0.005) and had lower education levels (p = 0.02). No differences were observed with respect to the clinical/radiological presentation, nor in the outcome of TB and prevalence of HIV infection, when comparing among the HTLV-1-infected and uninfected groups. CONCLUSIONS: Patients infected with HTLV-1 are more susceptible to TB. The epidemiological characteristics of HTLV-1/TB subjects and those infected with TB overlap.