Background:  Chile has a TB rate of 19.3 x 10⁵, the lowest in South America, and it has reached the threshold for its eradication as a public health problem. HIV incidence in Chile is 1.5 to 2.0 x 10⁵. Therefore, and in accordance with PAHO guidelines, chemoprophylaxis in HIV⁺ patients is  focused to latent TB or contacts. In late 2001 a national expanded access program to ART was begun, reaching 100% coverage by August 2003 (4178 patients) in the public health system (which cares for 70% of the population). Close to 80% of these patients are being followed prospectively as the ChiAC. The purpose of this study is to compare TB rates and associated risk factors in the general and HIV population and the early impact of ART on TB.

Methods:  Analysis of the ChiAC TB data base as compared with national general statistics on TB.

Results:  According to national guidelines all pts with HIV and TB have indication of ART but only 55% of all HIV patients meet ART criteria;  139 of the first 1704 (8.2%) HIV patients on ART, who were properly followed-up, had TB before ART and it is thought to represent most of the coinfected cases due to early enrollment to ART, so the rate range could go from 8.2% (observed) to 4.6% (if all TB cases of the cohort were already in treatment).

The national TB program and ChiAC have a registry of associated factors. Some characteristics of the  general population regarding HIV and TB, respectively, are as follows:  male, 58% and 88%;  pulmonary TB, 72% and 69.5%; extrapulmonary TB, 27.7% and 30%. Age distribution is spread in the general population with TB and concentrated  in the 25- to 44-year-old group in HIV-TB mimicking the HIV epidemics; educational level is higher in HIV-TB cases. Mean CD4 in pulmonary and extrapulmonary HIV-TB was similar: 65.4 x mm³ (0 to 296) and 95.7 (0 to 282), respectively. During the first 6 months of ART, TB rates decreased from the observed accumulated 8.2% before ART to 1.2%.

Conclusions:  The AIDS epidemic is affecting Chile while its general TB rate is decreasing markedly, but the TB rate among HIV patients is at least 100 times higher than that in the rest of the population. ART is contributing significantly to bring that higher rate down, even early after its initiation, so contributing to the steadly decreasing rate of TB in the country.

Keywords: tuberculosis; antiretroviral therapy; developing country