Relatedness and HLA-DRB1 typing may discriminate the magnitude of the genetic susceptibility to tuberculosis using a household contact model.

BACKGROUND: Tuberculosis clusters in families may be due to increased household exposure, shared genetic factors, or both. Household contact studies are useful to control exposure because socioeconomic and environmental conditions are similar to all subjects, allowing the evaluation of the contribution of relatedness to disease development. METHODS: In this study, the familial aggregation of tuberculosis using relatedness and a specific inherited marker (HLA-DRB1) was evaluated. Fifty families, which had at least two cases of tuberculosis diagnosed within the past 5 years, were selected from a cohort of tuberculosis carried out in Recife, Brazil. The first case diagnosed was considered to be a primary case. The secondary attack rate of tuberculosis in household contacts was estimated according to the degree of relatedness. The relative risk of having tuberculosis based on the degree of relatedness household and the population attributable fraction to relatedness were also estimated. HLA-DRB1 typing and attributable etiologic/preventive fractions were calculated among sick and healthy household contacts. RESULTS: Compared to unrelated contacts, the relative risk for tuberculosis adjusted for age was 1.38 (95% CI 0.86 to 2.21). Relatedness contributed 23% to the development of tuberculosis at the population levels. The HLA-DRB1*04 allele group (OR=2.44; p=0.0324; etiologic fraction=0.15) was overrepresented and the DRB1*15 allele group (OR=0.48; p=0.0488; protective fraction=0.19) was underrepresented among household contacts exhibiting tuberculosis. The presence of DRB1 shared alleles between primary cases and their contacts was a risk factor for tuberculosis (p=0.0281). CONCLUSION: This household contact model together with the utilisation of two genetic variables permitted the evaluation of genetic factors contributing towards tuberculosis development.

[Surveillance of endemic diseases in urban areas: the interface between census tract maps and morbidity data]. / Vigilância de doenças endêmicas em áreas urbanas: a interface entre mapas de setores censitários e indicadores de morbidade.

In this article we discuss the methodological issues associated with the creation of a surveillance system for endemic diseases in urban areas based on analysis of populations at risk and on spatially referenced epidemiological indicators. We comment on the system's basic requirements, selection criteria for socioeconomic variables, and methodological steps to combine these variables so as to construct a census-based deprivation index. We also present the ways we solved some operational problems related to generation of digitized census tracts maps and linkage of morbidity data from different sources. This approach, spatial organization into account in surveillance of endemic diseases, exemplified here by tuberculosis and leprosy, allows for the interaction of several official data sets from census and health services in order to geographically discriminate inner-city risk strata. Criteria for constructing these risk strata were considered a useful tool for health planning and management activities for the control of endemic diseases in cities.

The importance of operational factors for the interpretation of indicators in the Hansen's disease endemic in Brazil.

In Brazil, an increase has been recorded in recent years in the magnitude of detection coefficients for new cases of Hansen's disease, which is frequently interpreted as evidence of the endemic's expansion. The objective of this work is the determine the role of operational factors for interpreting the trend displayed by the morbidity coefficients for Hansen's disease from 1982 to 1995 in the country. We observed a strong correlation between the adjusted detection coefficients and the number of technicians trained (r = 0.80), a decrease in the proportion of new cases with disabilities at the time of diagnosis (r = 0.86), and a downward trend in tuberculoid forms (r = -0.70). Patient time on the active register is correlated negatively with MDT-WHO coverage (r = -0.95) and the percentage of patients discharged from treatment due to cure (r = -0.91). These results suggest that the increase in the potential for detection of new cases of Hansen's disease resulting from new strategies adopted by the program, i.e., mainly extensive training of health personnel, could be a coherent explanation for the increase in detection coefficients for new cases observed in Brazil in the last ten years.