Data quality of dengue epidemiological surveillance in Belo Horizonte, Southeastern Brazil

Objective To evaluate the quality of data from the Brazilian information system for mandatory reporting diseases, for the detection of cases notified as suspected dengue fever and hospitalized in the public and private hospitals associated to the Public Health System. Methods The study was carried out in Belo Horizonte, Southeastern Brazil, during the years of 1996 to June 2002. The criterion of evaluation used were those recommended 4), the Guidelines for Evaluating Public Health Surveillance Systems. As a reference standard, medical charts recorded in the Unified System hospitalized discharge database system were revised and validated. A total of 266 (90%) of 294 medical charts were selected; 230 (86.5%) filled the suspect dengue fever criterion. To verify possible association between underreporting and selected variables, was used the odds ratio, with 95% of confidence interval in a logistic regression model. The sensitivity was defined as the proportion of hospitalized dengue cases registered in both systems. Predictive value positive was calculated as the proportion of confirmed cases and those recorded in the reporting system Results Underreporting of suspected dengue fever was of 37% cases during 1997 to 2002, it was five times higher during the first three years (OR=5.93: 95% CI: 2.50-14.04) and eight times higher for patients hospitalized it? private hospitals than in the public ones (OR=8.42; 95% CI: 2.26-31.27). Underreport was also associated to cases with no haemorrhagic episodes (OR=2.81: 95% CI: 1.28-6.15) and without dengue-specific laboratory exams in medical charts (OR=4.07; 95% CI:1.00-16.52). Sensitivity was 63% and predictive value positive was 43%. Conclusions Cases recorded in the reporting. system were those more severe and did not represent the total of cases hospitalized in Unfied Health System. thus the case fatality, rate may be overestimated The results indicate the necessity of changes in the evaluated surveillance model and in the implementation of the qualification of the health professionals, mainly those working in the private hospitals associated to Unified Health System.