COMBINING HIV AND AIDS SURVEILLANCE - AN EXPERIENCE FROM AN ITALIAN REGION

Background. Surveillance systems based on the reporting of AIDS cases do not provide a completely up to date picture of the trend of the HIV epidemic, stressing the need for systems based on the diagnosis of HI V infection. However, implementation of these systems has been hindere d by low feasibility, poor access to HIV testing, and problems related to confidentiality. The advantages and disadvantages of the two syste ms and of combined use were explored by comparing and integrating info rmation from AIDS and HIV testing registries in a region of Northern I taly. Methods. Linkage of AIDS and HIV testing registries allowed the annual number of incident and prevalent infections to be calculated. F or linked cases, concordance of exposure category was determined. Resu lts. Up to the end of 1995, 2186 AIDS cases and 5306 HIV-positive indi viduals were diagnosed. Linkage identified 1212 individuals reported t o both registries. From 1990 to 1995, annual AIDS incidence steadily i ncreased, while incidence of new HIV diagnoses decreased. The AIDS-to- AIDS-free ratio among those infected decreased from 1:5.6 in 1989 to 1 :4.2 in 1995. The proportion of women and noninjecting drug users was higher among AIDS-free cases than among AIDS cases. The concordance of the exposure category was high (K = 0.70; 95% CI : 0.67-0.74), but it varied by exposure category; the highest concordance was for injectin g drug users. Conclusions. Integrated use of the information provided by these surveillance systems allowed us to better understand and fore see the AIDS epidemic dynamics. The data also suggested that the relia bility of information on exposure category may vary among categories.