HIV incidence among repeat HIV testers with sexually transmitted diseases in Italy. STD Surveillance Working Group

To provide data on the incidence of HIV infection among repeat testers with sexually transmitted diseases (STD) in Italy.

Retrospective longitudinal study.

Study participants, enrolled by 47 STD centres throughout Italy, included individuals with a newly diagnosed STD who were tested for HIV at the time of the STD diagnosis and who had a previous documented HIV-negative test. 'Seroconverters' were defined as those individuals who tested HIV-positive at the time of the STD diagnosis. The cumulative and the annual incidence of HIV in this population were estimated.

Of 1950 patients, 47 were seroconverters, with an incidence rate of 1.7 per 100 person-years (PY) (95% confidence interval, 1.2-2.2). HIV incidence was higher among males than among females (2.5 versus 0.6 per 100 PY). The highest incidence rate was found among homosexual injecting drug users (IDU) (13.8 per 100 PY), whereas the lowest rate was observed among heterosexual non-IDU (0.4 per 100 PY). The annual incidence decreased from 1.8 per 100 PY in 1989 to 0.9 per 100 PY in 1996.

Our results show that new HIV infections have occurred among STD patients in Italy since 1988, although a clear decrease in incidence has occurred since 1989. However, the rate of seroconversion appears to be alarmingly high in some high-risk groups. These findings suggest that there is a need for continued monitoring of new HIV infections among STD patients, and these individuals may represent a useful sentinel population for a better understanding of the HIV epidemic.