Risk factors for HIV infection in adults attending sexually transmitted disease clinics in Italy

We assessed prevalence and risk factors for human immunodeficiency virus (HIV) infection in 637 patients (506 men, 131 women; median age 30 years, range 17-64) attending between September 1988 and July 1989 for the first time two sexually transmitted disease (STD) clinics in Northern Italy, for suspected or STD treatment. A total of 44 subjects (6.9%, 95% confidence interval, (Cl): 4.9-8.9) were seropositive for HIV antibodies. The prevalence of HIV infection decreased with age, from 9% in patients aged 24 years or less to 3% in those aged 45 years or more (chi 21 trend 4.97, p less than 0.05). Women tended to have a lower prevalence of infection than men (5.3% versus 7.3%) but this was not statistically significant. Compared with men reporting no homosexual intercourse, HIV infection risk was about 50% higher in those reporting bisexual intercourse (age- and sex-adjusted odds ratio (OR) 1.5,95% Cl: 0.6-3.6) and about fourfold in those reporting only homosexual intercourse (OR 3.8, 95% Cl: 1.7-8.5). No clear trend in risk was observed with number of sexual partners both in men and in women. Intravenous drug users had an increased risk of HIV infection; compared with non-users, the OR was 5.6 (95% Cl: 3.0-10.5) in users, and the point estimates increased with frequency of use, from 3.3 (95% Cl: 0.8-11.5) in occasional users to 6.4 (95% Cl: 3.2-12.8) in regular users. The risk of HIV infection was 2.2 (95% Cl: 1.1-4.3) in patients reporting a history of STD, and 1.6 (95% Cl: 0.8-3.3) in those reporting syphilis.(ABSTRACT TRUNCATED AT 250 WORDS)