Objectives: This paper describes the rationale and design features of the Swiss HIV Cohort Study (SHCS) and the baseline characteristics of participants enrolled up to March 31st 1993. The objectives include epidemiological, clinical and laboratory research.
Design: The SHCS is a prospective cohort study of HIV infected adolescents and adults seen at the outpatient clinics of the Swiss University Hospitals in Basle, Berne, Geneva, Lausanne and Zurich and the Cantonal Hospital St. Gall. The multicentre collaboration was initiated in September 1988 by the Swiss Federal Office of Public Health. Data collected prior to this date by several participating centers using a similar protocol were included, the earliest records dating back to 1982. Follow-up visits are scheduled every 6 months.
Enrollment: As of March 31st 1993, 6253 participants (M: 4580, F: 1675) were included with a total of 16015 person-years of follow-up (mean 2.6 years). HIV transmission categories were 46% intravenous drug users (IDU), 32% men who had sex with men (MSM), 18% heterosexual contacts (HET) and 4% other. The proportion of MSM among male participants decreased from 62% in 1985 to 40% in 1987, to remain stable thereafter. The proportion of IDU among males was around 40% throughout, whereas in females, there was a pronounced decline from 90% IDU in 1985 to 50% in 1992. Conversely, there was a striking increase in registrations of women presumably infected by HET, from 8% in 1985 to 50% in 1992. Among men, the proportion classified as HET increased from 2% to 15%. It is estimated, that a large proportion of all Swiss AIDS patients (70%) and HIV infected individuals (32%-47%) are enrolled in the Swiss HIV Cohort Study. Losses to follow-up, however, are common.
Conclusions: The SHCS serves multiple purposes as a research project, as infrastructure for multidisciplinary research and as a tool to improve patient care. Several international and national trials, post-marketing surveillances and expanded access protocols were or still are based upon its infrastructure. The large number of female participants and of participants AIDS-free at entry, make the database especially valuable.