IMPACT OF ANTIRETROVIRAL COMBINATION THERAPIES ON AIDS SURVEILLANCE REPORTS IN SWITZERLAND

Background: AIDS reporting in Switzerland is mandatory by law. For the first time since the beginning of the epidemic, health authorities ob served a decline in AIDS surveillance reports, from 545 new cases in 1 995 to 459 in 1996, a decrease of 86 cases. Objective: To examine the extent to which this decline in AIDS surveillance reports is attributa ble to the introduction of antiretroviral combination therapy. Patient s and setting: Swiss HIV Cohort Study, a multicentre cohort of adult H IV-infected patients with national overage. Participants at risk of de veloping a first AIDS-defining event, defined as persons with a CD4 ce ll count below 200 x 10(6)/l or in clinical stage B, were studied. Met hods: A parametric statistical survival model was used to estimate the number of AIDS cases expected in the absence of combination therapies . Taking reporting delays into account, the effect of the introduction of combination therapies in the cohort on national AIDS reports was e stimated from the difference between the number of expected and observ ed cases. Results: A total of 4915 participants contributed 10 755 per son-years and 2366 initial AIDS events. Between 1990 and 1994, about 3 5% received antiretroviral therapy, predominantly monotherapy. In 1995 and 1996, the prevalence of antiretroviral therapy increased steadily due to the introduction of dual and triple combinations. The mid-year prevalence of use of combination therapies was 6% in 1994, 13% in 199 5, and 48% in 1996. The difference between expected and observed cases per half-year increased from 12 in the first 6 months of 1994 to 69 i n the second half of 2996. Taking reporting delays into account, we es timated that 43 (95% confidence interval, 17-69) of the deficit of 86 reports could be attributed to combination therapies. Conclusion: The introduction of antiretroviral combination therapies in a single cohor t study explained 50% of the decline in national AIDS surveillance rep orts. Monitoring the use and effectiveness of antiretroviral therapy m ust become an important component of AIDS surveillance systems. (C) 19 98 Lippincott-Raven Publishers.