[Mandatory anonymous HIV-surveillance in Denmark. Experience with the new notification system]

A newly implemented mandatory, anonymous HIV surveillance system in Denmark is described. The system is based on a serially numbered form that is circulated among the laboratories, the physicians, and the national surveillance unit. All laboratories doing confirmatory tests for HIV antibodies must send a report form along with any positive test result. Before forwarding the form to the physician, the laboratory is to fill in the top part of the form with its own name, the name and address of the requesting physician and the date of testing. The back copy must be send to the surveillance unit. The Danish physicians are by law mandated to fill in the form with data on the patient and then send the original to the surveillance unit. The two copies are for the patient's file and for the physicians' own centralized filing system. After a revision of the system in 1992, a response rate of 95% was obtained during the first year. An increasing number and proportion of first-time identified HIV-infections in Denmark are acquired heterosexually, many of these infections are identified among foreigners. The newly developed mandatory HIV surveillance system is based on anonymous reporting but it allows routine evaluation of the completeness of reporting as well as nonresponding physicians to be reminded of their duty to report. Also, the system allows nested studies to be carried out among selected HIV-infected subpopulations of special research interest without compromising the anonymity of the patient.