[The extent of transfusion-associated HIV infections in Switzerland until 1994: an updated estimate]

The first report on transfusion-associated HIV infections was published in the USA in 1982. The first case reports in Switzerland were published in 1986. So far there has never been a methodologically sound answer to the question of how many persons were infected with HIV by receiving transfusions in Switzerland before the introduction of universal HIV blood donor screening.

The following available data sources were analyzed simultaneously: firstly, the results of the look-back study conducted in 1993, secondly, the reports of HIV infections and AIDS cases in the national surveillance system, and, thirdly, the claims for compensation for HIV-infected transfusion recipients and hemophiliacs. Two methodologically different and independent estimates were obtained. Firstly, the coverage of the look-back study was estimated, which made it possible to calculate the total number of documentable transfusion-associated HIV infections in Switzerland. Secondly, matching was performed on the cases in the look-back study and the reports in the national surveillance system. Applying formulas of capture-recapture designs provided a second estimate of the total number of documentable transfusion-associated HIV infections. The claims for compensation were used to corroborate the estimates obtained.

The two methods produced almost identical figures which were corroborated by the number of claims for compensation. It is therefore estimated that 80 to 100 persons in Switzerland may have been diagnosed as having HIV infection because of transfusions in Switzerland in the years after 1980. The last five known infections occurred in 1986 (four) and, after termination of the look-back study, in 1994 (one). However, the estimate of 80 to 100 does not include individuals who were infected before 1986 and died soon--within weeks or a few months--after the transfusion without diagnosis of HIV infection being possible.

This estimate of the total number of transfusion-associated HIV infections in Switzerland is approximately half earlier published ones. In addition, the present study will probably reduce the remaining uncertainties about the size of these iatrogenic HIV infections in the 1980s.