Estimated rate of HIV-1-infectious but seronegative blood donations in Bangkok, Thailand.

OBJECTIVES

To determine HIV seroprevalence and incidence among various blood donor types, and to estimate the rate of window-period blood donations.

DESIGN

Retrospective cohort from computerized donor records.

METHODS

Records were analysed from all 60,483 donors (contributing 97,464 donor units) at a public university teaching hospital blood bank in Bangkok, Thailand, from 1 January 1990 to 30 June 1993. Annual HIV incidence among 14,482 repeat donors who were HIV-seronegative on their first donation was calculated assuming equal probability of seroconversion between last seronegative and first seropositive donations. To estimate the probability of window-period donations, we assumed that the time from HIV infectivity to onset of detectable antibody was 45 days.

RESULTS

In 1990, HIV incidence calculated for all repeat donors was 307 per 100,000 person-years; the probability of a window-period donation was 38 in 100,000 donations or one in 2644 donations. During 1991-1993, this probability decreased by one-half. However, one-time donors were more than twice as likely as repeat donors to be HIV-1-seropositive.

CONCLUSIONS

The rate of HIV window-period blood donations among Thai repeat donors was relatively high compared with that in developed countries and was probably even higher among one-time donors. Improved donor deferral criteria are needed in Thailand.