Background: A major epidemic of human immunodeficiency virus type 1 (HIV-1) infections that are primarily due to heterosexual transmission has developed in Thailand since 1988. The epidemic has been most severe in northern Thailand. The blood banks in Chiang Mai began screening donors for HIV-1 antibodies in February 1988 and for p24 antigen in April 1992.
Study design and methods: The trends of HIV-1 antibody prevalence were analyzed by type of donor (i.e., paid, replacement, and voluntary) for the period of 1988 through 1993. In addition, the prevalence of HIV-1 p24 antigen and of antibodies to syphilis, hepatitis B surface antigen, and hepatitis C virus was evaluated among blood donors at Chiang Mai University Hospital and the Thai Red Cross blood banks in Chiang Mai.
Results: The prevalence of HIV-1 antibodies increased from 0.84 percent in 1988 to 4.04 percent in 1991. Seropositivity was highest in paid professional donors. After discontinuation of the use of paid donors in 1993, HIV-1 antibody prevalence decreased to 3.34 percent. Antibody prevalence in replacement donors increased from 0.56 percent in 1988 to 5.82 percent in 1991. Among 44,446 donors tested, 7 (0.016%) were HIV-1 p24 antigen positive but antibody negative.
Conclusion: The exclusion of paid donors and the use of p24 antigen testing are justified in northern Thailand. Additional strategies to exclude donors at very high risk and to attract those at low risk for infection should be developed and evaluated to increase blood transfusion safety in this and other, similar populations.
PIP: A major epidemic of human immunodeficiency virus type 1 (HIV-1) infections has developed in Thailand since 1988. The blood banks in Chiang Mai began screening donors for HIV-1 antibodies in February 1988 and for p24 antigen in April 1992. The trends of HIV-1 antibody prevalence were analyzed by type of donor (i.e., paid, replacement, and voluntary) for the period of 1988 through 1993. In addition, the prevalence of HIV-1 p24 antigen and of antibodies to syphilis, hepatitis B surface antigen, and hepatitis C virus was evaluated among blood donors at Chiang Mai University Hospital and the Thai Red Cross blood banks in Chiang Mai. The prevalence of HIV-1 antibodies in donor sera increased from 0.84% in 1988 to 3.23% in 1989. It continued to increase in subsequent years, reaching a maximum of 4.04% in 1991; the prevalence declined slightly in 1992 and 1993. In the first year of screening, the prevalence of HIV antibodies was highest in paid professional donors. The use of paid donors was discontinued on July 1, 1992, largely because of their high rates of HIV seropositivity. This action lowered the prevalence of HIV infection in the overall donor population in 1992 to 3.61%, from the peak of 4.04% in 1991. Antibody prevalence in replacement donors increased from 0.56% in 1988 to 5.82% in 1991. Screening for p24 antigen, introduced on April 29, 1992, identified 48 infected donors (among the 44,446 donors tested in 1992 and 1993) who were HIV p24 antigen positive. Altogether, 7 (0.016%) donors tested repeatedly reactive for p24 antigen, had positive p24 antigen neutralization tests, and were negative for antibodies to HIV. The exclusion of paid donors and the use of p24 antigen testing are justified in northern Thailand. Additional strategies to exclude donors at very high risk and to attract those at low risk for infection should be developed.