POTENTIAL DEFERRAL CRITERIA PREDICTIVE OF HUMAN-IMMUNODEFICIENCY-VIRUS POSITIVITY AMONG BLOOD-DONORS IN THAILAND

Background: To develop deferral criteria to prevent human immunodeficiency virus (HIV) transmission by recently infected blood donors in the seronegative ''window'' phase, routine data on donors at a university hospital were examined for factors predicting seropositivity. Study Design and Methods: Records of all 281 HIV-positive blood donors from August 1987 through September 1991 were retrospectively compared with those of 1076 randomly selected control donors matched only by year of donation. Four controls were selected for each HIV-positive donor Results: The prevalence of HIV in 102,684 donor units during the period rose from 0.02 percent in 1987 to 0.52 percent in 1991. Multivariable analysts revealed that male sex (odds ratio [OR] = 26.4), VDRL test positivity (OR = 3.0), age 21 to 30 years (OR = 2.2; referent: 16-20-year-old group), and replacement donorship (OR = 1.4; referent: voluntary donors) were independent factors significantly associated with HIV positivity among these donors (p<0.05). Since replacement donorship cannot be avoided, only male sex, age 21 to 30 years, and VDRL test positivity were considered as potential criteria. When these findings were extrapolated to all donors in 1990 and 1991, those with all three or only two (excluding VDRL test, because the results are known only after donation) of these high-risk factors had HIV positivity probabilities of 2.2 and 1.0 percent, respectively. These probabilities were, respectively, 4.9 times (95% CI: 2.9, 8.3) and 4.1 times (3.1, 5.4) the risk among other donors. However, applying such criteria would have eliminated 1.5 and 31.2 percent, respectively, of all HIV-negative donors in 1990 and 1991. The latter deferral proportion is too high to be acceptable. Conclusion: In Thailand, improved donor deferral criteria addressing sexual risk factors could lead to decreased probability of window-period donation, with an acceptable rate of deferral. Additional p24 antigen testing may be indicated for donors at increased risk for HIV infection, specifically, men aged 21 to 30.