[HIV in Mexican blood donors and estimated transfusional risk]

To determine the HIV seroprevalence in Mexican blood donors and the residual risk of transfusion.

The seroprevalence was determined in a sample of first-time blood donors at one hospital center in Mexico City, from 2003 to 2007. To estimate the seroprevalence reported in Mexican blood donors, we reviewed recent papers. To determine the positive likelihood ratio (LR+) of the EIA test the specificity was calculated against the western-blot result. To infer the residual risk, the incident infections were assumed to be 1.8 times more frequent for first-time donors.

We analyzed 29,318 donors; 66 were reactive to HIV by EIA (225/100,000; 95% Confidence Interval: 171 to 279/100,000), but western-blot confirmed only 5 (prevalence = 17/100,000 donors; 95% CI: 2 to 32/100,000). The maximal residual risk was inferred to be 6.2 per million, or about 6.8 per year. The LR+ of the EIA test was calculated to be 476. The Bayesian analysis estimated that the disease is present in only 7.5% donors with a reactive EIA. Published reports in medical literature do not inform confirmatory tests for Mexican donors.

The residual risk for HIV had been calculated to be about 100 per million of blood donors. Although we inferred that the risk had been overestimated by not performing confirmatory tests, the results are a call for action as the risk is still several times higher than the one reported in industrialized countries.