Reduced frequency of blood donors with false-positive HIV-1 and -2 antibody EIA reactivity after elution of low-affinity nonspecific natural antibodies.

BACKGROUND

The detection by EIA of antibodies (Abs) specific to HIV antigens in the serum of blood donors is important for transfusion safety. A small but significant number of donor sera (0.1-0.3%) yield false-positive results in EIA, and these donors must be permanently deferred from the blood donor list, causing operational and public relations problems.

STUDY DESIGN AND

METHODS

False-positive EIA reactions could be caused by the binding of low-affinity natural polyreactive Abs, which could be eluted by treatment with a chaotropic agent such as thiocyanate (SCN). The effect of the SCN elution on EIA specificity was studied using tetanus toxoid and HIV Abs.

RESULTS

SCN elution preferentially reduced the binding of nonspecific Abs. Testing of 235 seronegative samples in HIV-1 and -2 EIA showed that SCN elution reduced the mean and dispersion of OD values obtained. In addition, SCN elution abolished the false-positive reactivity in HIV-1 and -2 EIA of 69 percent (299/435) of the repeatedly reactive specimens tested without impact on the reactivity of HIV-seropositive specimens.

CONCLUSION

The SCN elution step increased the specificity of HIV-1 and -2 EIA and could facilitate the re-entry of previously deferred donors.