Anti-HTLV III ELISA and Western blot testing in a blood donor population: implications for donor notification.

We have evaluated the western blot (WB) test for distinguishing anti-HTLV III ELISA-positive donors who have likely been exposed to HTLV III from those that are false positives. Of 1,955 donors, 26 were positive for anti-HTLV III by ELISA testing. Only 6 (23%) were positive by WB: 5 of these 6 were male homosexuals with multiple partners and 5 of 6 had low Th/Ts ratios. The WB-positive donors gave the highest absorbance values in the anti-HTLV III ELISA assay. The immunologic abnormalities in the WB-positive donors suggest that they should be notified of their test results. We conclude that basing a donor notification policy on WB results is the optimum public health strategy for blood banks at the present time.