I was a steady ARC donor for 15 years ending ~1995. The med-techs had developed a blood test for HIV by the mid-1980s, and it has supposedly been improved since then. The joke back then was that those people who were at risk for contracting HIV could go donate blood at the ARC and get a free HIV test at the same time.
By 1995 the ARC had already implemented a long questionnaire for prospective donors to serve as a self-report screening tool. I have searched the ARC sites as recently as 1 year ago and could find no mention of what the exact testing policy was for HIV or other disease agents in donated blood.
My impression is that the biggest blood donor agencies in the U.S. are the ARC, AHA, and blood centers sponsored by hospitals.
see #67