An immunoglobulin G antibody capture particle-adherence test (GACPAT) for antibody to HIV-1 and HTLV-I that allows economical large-scale screening.

GACPAT is a modification of a gelatin particle-agglutination test for the detection of anti-HIV-1 and anti-HTLV-I. In it, antigen-coated particles react with immunoglobulin captured from the specimens onto the surface of U-bottomed reaction wells previously coated with anti-gamma chains. In initial tests on 1127 blood donations, of 628 HIV-1 high-risk specimens and 176 HTLV-I high-risk specimens, GACPAT for anti-HIV-1 was 98.9% specific and 100% sensitive, and for anti-HTLV-I was 99.0% specific and 93.0% sensitive. It rivalled the sensitivity of second-generation enzyme-linked immunosorbent assays (ELISA) for anti-HIV-1 in tests on specimen dilutions and on seroconversion series. GACPAT can be used as a cheap, large-scale test and as a simple confirmatory check on other assays.