Comparison of latex and polyacrylamide beads for detecting sperm antibodies

The immunobead test is excellent for the routine screening of semen for sperm antibodies but the polyacrylamide beads currently used are of variable diameter (3-10 micron) which tends to obscure details of regional binding. Thus the use of smaller latex beads of more uniform diameter has been investigated. Latex beads were coated with IgG by exposure to anti D serum for a mixed antiglobulin reaction (MAR). Rabbit antihuman IgG and IgA antibodies were covalently bound to carboxylated latex microspheres (CLM) by the carbodiimide reaction. Polyacrylamide immunobeads (IBT) with antihuman IgG or IgA antibodies covalently attached were obtained commercially. The IgG IBT and MAR were compared in 55 samples. The MAR was positive in 15 of the 31 IBT positive samples but the proportion of sperm with attached beads was lower. CLM and IBT were compared in 106 samples. Both tests were positive in 34 samples with virtually identical proportions of motile sperm with beads attached and the patterns of attachment were similar. These results show that CLM microspheres give equivalent results to IBT and that as they are smaller and have a more uniform size they provide advantage in ease of detection of positive reactions and in determination of the regional blinding pattern.