Immunoglobulins on human sperm: validation of a screening test for sperm autoimmunity.

The immunobead test (IBT) is a new method of detecting antisperm antibodies with the advantages of enabling determination of the presence of antisperm antibodies during routine semen analysis, immunoglobulin isotypes and antibody specificity for binding to sperm structures such as head or tail. The IBT is compared with the conventional methods of detecting antisperm antibodies in serum; the tray agglutination test (TAT) and the sperm immobilization test (SIT). Positive IBT (50% or more of washed motile sperm binding to anti-IgG and/or anti-IgA immunobeads) were found in 6.8% of 689 men being investigated for infertility. Both IgG and IgA were found to be present in all cases. The IBT correlated closely with the serum antisperm antibody tests; of the 202 men tested by all three methods, 200 (99%) were either positive for circulating antibodies and IBT or negative for both. No men with serum antisperm antibodies lacked local antisperm antibodies as detected by IBT, and only two men (1%) were IBT positive in the absence of either one or both types of circulating antibodies. Individually, the TAT and the SIT correlated equally well with the IBT; 97% and 98% of men tested by TAT and IBT, and SIT and IBT respectively, were either positive by both or negative by both. It is concluded that the IBT is an excellent procedure for the detection of sperm antibodies.