An immunosorption assay for antibodies to spermatozoa: comparison with agglutination and immobilization tests.

We have developed an enzyme-linked immunosorption assay (ELISA) with an antigen extract made by treatment of freeze-thawed sperm pools with 0.3 M lithium 3,5-diiodosalicylate (LIS). This procedure is quick, safe, and simple to perform in a clinical laboratory. When the LIS antigen preparation was compared by ELISA with whole sperm and several other antigen extracts, it was found to be superior in detecting human antisperm antibodies related to infertility; it gave less variability, better precision, and fewer false-positive reactions than whole sperm fixed to the wells as antigen. The antigen was stable when stored at -20 degrees C. In one experimental series, serum samples from 18 normal control subjects and 159 infertility patients with positive sperm-immobilizing titers, positive sperm-agglutinating titers, or both, were tested by ELISA with LIS antigen; the correlation yielded a P less than or equal to 0.0001. Based on another series of 156 samples from patients with positive antibody titers by the sperm agglutination test and 30 sera from normal humans, the predictive value of the test was 96%. In a third series of 162 serum samples obtained from 82 women and 80 men, we found no difference in the test results based on sex. The assay is specific for the antibody binding portion of the immunoglobulin. Absorption of positive sera with sperm but not red blood cells markedly reduces the response. In addition to being more efficient and precise than standard methods, the ELISA eliminates the need for fresh sperm and provides data that can be objectively interpreted.