Anti-sperm antibodies, detected by agglutination, immobilization, microcytotoxicity and immunobead-binding assays. 
To determine the reliability of tests currently utilized in the detection of sperm-reactive antibodies, sera were provided as unknowns and studied without knowledge of the clinical histories.  Four laboratories performed tray agglutination tests (TAT), three complement-dependent immobilization (SIT), and single laboratories sperm cytotoxicity (SCT), passive haemagglutination (PHA) and immunobead binding (IBB).  Most investigators demonstrated an excellent correlation between duplicate sample results.  Nearly all of the female sera were free of anti-sperm antibodies and positive results did not appear in greater frequency in women with unexplained infertility as compared with other categories.  For the male sera, the highest incidence of anti-sperm antibodies in the infertile group (21% positive for sperm-reactive IgGs) was obtained by immunobead binding.  The GAT and TAT results gave 7 and 12% positives, except for lower results in one laboratory.  Sperm-reactive antibodies were detected most commonly in vasectomized men, with all assays except SCT and PHA.  Of the newer techniques studied, IBB results correlated well with TAT, GAT and SIT, while SCT and PHA did not, suggesting that a different group of antibodies, perhaps directed against other sperm-associated antigens, was being detected by the latter procedures.  In this light, emphasis was placed on the need to validate whether results of particular methodologies correlated with impaired sperm function and to develop methods that provided evidence for this premise, either on the basis of clinical criteria or altered gamete interaction in vitro.