COMPARISON OF THE IMMUNOBEAD BINDING TEST (IBT) AND IMMUNOSPHERES (IS) ASSAY FOR DETECTING SERUM ANTISPERM ANTIBODIES

PROBLEM: The IBT is considered the gold standard of sperm antibody ass ays. This test uses polyacrylamide beads labeled with antiglobulins (a nti-IgG, anti-IgA, and anti-IgM), which bind to the corresponding anti body on the sperm surface. The IS uses color-coded latex beads of unif orm 3.0 mu m size coated with the antiglobulins which can be viewed wi th brightfield light microscopy. The purpose of the present study was to compare the IBT and IS in an indirect test using human serum. METHO D: Serum specimens (n=42) were tested for the presence of antibody iso types IgG, IgA, and IgM to sperm using the standard protocol for IBT a nd IS. Donor sperm was washed in BWW with 5% BSA and diluted to a fina l concentration of 50 x 10(6) motile sperm/ml. The sperm were incubate d with a 1:10 dilution of test serum for 30 min to 1 h at 37 degrees C and then washed by three cycles of centrifugation. The sperm and bead s (IBT, IS) were mixed on a glass slide, covered with a coverslip, and observed within 5 min. At least 100 motile sperm were counted and sco red for bead binding. A specimen was considered positive if 20% or mor e of the sperm were coated with one or more beads. The data were analy zed using calculation of the non-parametric kappa statistic with corre ction for chance expected agreement, and by calculating the proportion of specific agreement between the two methods. RESULTS: The results a re summarized in the following table: [GRAPHICS] The IS was able to de tect 94% of IgG antibodies, 91% of IgA antibodies, and 100% of Ig M an tibodies. One serum specimen was IgG negative by IS (14% binding), but positive by IBT (20%). A second serum specimen was IgA negative by IS (16%) yet positive by IBT (29%). There were no false positives with t he IS assay. Of the IgM positives (five of six) occurred alone and not with IgG or IgA, suggesting the necessity for testing all specimens a lso for IgM. CONCLUSION: Antisperm antibody test results obtained by t he IS assay are in agreement with the results obtained with the IBT te st. The Immunospheres are monodispersed, color coded, and can be visua lized with brightfield microscopy.