Comparison of a Direct and Indirect ELISA for Quantitating Antisperm Antibody in Semen

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Abstract
A direct and an indirect quantitative ELISA for antisperm antibody were compared using the spermatozoa and cellfree seminal fluid of 66 infertile males. The normal concentration of sperm binding immunoglobulin was ≤ 1.5 fg Ig per spermatozoon for the indirect seminal plasma assay and ≤ 1.5 fg Ig per spermatozoon by the direct assay. Of the 66 infertile males, 21% (14/66) had elevated levels of antisperm antibody in their seminal plasma and 26% (17/66) had elevated levels bound directly to their spermatozoa. The direct correlation between the results of these assays was 94%. A simple linear regression analysis between the indirect and direct measurements of antisperm antibody resulted in a correlation coefficient of r=0.907. There was no statistically significant difference between results from the direct and indirect methods of the patients as a group. However, there was evidence of autospecificity in a small percentage of males who had elevated levels of antisperm antibody by the direct assay that was not detected by the indirect assay using pooled donor spermatozoa.