sperm immobilization test, (for male factor infertility) a test for antisperm antibodies as a cause of infertility, based on the loss of ability of spermatozoa with such surface antibodies to move when complement is present (as it normally is in the female reproductive tract). Serum from the patient is incubated with motile sperm and complement is added. After 1 hour the mixture is checked to calculate the percentage of formerly motile sperm that can no longer move; a 50% reduction in motility is a positive result for presence of antisperm antibodies. Also called Isojima test.
