Clinical evaluation of the heterologous oocyte penetration (HOP) test

The heterologous oocyte penetration (HOP) test, using zona-free hamster oocytes, was used to assess the fertilising capacity of human spermatozoa. There was good correlation between the ability of ejaculated spermatozoa to penetrate the zona-free hamster oocytes and intact human oocytes. Using epididymal spermatozoa, the HOP test results showed that the ability to penetrate oocytes was acquired during their passage through the epididymis. Applied clinically, the HOP test enables a group of infertile men to be identified with a functional defect of their spermatozoa; these men may not be identified at routine seminal fluid analysis. Men with two negative HOP test results were confirmed as being infertile since their wives, if normal, conceived rapidly when donor spermatozoa were artificially inseminated.