Correlation between the zona-free hamster egg sperm penetration assay and human in vitro fertilization

The association between in vitro fertilization (IVF) and the zona-free hamster egg sperm penetration assay (SPA) was studied in 134 couples. The indications for IVF were tubal disease in 82 couples, unexplained infertility in 23, male infertility in 10, and combined mechanical and male factors in 19. In general, a positive SPA was a good predictor of subsequent IVF (91 of 107 couples). Specificity (number of couples with fertilization in vitro divided by the number of couples with a positive SPA times 100) was 94% for tubal infertility, 76% for unexplained infertility, and 46% for male infertility. A negative SPA predicted an overall fertilization failure of 78% (21 of 27 couples). Sensitivity of the test (number of couples with IVF failure divided by the number of couples with a negative SPA times 100) was 100% for tubal and unexplained infertility but only 63% for male infertility. The high predictive value of the SPA for subsequent IVF outcome in tubal infertility and unexplained infertility warrants its routine use for prescreening in IVF programs. Because of the lack of association between SPA and IVF in oligoasthenospermia, the bioassay should not be relied upon for predicting IVF outcome in male subfertility. The overall high association between the animal model and human IVF reinforces the use of the SPA for both basic research and clinical decision-making.