The Sperm Penetration Assay as a Screening Tool for Assisted Reproduction.
Straub RJ, Massey JB, Mitchell-Leef DE, Toledo AA, Keenan DL, Roudebush WE. Reproductive Biology Associates, Atlanta, GA.
Objective: Achieving pregnancy in the infertile couple can be challenging and frustrating for the couple. Ideally, as successful pregnancy would be established in the shortest amount of time while being minimally invasive and containing cost. Many patients undergo multiple failed cycles of controlled ovarian hyperstimulation (COH) and intrauterine insemination (IUI) prior to attempting IVF-ET. We focused on the sperm penetration assay (SPA) as a potential screeing tool to aid in the decision making process of whether to forego COH-IUI cycles in favor of IVF-ET. Our study objective was to determine the predictive value of the SPA with pregnancy rates in our IUI program.
Design: Comparison of SPA scores with IUI outcomes.
Materials and Methods: SPA scores (number of penetrations/number of zona-free hamster ova) were prior to IUI. Sperm for the SPA incubated in test yolk buffer for 48-72 hours at 4oC to induce capacitation. Zona-free hamster ova were inseminated with 300,000 motile sperm and co-incubated in modified HTF at 37oC for 3.5 hours. Ova were washed free of bound non-penetrated sperm cells and evaluated for penetrations. Semen specimens for IUI were processed through a 90% density silane coated silica suspension, washed with 4mL of sperm wash, and resuspended with 0.5mL of PureSperm Wash. Positive clinical pregnancy was confirmed with a positive heartbeat on ultrasound.
Results: Pregnant patients had a mean (+SEM) SPA of 6.52 (+1.58), where non-pregnant patients had a mean (+SEM) SPA score of 4.94 (+1.45). A receiver-operator characteristic (ROC) curve was calculated to determine what SPA score best predicted a positive pregnancy outcome. The ROC curve indicated a SPA cutoff score of 3 (sensitivity, 0.83; specificity, 0.50; diagnostic accuracy, 0.64; positive predictor, 0.56; negative predictor 0.80). With this criterion, patients that passed the SPA had a pregnancy rate of 56%, patients that failed the SPA had a pregnancy rate of 20%.
Conclusion: Incorporating the SPA into the diagnostic work-up may facilitate the decision making process for the physician as well as the couple. In our laboratory, we found that the SPA score cut-off for a successful pregnancy following IUI is 3. Those couples that failed to reach the cutoff had a markedly lower pregnancy rate. In these situations, counseling patients to consider IVF-ET as the primary treatment may be an option. Fast tracking to IVF-ET for a particular couple with a poor SPA would offer a greater chance of pregnancy while reducing overall treatment cost and shortening the duration of treatment.