2 FUNCTIONAL ASSAYS OF SPERM RESPONSIVENESS TO PROGESTERONE AND THEIRPREDICTIVE VALUES IN IN-VITRO FERTILIZATION

We have recently reported, in a small cohort of subjects, that acrosom e reaction (AR) and intracellular free calcium ([Ca2+](i)) increase in response to progesterone were significantly correlated with in-vitro fertilization (IVF) rate, In the present study we extended these resul ts to 90 subjects undergoing IVF. We confirm that both parameters were highly significantly correlated with the fertilization rate (P < 0.00 1), In particular, significantly lower responses to progesterone were detected in subjects with a fertilization rate <50%, further enlighten ing the functional significance of sperm responsiveness to progesteron e with respect to the process of fertilization, Moreover, we report he re that both tests are highly discriminant of fertilization success, w ith positive predictive values >90% for [Ca2+](i) values which increas e by >1.2-fold and AR inducibility >7% (cutoff values), Conversely, AR following challenge with the calcium ionophore A23187 was less signif icantly correlated with the percentage fertilization rate (P < 0.05), and showed lower predictive values than response to progesterone. All these tests ([Ca2+](i) increase in response to progesterone, AR in res ponse to progesterone and to A23187) appear highly sensitive and moder ately specific, The positive predictive value may rise to >95% when th e combination of two tests ([Ca2+](i) and inducibility of AR in respon se to progesterone) is considered, No correlation with fertilization r ate has been found for spontaneous AR or basal [Ca2+](i). In conclusio n, we propose that assessment of human sperm responsiveness to progest erone may be clinically useful in predicting fertilizing ability in vi tro.