Serum inhibin B cannot predict testicular sperm retrieval in patients with non-obstructive azoospermia

BACKGROUND: Serum inhibin B, a direct product of the Sertoli cells, may serve as a marker of spermatogenesis. The present retrospective study aimed at evaluating the predictive value of inhibin B for retrieving testicular sperm in non-obstructive azoospermic men. METHODS: The serum inhibin B concentration before sperm retrieval was reviewed in 185 non-obstructive azoospermic patients. RESULTS: Testicular sperm were successfully recovered in 92 of 185 patients (49.7%). The mean inhibin B concentration in these patients was 37.3 pg/ml. No sperm were found in 93 patients (50.3%), and the mean serum inhibin B concentration was 44.9 pg/ml. The discrimination between successful and unsuccessful sperm retrieval was analysed using the receiver operating characteristics (ROC) curve analysis. The best discriminating inhibin B concentration was 13.7 pg/ml (sensitivity 44.6%, specificity 63.4%) with an area under the ROC curve (AUC) of 0.51. Combining both serum FSH and inhibin B did not improve the predictive value: the AUC of inhibin B in men with a serum FSH concentration <25 and ≥25 IU/l (being the best threshold value in the population studied) was respectively 0.53 and 0.50. The AUC of the inhibin B:FSH ratios was 0.55. CONCLUSIONS: This analysis shows that inhibin B, either alone or in combination with serum FSH, fails to predict the presence of sperm in men with non-obstructive azoospermia undergoing testicular sperm extraction.