Explaining the Unexplained: Examining the Predictive Value of Semen Parameters, Sperm DNA Fragmentation and Metal Levels in Unexplained Infertility

Background: There is ongoing research to find an optimum modality to predict male fertility potential. Aims: To compare the semen parameters, sperm DNA damage and seminal metal levels of Zinc, Lead and Aluminium among the male partners of couples with unexplained infertility and men with proven fertility. Settings and Design: Prospective case-control study at a tertiary level teaching hospital. Materials and Methods: One hundred male partners of couples with unexplained subfertility and 50 men with proven fertility were included in the study. Male partners of unexplained infertility couples and fertile men were compared for their semen parameters, sperm DNA Fragmentation Index (DFI) and seminal metal levels in semen. Statistical Analysis Used: Chi-square test, Student's t-test, sensitivity and specificity analysis, binomial logistic regression analysis. Results: Fertile men had statistically significantly higher mean progressive sperm motility than male partners of unexplained infertility (53.12 +/- 9.89% vs. 44.81 +/- 19.47%, P = 0.005). Semen volume and sperm concentration were comparable among the cases and control population. The mean sperm DFI was significantly lower among fertile men (10.83 +/- 6.28 vs. 21.38 +/- 10.28, P < 0.0001). Plotting the receiver-operating characteristic curve the threshold for discrimination was calculated to be 18% DFI. The sensitivity specificity and overall accuracy were 43%, 84% and 56.67%, respectively when the DFI cut-off was set at 18%. Zinc concentration in the semen had a strong positive correlation (Point Biserial correlation coefficient = 0.831) with fertility, whereas lead and aluminium had a moderate negative correlation. Conclusion: Conventional semen analysis had limited differentiating ability for unexplained infertility. The sperm DFI may be employed for explanatory purposes among couples with unexplained subfertility. A lower discriminatory threshold of DFI (18%) has better overall accuracy as opposed to a 30% cutpoint for unexplained subfertility. Among metals, Zinc was strongly correlated with fertility status.