Sperm DNA fragmentation in subfertile men: the effect on the outcome of intracytoplasmic sperm injection and correlation with sperm variables

OBJECTIVE To present the first UK data on sperm DNA fragmentation levels in subfertile men and fertile controls, the correlation with semen variables, and to assess the effect on the outcome of intracytoplasmic sperm injection (ICSI). PATIENTS, SUBJECTS AND METHODS In all, 56 subfertile men undergoing ICSI (28 with positive and 28 with a negative outcome for paternity) and 10 control fertile semen donors were recruited. The sperm DNA fragmentation index (DFI) was assessed on raw pre‐preparation samples using the sperm chromatin structure assay. A mean of 5212 sperm were analysed per sample and DFI data are presented by fertility status, ICSI outcome and correlated with semen variables (assessed using World Health Organisation criteria). RESULTS Total DFI was significantly higher in subfertile men than in fertile controls (mean and median of 22.8% and 17.0% vs 8.4% and 5.0%; P  < 0.001), as was the proportion of both moderate DFI (16.4% and 13.0% vs 6.4% and 4.0%; P  = 0.001) and high DFI (6.2% and 6.1 vs 2.0% and 1.0%; P  = 0.01). This difference remained significant when the control men were compared only with the subfertile men with successful paternity. There was no significant difference in DFI in the subfertile men when analysed by ICSI outcome (mean and median of 24.5% and 17.0% vs 22.3% and 21.0% for successful and unsuccessful cycles, respectively; P  = 0.94). There was a positive statistically significant correlation ( r  = 0.37; P  = 0.02) between the DFI and sperm morphology. CONCLUSIONS This study confirms a relationship between male subfertility and sperm DFI; we discuss the correct role for genetic testing of sperm in the evaluation of subfertile men. Although DNA fragmentation data might help to decide a suitable treatment, once it is decided to proceed with ICSI, DFI levels have no effect on the outcome.