The effects of different sperm preparation methods and incubation time on sperm DNA fragmentation

Purpose: To study the effect of different sperm preparation methods and incubation times post preparation on sperm DNA fragmentation. Methods: Sperm DNA fragmentation was assessed by the sperm chromatin dispersion (SCD) method on motile sperm prepared by gradient centrifugation or swim-up and incubated in IVF medium for up to 24 hours. Data were analyzed to discover the effect of preparation methods and incubation times on the sperm DNA Fragmentation Index (DFI). Results: There were no differences in DFI in sperm samples prepared by a gradient centrifuguation method or swim-up (3.87 +/- 2.14 vs. 3.45 +/- 1.83, p = 0.544). However, an increase was observed in DFI in samples prepared by swim-up after 6-8 hours compared with by gradient centrifugation (34 degrees vs. 13 degrees, p = 0.04). In the swim-up group, the DFI level at 4 hours was already significantly higher than it was initially. However, following gradient centrifugation, the DFI at 8 hours was significantly higher than the initial DFI level. Conclusion: Sperm samples prepared by gradient centrifugation may be more stable, in terms of DNA fragmentation, than samples prepared by swim-up.