The pellet swim-up is the best technique for sperm preparation during in vitro fertilization procedures

The aim of this study was to investigate the most suitable sperm preparation technique to apply in order to obtain a spermatozoon population with minimal DNA damage during in vitro fertilization procedures. We compared four preparation techniques: direct swim-up (DSU), pellet swim-up (PSU), density gradient (DG), and density gradient followed by swim-up (DG-SU), evaluating the effects of each technique on the DNA damage rate, evaluated by DNA fragmentation index of the spermatozoa obtained. In this observational study, 98 semen samples from couples undergoing IVF/ICSI cycles were included. Data were collected between April and November 2014 at the ANDROS Day Surgery Clinic, Palermo, Italy. The percentages of DNA fragmentation were 18.30 +/- 10.8 in raw samples, 6.6 +/- 5.7 after DSU, 4.2 +/- 3.8 after PSU, 12.9 +/- 9.9 after DG, and 3.7 +/- 4.0 after DG-SU respectively. Compared to the raw evaluation, all the preparation techniques significantly decreased the total rate of the DNA fragmentation (DSU Z = -8.60, P < 0.008; PSU Z = -8.54, P < 0.008; DG Z = -6.42, P < 0.008, and DG-SU Z = -8.60, P < 0.008, respectively). Comparing them, spermatozoa with intact DNA after PSU and DG-SU were significantly higher than after DSU (Z = -7.12, P < 0.008; Z = -6.59, P < 0.008, respectively) and after DG (Z = -8.41, P < 0.008; Z = -8.60, P < 0.008, respectively). The difference between PSU and DG-SU was not significant (Z = -2.21, P = 0.03). There are, above all, two techniques of sperm preparation which allow for the recovery of spermatozoa with the lowest DNA fragmentation rate. Furthermore, given low costs and reduced time, we believe that PSU is the best option in the treatment of semen samples during IVF/ICSI.