The 6th edition of the WHO manual of semen analysis, along with the American Urological Association (AUA) and European Association of Urology (EAU)guidelines, acknowledges sperm DNA fragmentation (SDF) testing as one of the most critical additions to male infertility evaluation. SDF refers to single-stranded or double-stranded breaks in the genome of spermatozoa. Because the mature male gamete lacks the ability to repair DNA damage, these breaks tend to persist and can negatively influence the male reproductive potential and outcomes. Men with high SDF are less likely to conceive naturally, have significantly increased risk of recurrent pregnancy loss (RPL) and have poor outcomes after assisted reproductive technologies (ART), IUI or IVF.
Three primary mechanisms that can lead to SDF are abortive apoptosis, defective chromatin maturation and oxidative stress. Damage to the sperm DNA can occur within the testes, during passage along the reproductive ducts, after ejaculation during sperm processing, or during cryopreservation. SDF is found to be significantly higher among infertile men with varicocele, male genital tract infection, advanced age, smoking, obesity, radiation and environmental toxin exposures.
Assays that can be used to evaluate SDF vary greatly in both the method and the type of damage they are detecting. Terminal deoxynucleotidyl transferase (dUTP) nick end labelling (TUNEL) and single cell gel electrophoresis (Comet) assays directly assess the presence of single and/or double strand breaks in the DNA, whereas acridine orange flow cytometry (AO FCM) and sperm chromatin dispersion test (SCD) assays detect the susceptibility of chromatin to treatment by acid.
Testing for SDF should be done after 2-5 days of ejaculatory abstinence and should be performed within 30-60 minutes after liquefaction or immediately after thawing. Due to the heterogeneity and variability, the WHO manual does not provide the exact cut-off to differentiate the normal and elevated SDF. A cut-off level of 20% can be used to distinguish fertile from infertile men. Since SDF is only partially related to semen quality, it could represent an important addition in the work-up of male infertility.
Indications for SDF testing | Management of high SDF |
Unexplained or idiopathic male infertility Recurrent pregnancy loss Clinical varicocele Lifestyle risk factors Before or after failure of ART- IUI, IVF, ICSI Recurrent pregnancy loss after ICSI Sperm freezing | Lifestyle advice and modification Use of antioxidants Recurrent ejaculation Treatment of underlying conditions- varicocelectomy, antibiotics Use of ICSI if SDF persistently elevated Another method for sperm selection after failed ICSI- Zymot Testicular sperm for failed ICSI |
Figure 1: Sperm Chromatin Dispersion test showing normal & fragmented sperms
Authored by Dr Sonia Malik, Vandana Mohan, Nova IVF Fertility Center, Delhi