Abstract
Infertility affects 15% of all couples. Although male infertility factors with reduced semen quality are contributing to about half of all involuntary childlessness, the value of standard semen parameters in prediction of fertility in vivo and choice of proper method for assisted reproduction is limited. In the search for better markers of male fertility, during the last 10 years, assessment of sperm DNA integrity has emerged as a strong new biomarker of semen quality that may have the potential to discriminate between infertile and fertile men. Sperm DNA Fragmentation Index (DFI) as assessed by the flow cytometric Sperm Chromatin Structure Assay (SCSA) can be used for evaluation of sperm chromatin integrity. The biological background for abnormal DFI is not completely known, but clinical data show that DFI above 30% is associated with very low chance for achieving pregnancy in natural way or by insemination, but not in vitro. Already when the DFI is above 20%, the chance of natural pregnancy may be reduced, despite other sperm parameters being normal. Thus this method may explain a significant proportion of cases of unexplained infertility and can be beneficial in counselling involuntary childless couples need of in vitro fertilisation.
Highlights
In western countries up to one-forth of couples in reproductive age are seeking medical help for involuntary childlessness [1]
Studies have demonstrated that these four sperm DNA integrity tests, the structure assay (SCSA), TUNEL, Comet, and sperm chromatin dispersion (SCD) assays, generally correlate moderately with each other, which indicates that the tests likely are expressing different aspects of sperm DNA damage
Whilst the proportion of children born per cycle was 19.0% when the DNA Fragmentation Index (DFI) value was below 30%, those with a DFI value above 30% only had a takehome-baby rate of 1.5%
Summary
In western countries up to one-forth of couples in reproductive age are seeking medical help for involuntary childlessness [1]. IVF and ICSI are symptomatic treatments where only 25–30% of the treatments result in a delivery [6] One explanation to this limited success can be the lack of markers to find the underlying causes to subfertility and a lack of methods to identify the type of ART treatment providing the most optimal chances of pregnancy in a given couple. During the last decade the search for better predictors of male fertility has resulted in an increased focus on the sperm DNA integrity [7, 8]. The clinical value of these different tests varies; SCSA, first described by Evenson et al [13] is shown to be an independent marker of fertility in vivo and may help in selection of the most effective ART treatment in each individual couple [15]. The crossing-over process during spermatogenesis or deficiencies in the protamination process will likely make sperm more vulnerable to oxidative stress at a later occasion
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