Flow cytometric measurement of sperm nuclear DNA fragmentation in infertile men with normal standard sperm parameters

Abstract

Background Male-factor infertility plays a role in approximately 50% of infertile couples. In at least 30% of cases, repeated standard semen analyses of the male partner of an infertile couple reveal normal results. When diagnostic work-up of the female partner is also normal, they are classified as idiopathic. The objective of this study was to evaluate the levels of sperm nuclear DNA fragmentation in a population of infertile men with normal standard semen parameters and to compare their results with those from men who had abnormal semen parameters, as well as with a control group of fertile men. Methods Semen samples were obtained from 202 infertile men and 30 fertile donors. Standard semen analysis was performed according to the World Health Organization guidelines. Flow cytometry has been extensively used to study sperm DNA fragmentation and the results are expressed as the percentage of sperm DNA fragmentation index (DFI). Results Of the 202 patients, 48 (23.8%) had normal standard sperm parameters, while 154 (76.2%) had an abnormality in one or more of these parameters. DFI in infertile men with normal sperm parameters was significantly higher than in fertile donors ( p = 0.03), but not significantly different from infertile men with abnormal sperm parameters ( p = 0.10). There were statistically significant negative correlations between DFI and the percentage of motile sperm from infertile men with abnormal and normal semen parameters, but not in fertile donors ( r = −0.26, p = 0.001 and r = −0.48, p = 0.0001, respectively). Conclusion Sperm from infertile men with normal standard sperm parameters may have significant levels of DNA fragmentation that are comparable to levels in infertile men with abnormal sperm parameters. Sperm DNA fragmentation analysis is an independent test of sperm quality and has an important diagnostic value in the evaluation of male infertility.