Insights on the predictive accuracy of the sperm DNA fragmentation tests on male infertility

Dr. El-Sakka in his commentary on the “Clinical utility of sperm DNA fragmentation testing: practice recommendations based on clinical scenarios” by Agarwal et al. (1), has generally acknowledged the importance of clinical scenarios in remedying the current sperm DNA fragmentation (SDF) debate and identifying the proper indications for performing the SDF testing method. He also addressed the current drawbacks of SDF that still impede its routine use in clinical practice. SDF test sensitivity and specificity in predicting male infertility as well as the burden of its cost were among the drawbacks discussed by Dr. Elsakka in his commentary.

Conventional semen analysis remains the cornerstone of male fertility evaluation. However, despite its ability to provide an overall assessment of male fertility potential, it fails as an accurate predictor of fecundity. Notwithstanding the periodic refinements in semen analysis techniques and cutoff values in the form of WHO guidelines for semen assessment, up to 30% of men with normal semen parameters remain infertile (2). These findings have triggered the search for additional diagnostic tools that could improve our ability to predict pregnancy. Of all the sperm function tests, SDF is perhaps the only test that has withstood the test of time in terms of its applicability in male fertility evaluation. Since the first pioneering publication in Science with its cover photomicrograph showing florescent flow-cytometric red and green stained sperm and reporting a significant difference in sperm DNA integrity between fertile and subfertile bulls and men (3), the study of sperm DNA integrity has been constantly evolving. In the years since this first report, several other testing modalities were developed examining different aspects of sperm DNA damage that enhanced our understanding of the paternal genomic contribution to the fetus (1). At the same time, the preponderance of testing modalities having multiple cutoff values have been considered as a disadvantage to the applicability of SDF in clinical practice and was perhaps the principal factor behind failure of reproductive societies to advocate its routine use in the evaluation of male infertility (4). Recently, with the refinements in the testing methodologies and their performance in appropriate clinical scenarios, we are witnessing an improvement in SDF test validity and predictive accuracy (5-7) and are therefore expecting an update to the best practice recommendations.

For example, TUNEL has been found to be a valid independent test of fertility capable of predicting pregnancy both naturally and after ART with a sensitivity of 85% and a specificity of 89% (8). A sperm chromatin dispersion (SCD) test cutoff value of 25.5% was found to have a sensitivity of 86.2% and a negative predictive value of 72.7% (P=0.02) in predicting successful ART treatment (9). Likewise, a sperm chromatin structure assay cutoff value of 30% was found to carry a significant predictive power to the likelihood of pregnancy both in vivo and after ART, where patients with a SDF <30% were 7.1 times [95% confidence interval (CI), 3.37–14.91] more likely to achieve a pregnancy in vivo and ~2.0 times (95% CI, 1.10–2.96) more likely to achieve pregnancy after ART (10). A recent meta-analysis examining the diagnostic accuracies of different SDF methods for male infertility reported a TUNEL sensitivity and specificity of 77% and 91%, respectively [area under curve (AUC) =0.95] and a combined sensitivity and specificity for SCD and Comet of 77% and 84%, respectively (AUC =0.85) (7).

Dr. El-Sakka had commented about the controversy that still exists regarding the correlation between SDF measures and semen parameter results. On the contrary, compelling evidence from systemic reviews and meta-analyses has consistently demonstrated a significant negative correlation between these two variables (11-13). Instead, the real question here is not whether SDF correlates well with semen parameters. Rather, if SDF can be utilized as a fertility predictor in different clinical scenarios. Such an influence has been most thoroughly investigated in the setting of ARTs. While Dr. El-Sakka has cited Lin et al. (14) who failed to find a significant correlation between SDF (measured with SCSA), high DNA stainability (HDS), and outcomes of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), the systemic reviews and meta-analyses [reviewed by Agarwal et al. (1,12,15-18)] have consistently demonstrated a significant negative association between SDF levels and pregnancy rates with IUI [odds ratio (OR) =9.9; 95% CI, 2.37–41.51; P<0.001]) and IVF (OR =1.57; 95% CI, 1.18–2.07; P<0.05) (17), and a significant positive association between SDF levels and miscarriage rate after IVF and ICSI (combined OR =2.48, 95% CI, 1.52–4.04; P<0.0001) (17). These controversies are anticipated in medical literature and can be explained by variations in research methodologies or specifically in this case, the method of SDF testing being utilized.

Cost of a procedure is an important aspect that has to be considered in any treatment decision making. Unfortunately, like most fertility treatments which are not covered by medical insurance, the added cost of SDF testing may impose additional burden on the couple’s financial demands. Nevertheless, the expenses for SDF testing are perhaps a fraction of the cost of other fertility treatments such as ART procedures or surgical varicocele ligation. The principle aim of the clinical guideline article by Agarwal et al. (1) is to elucidate the circumstances were SDF testing result is most influential on treatment decisions, therefore, consequently on the overall treatment cost. For example, SDF results may aid in a recommendation for ART procedure and/or treatment associated with the highest likelihood of pregnancy thereby eliminating any unnecessary cost from less successful ART modalities. Furthermore, the SDF result would also help in selecting patients who are most likely to benefit from varicocele ligation eliminating unnecessary surgery.

Acknowledgements

None.

Footnote

Conflicts of Interest: The authors have no conflicts of interest to declare.

References

1. Agarwal A, Majzoub A, Esteves SC, et al. Clinical utility of sperm DNA fragmentation testing: practice recommendations based on clinical scenarios. Transl Androl Urol 2016;5:935-50. [Crossref] [PubMed]
2. Gelbaya TA, Potdar N, Jeve YB, et al. Definition and epidemiology of unexplained infertility. Obstet Gynecol Surv 2014;69:109-15. [Crossref] [PubMed]
3. Evenson DP, Darzynkiewicz Z, Melamed MR. Relation of mammalian sperm chromatin heterogeneity to fertility. Science 1980;210:1131-3. [Crossref] [PubMed]
4. Practice Committee of the American Society for Reproductive M. The clinical utility of sperm DNA integrity testing: a guideline. Fertil Steril 2013;99:673-7. [Crossref] [PubMed]
5. Sharma R, Ahmad G, Esteves SC, et al. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay using bench top flow cytometer for evaluation of sperm DNA fragmentation in fertility laboratories: protocol, reference values, and quality control. J Assist Reprod Genet 2016;33:291-300. [Crossref] [PubMed]
6. Ribas-Maynou J, Garcia-Peiro A, Fernandez-Encinas A, et al. Comprehensive analysis of sperm DNA fragmentation by five different assays: TUNEL assay, SCSA, SCD test and alkaline and neutral Comet assay. Andrology 2013;1:715-22. [Crossref] [PubMed]
7. Cui ZL, Zheng DZ, Liu YH, et al. Diagnostic Accuracies of the TUNEL, SCD, and Comet Based Sperm DNA Fragmentation Assays for Male Infertility: a Meta-analysis Study. Clin Lab 2015;61:525-35. [Crossref] [PubMed]
8. Chenlo PH, Curi SM, Pugliese MN, et al. Fragmentation of sperm DNA using the TUNEL method. Actas Urol Esp 2014;38:608-12. [Crossref] [PubMed]
9. Lopez G, Lafuente R, Checa MA, et al. Diagnostic value of sperm DNA fragmentation and sperm high-magnification for predicting outcome of assisted reproduction treatment. Asian J Androl 2013;15:790-4. [Crossref] [PubMed]
10. Bungum M, Humaidan P, Spano M, et al. The predictive value of sperm chromatin structure assay (SCSA) parameters for the outcome of intrauterine insemination, IVF and ICSI. Hum Reprod 2004;19:1401-8. [Crossref] [PubMed]
11. Evenson D, Wixon R. Meta-analysis of sperm DNA fragmentation using the sperm chromatin structure assay. Reprod Biomed Online 2006;12:466-72. [Crossref] [PubMed]
12. Zini A, Sigman M. Are tests of sperm DNA damage clinically useful? Pros and cons. J Androl 2009;30:219-29. [Crossref] [PubMed]
13. Evgeni E, Charalabopoulos K, Asimakopoulos B. Human sperm DNA fragmentation and its correlation with conventional semen parameters. J Reprod Infertil 2014;15:2-14. [PubMed]
14. Lin MH, Kuo-Kuang Lee R, Li SH, et al. Sperm chromatin structure assay parameters are not related to fertilization rates, embryo quality, and pregnancy rates in in vitro fertilization and intracytoplasmic sperm injection, but might be related to spontaneous abortion rates. Fertil Steril 2008;90:352-9. [Crossref] [PubMed]
15. Agarwal A, Cho CL, Esteves SC. Should we evaluate and treat sperm DNA fragmentation? Curr Opin Obstet Gynecol 2016;28:164-71. [Crossref] [PubMed]
16. Osman A, Alsomait H, Seshadri S, et al. The effect of sperm DNA fragmentation on live birth rate after IVF or ICSI: a systematic review and meta-analysis. Reprod Biomed Online 2015;30:120-7. [Crossref] [PubMed]
17. Zini A. Are sperm chromatin and DNA defects relevant in the clinic? Syst Biol Reprod Med 2011;57:78-85. [Crossref] [PubMed]
18. Robinson L, Gallos ID, Conner SJ, et al. The effect of sperm DNA fragmentation on miscarriage rates: a systematic review and meta-analysis. Hum Reprod 2012;27:2908-17. [Crossref] [PubMed]