Effect of varicocelectomy on sperm DNA fragmentation rates in infertile men with clinical varicocele: a systematic review and meta-analysis

Abstract

Study question Does varicocelectomy improve sperm DNA quality in men with infertility and clinically detected varicoceles?

Summary answer Varicocelectomy reduces sperm DNA fragmentation (SDF) rates in infertile men with clinical varicocele.

What is known already Varicocele has been linked to male infertility through various non-mutually exclusive mechanisms, including an increase in reactive oxygen species (ROS) production that may lead to sperm DNA damage. Damage to sperm DNA may result in longer time-to-pregnancy, unexplained infertility, recurrent pregnancy loss, and failed intrauterine insemination or in vitro fertilization/intracytoplasmic sperm injection. Therefore, interventions aimed at decreasing SDF rates, including varicocele repair, have been explored to improve fertility and pregnancy outcomes potentially, either by natural conception or using medically assisted reproduction.

Study design, size, duration Systematic review and meta-analysis

Participants/materials, setting, methods We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Our systematic search included PubMed/Medline, EMBASE, Scielo, and Google Scholar to identify all relevant studies written in English and published from inception until October 2020. Inclusion criteria were studies comparing SDF rates before and after varicocelectomy in infertile men with clinical varicocele. Articles were included if the following SDF assays were utilized: SCSA, TUNEL, SCD test, or alkaline Comet.

Main results and the role of chance Thirteen studies fulfilled the inclusion criteria and were selected for the analysis. The estimated weighted mean difference of SDF rates after varicocelectomy was –6.58% (13 studies, 95% CI –8.33%, –4.84%; I2=90% p < 0.0001). Subgroup analysis revealed a significant decrease in SDF rates using SCSA (eight studies, WMD –6.80%, 95% CI –9.31%, –4.28%; I2=89%, p < 0.0001), and TUNEL (three studies, WMD –4.86%, 95% CI –7.38%, –2.34%; I2=89%, p < 0.0001). The test for subgroup difference revealed that pooled results were conservative using the above SDF assays. Comet and SCD tests were used in only one study each; thus, a meta-analysis was not applicable. The studies were further categorized by the surgical technique (microsurgical versus non-microsurgical). This subgroup analysis showed a significant decrease in SDF rates using microsurgical technique (10 studies, WMD –6.70%, 95% CI –9.04%, –4.37%; I2=91%, p < 0.0001). After varicocelectomy, SDF rates were also decreased when non-microsurgical approaches were used, albeit the effect was not statistically significant (2 studies, WMD –6.84%, 95% CI –10.05%, 1.38%; I2=86%) (Figure 3). The heterogeneity was not materially affected by performing analyses by the above subgroups, suggesting that the SDF assay and surgical technique do not explain the inconsistency in the treatment effect across primary studies.

Limitations, reasons for caution There were no randomized controlled trials comparing varicocelectomy to placebo for alleviating SDF levels. Heterogeneity was high, which may be explained by the low number of included studies. Pregnancy data are not available in most studies, thus the impact of reduced SDF after varicocelectomy on pregnancy rates unclear.

Wider implications of the findings: Our study indicates a positive association between varicocelectomy and reduced postoperative SDF rates in men with clinical varicocele and infertility, independentetly of the assays used to measure SDF. These findings may help counsel and manage infertile men with varicocele and high SDF levels.