Sperm DNA Fragmentation Testing in the Era of Assisted Reproduction: Clinical Utility, Thresholds, and Management Strategies

Sperm DNA fragmentation (SDF) has emerged as a clinically important biomarker in male infertility evaluation, offering diagnostic information beyond conventional semen analysis. The inclusion of SDF testing into the World Health Organization 6th edition laboratory manual underscores its growing relevance in reproductive medicine. Elevated SDF levels have been associated with reduced fertilization rates, impaired embryo quality, decreased pregnancy rates, and increased miscarriage risk, particularly in couples with otherwise normal semen parameters. This narrative review examines current SDF testing methodologies, focusing on clinical applicability and diagnostic thresholds. We compared four principal testing modalities— erminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL), sperm chromatin structure assay (SCSA), sperm chromatin dispersion (SCD) test, and Comet assay, by evaluating their technical characteristics, reproducibility, and predictive value for assisted reproductive technology (ART) outcomes. The evidence demonstrates that, although universal thresholds remain elusive, methodology-specific cut-off values provide meaningful clinical guidance: TUNEL (>16.8–20%), SCSA DNA fragmentation index (>25%), SCD (15–25%), and alkaline Comet assay (>26%). Clinical indications for SDF testing include recurrent pregnancy loss, unexplained infertility, and recurrent ART failure. Evidence-based management strategies encompass varicocelectomy, short ejaculatory abstinence protocols, antioxidant therapy, and testicular sperm extraction for refractory cases. Interpretation should be contextualised by female partner age, oocyte quality, and planned ART modality, as these factors substantially influence the clinical impact of elevated SDF. By integrating findings of recent literature, this review provides a practical, evidence-based framework for the judicious application of SDF testing, including patient selection criteria, methodological considerations, and stepwise therapeutic interventions.