The role of sperm chromatin structure assay in improving the diagnosis of male factor infertility in Benin city

Background: Male factor infertility accounts for about 30% of infertility cases worldwide. In Nigeria, evaluation relies almost exclusively on seminal fluid analysis (SFA), which does not assess chromatin integrity; up to 15% of men with normal SFA remain sub-fertile from unrecognized chromatin abnormalities. This study aimed to determine the prevalence of abnormal sperm chromatin structure, its relationship with semen parameters, and associated risk factors among male partners of infertile couples in Benin City, using the Sperm Chromatin Structure Assay (SCSA). Methods: In this cross-sectional study, 120 male partners of infertile couples attending the Infertility Clinic, University of Benin Teaching Hospital from April to July 2026, underwent SFA and SCSA (flow cytometry with acridine orange staining) to determine the DNA Fragmentation Index (DFI). Data were analysed using descriptive statistics, correlation, and logistic regression; p<0.05 was significant. Results: Mean age was 45.3±8.0 years and mean DFI was 22.4±7.1%. Abnormal DFI (>25%) occurred in 39.2% (95% CI 30.9-48.1%) of participants. DFI correlated negatively with motility, progressive motility, morphology, and vitality (all p<0.05), but not with volume or sperm count. Notably, 21.3% of men with normal SFA had abnormal DFI. Cigarette smoking was the only independent predictor of abnormal DFI (adjusted OR 3.57, p=0.002); no seminal parameter achieved acceptable diagnostic accuracy (AUC≥0.70) as a DFI proxy. Conclusions: Abnormal sperm chromatin structure is common among Nigerian men with infertility and is incompletely captured by semen analysis alone. SCSA should be incorporated into male infertility evaluation, particularly for semen with low vitality or progressive motility. Also, instructive to prioritize smoking cessation counselling as a modifiable risk factor.