Measurement of sperm DNA fragmentation using bright-field microscopy: comparison between sperm chromatin dispersion test and terminal uridine nick-end labeling assay

ObjectiveTo compare sperm chromatin dispersion (SCD) test with terminal deoxynucleotidyle transferase-mediated terminal uridine nick-end labeling (TUNEL) assay in assessing DNA fragmentation in human sperm through bright-field microscopy.DesignProspectively designed, side-by-side comparative study.SettingMedical genetics laboratory in a provincial research institution.Patient(s)Sixty male patients presented for infertility evaluation and 30 fertile, volunteer sperm donors.Intervention(s)Semen analysis, SCD test, and TUNEL assay on the same semen sample and on the same spermatozoa.Main Outcome Measure(s)Sperm DNA fragmentation, determined by SCD test score or TUNEL assay score.Result(s)Sperm chromatin dispersion test and TUNEL assay identified similar proportions of sperm cells with DNA fragmentation in the same semen samples. When the SCD test and TUNEL assay were performed simultaneously on the same spermatozoa, TUNEL-negative sperm showed a large halo, whereas TUNEL-positive sperm showed no halo after Diff-Quik staining. However, in some sperm cells, DNA damage was detected by the SCD test but not by the TUNEL assay.Conclusion(s)Sperm chromatin dispersion test and TUNEL assay are both effective in detecting sperm DNA damage. Using bright-field microscopy, the SCD test appears to be more sensitive than the TUNEL assay.