Sperm DNA fragmentation (SDF) tests measure the amount of DNA damage in sperm, providing insight into sperm quality beyond what standard semen analysis can show. There is currently no single “gold-standard” test, and each method detects different types of DNA breaks and varies in complexity and accuracy (Llácer et al. 2025).
- TUNEL (Terminal deoxynucleotidyl transferase dUTP Nick End Labeling) directly labels broken DNA strands, making it highly sensitive for detecting a wide range of damage, though results can vary depending on how samples are handled.
- SCSA (Sperm Chromatin Structure Assay) uses fluorescent staining to measure how easily sperm DNA unwinds under stress, producing a DNA fragmentation index (DFI) that is reproducible and often used in clinical research.
- SCD (Sperm Chromatin Dispersion) is a simple, lower-cost test where sperm with intact DNA form visible halos under a microscope, while damaged sperm do not. It’s widely used in clinics but less sensitive than other methods.
- Comet Assay (Single-Cell Gel Electrophoresis) provides detailed detection of both single- and double-strand breaks by observing DNA migration patterns under an electric field. It is very sensitive but technically demanding and mainly used in research.
Each test has its strengths and limitations, and the choice depends on the clinical setting, resources available, and specific questions being asked about sperm quality.