Several different tests use different technologies to identify and quantify sperm DNA damage:
Sperm chromatin dispersion (SCD) testing. In this process, sperm are carefully denatured — or chemically degraded — and examined under a high-powered microscope to identify the “halos” formed by loops of intact DNA. (Sperm with damage will not produce a halo.) This is the type of testing used in Legacy’s Advanced Semen Analysis.
Single cell gel electrophoresis assay (SCGE), also known as the comet assay. In this process, the cell membrane around sperm is broken down. Fragmented strands of DNA form a “tail,” like that on a comet, the presence and size of which indicates DNA damage.
Sperm chromatin structure assay (SCSA). A sperm chromatin structure analysis is a process in which sperm cells are stained and placed in the path of a laser beam. The laser will cause the dye to emit fluorescent light of a certain color: green indicates sperm with non-detectable levels of fragmented DNA, while yellow and red indicate moderate to high levels of sperm DNA fragmentation.
Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. In this test, an enzyme that attaches to broken DNA strands is “tagged” with fluorescent dye and added to sperm cells. Under a laser light, the cells with DNA damage will emit a different color than those with intact DNA.
These tests are typically performed in a speciality lab. Even if you collect a semen sample at your fertility clinic, it will be shipped to the lab for sperm DNA fragmentation testing.