Sperm Chromatin Dispersion Test (SCD Test)
Definition - What does Sperm Chromatin Dispersion Test (SCD Test) mean?
The sperm chromatin dispersion (SCD) test determines the capacity of the sperm chromatin (genetic material) to disperse, which helps in identifying sperm DNA fragmentation (sperm DNA damage). The greater the size of chromatin dispersion, the less the extent of the DNA fragmentation. Sperm DNA is contained in the sperm head. Sperm DNA fragmentation may be the underlying factor for unexplained infertility and may be associated with chromosomal abnormalities (aneuploidy).
FertilitySmarts explains Sperm Chromatin Dispersion Test (SCD Test)
During the SCD test, the sperm is exposed to hydrochloric acid to denature the chromatin, and to convert the double-stranded DNA into a restricted single-stranded DNA. After denaturing, a solution is used to lyse (break) the DNA that yields relaxed DNA loops. These loops prevent dispersion of chromatin into the nearby areas. The level of DNA fragmentation is measured by assessing the size of the chromatin dispersion using fluorescence or optical microscopy. The extent of DNA damage is inversely proportional to the level of dispersion.
The SCD test is a reliable and sensitive method of predicting the IVF outcome and pregnancy rates. However, the excessive ovarian stimulation during IVF and intracytoplasmic sperm injection enhances recruitment of good-quality eggs after they are fertilized by a DNA-defective sperm. This, in turn, may mask the detection of the defective sperm. The SCD test may not be as accurate as other tests employed to assess DNA fragmentation.