Sperm Chromatin Structure Assay – SCSA

Around 10% of all couples are affected by infertility. Approximately 30% of infertility cases are caused by a female factor, another 30% are caused by a male factor, and 30% of cases are related to both female and male factors. The remaining 10% of infertility is categorized as “unexplained infertility” where the cause is not known. The Sperm Chromatin Structure Assay (SCSA) test is used to measure the level of DNA fragmentation in sperm, which can be useful for treating male factor infertility.

In previous years, the methods used to evaluate male infertility were limited to a semen analysis, which measured sperm count, shape, and movement. Researchers now know that sperm with certain levels of DNA fragmentation indicated reduced male fertility. The SCSA test measures the level of this fragmentation in the sperm, which will improve the diagnosis and treatment for male infertility.


SCSA Results

Research proves that sperm with high levels of DNA fragmentation do not tend to produce a successful pregnancy. A review of data on several hundred semen samples found that clients with a DNA fragmentation level of more than 30% were likely to have seriously reduced fertility potential. In addition, these clients had a significant reduction in term pregnancies and more miscarriages. Sperm can have abnormal DNA even when it appears normal according to traditional semen analysis parameters.

To achieve the best measurement of male fertility potential, the SCSA reports the percentage of the four major populations of sperm in a semen sample. These are:

  • Sperm with a low level of DNA fragmentation.
  • Sperm with immature chromatin related to less condensation, which allows for a higher degree of DNA stainability.
  • Sperm with increased susceptibility to DNA denaturation, which is classified based on defragmentation.

The SCSA is performed using the flow cytometer instrument. This device stains cells with fluorescent dye and sends them through a glass channel in liquid form. The cells will pass through a laser beam, which causes the dye to emit a fluorescent light of a particular color. The colors measured are green and red. Green sperm indicates a low level of fragmented DNA, and red sperm indicate high levels of fragmented DNA.


Advantages of the SCSA

The SCSA offers many advantages over other clinical assays for many reasons. These include:

  • The SCSA can measure around 5,000 individual sperm in just a few seconds.
  • The data provided can be used for diagnostic and prognostic evaluation of the man’s potential for fertility.
  • The data are from machine-defined, objective criteria and not biased by human eye measurements.
  • The data have a higher level of repeatability than that of other semen parameter.
  • Test randomly measures all cell types in the semen sample as opposed to only washed specimens.


Causes of DNA Fragmentation

In a recent study involving more than 700 in vitro fertilization cases where intracytoplasmic sperm injection (ICSI) was used, pregnancy occurred in less than 1% of cases with damaged DNA. Another study found that more than 30% of sperm with damaged DNA lacked fertility potential. Many factors explain why a certain person has high DNA fragmentation in the sperm that results in infertility. When looking at various SCSA studies, factors identified were:

  • Age of the man
  • Length of sexual abstinence
  • Smoking history
  • Exposure to environmental pollutants
  • Leukocytospermia
  • Febrile illness
  • Testicular cancer
  • Testicular exposure to prolonged heat
  • Drug use
  • Exposure to radiation or chemicals