Sperm Testing – including DNA Fragmentation Index (SCSA)
For couples experiencing fertility problems, sperm testing is equally as important for the male, as hormone testing and other investigations are essential for the female, in helping to determine the underlying causes of a couple’s sub-optimal fertility.
Semen analysis
A semen analysis will examine three main factors:
- Sperm count – the number of sperm per ml of ejaculate
- Sperm motility – the sperm’s ability to swim and live forms
- Sperm morphology – the shape of the sperm, to assess for abnormalities
DNA fragmentation index
Sperm DNA fragmentation testing can be performed at the same time as a semen analysis, but it is a separate and essential test that assesses the DNA quality of sperm.
It has little or nothing to do with the parameters that are measured on a routine semen analysis, such as the shape of the sperm or whether the sperm are moving – it is a completely independent variable. Men with otherwise normal semen analyses can have a high degree of DNA damage and men with what was called very poor sperm quality can have very little DNA damage. More importantly, the degree of DNA fragmentation correlates very highly with the inability of the sperm to initiate fertilisation and even if fertilisation occurs, high DNA fragmentation will often results in ceasing embryo development before implantation. Research also shows that even if a pregnancy is acheived, there is a significantly higher likelihood that it will result in miscarriage.
A normal sample has less then 15% of the sperm with DNA damage, ideal is less than 10%. A DFI Between 16% and 29% is considered a fair fertility potential but becomes poorer as it approaches 27%. Men with extremely poor fertility potential have greater then 30% of their sperm damaged – which means that the likelihood of couples achieving a successful birth is around 1% if more than 30% of a male’s sperm are damaged.
The causes of high DNA fragmentation that cause male infertility include:
- chemical/toxin exposure
- heat exposure
- varicocele (varicose veins of the testes)
- infection
- age
- smoking
- testicular cancer
- radiation
- anything that increases the free radical levels in the semen, such as low antioxidant levels and poor lifestyle
It is very important to understand that sperm DNA fragmentation can be improved if the underlying factors are addressed. The goal of complete sperm testing is to seek out the causes of poor sperm quality and try to correct them so conception can occur naturally or to improve the sperm quality for IVF and maximise the chances of success.
By testing for sperm DNA fragmentation, many cases of so-called “unexplained” infertility can now be explained. We find that many couples who have been previously unable to conceive with invasive and costly artificial reproductive technologies such as IVF, GIFT and ICSI achieve success once improvement in the male’s DNA fragmentation is improved.
How is a semen analysis and DNA fragmentation test done
The patient is referred to a specialised fertility facility that does fresh semen semen analysis. It is preferable that the patient does the sample collection at the facility, but if preferred, it can be collected at home as long as it is delivered to the lab within one hour.
The semen analysis is performed immediately by a specialist technician at the lab and the test results are usually available within 1-2 weeks.
The most common way to test for sperm DNA fragmentation is by using Sperm Chromatin Structure Assay or SCSA. If a SCSA is requested at the same time as the semen analysis, the lab will use the same sample to perform the SCSA.
The SCSA is done by applying a stress (low pH) and then the sperm are labeled with a special dye that only attaches to the ends of broken DNA within the sperm cell. If the DNA is intact, then no dye will attach to the sperm. A machine called a ‘flow cytometer’ is used to test ten thousand sperm from the sample and the percentage of damaged sperm is tested, giving an index known as the DNA fragmentation Index (DFI).