|Sperm DNA fragmentation testing - Not good enough...yet|
Sperm DNA fragmentation
Fertilization, whether occurring naturally as a result of intercourse or in the laboratory by IVF needs a healthy egg and a healthy sperm. The sperm has received much attention recently. The sperm is necessary to carry DNA from the male to the female egg, allow fusion of the sperm with the egg and even provide the raw materials needed for the egg to start (the centrosome)
Sperm DNA contributes half of the offspring’s genetic material. If the DNA is abnormal in some way such as fragmented DNA, it may cause a breakdown in the reproductive process and therefore lower the chance of a healthy baby.
The DNA in sperm is protected from damage by wrapping itself tightly around proteins inside the sperm head. However, during the maturation of sperm in the male reproductive tract, sperm gradually loses its ability to fix damaged DNA. There is some suggestion that when the DNA is “packaged” correctly, the sperm may be more susceptible to the effect of harmful molecules called “free radicals”.
In addition, there are other factors that may result in an increase in the percentage of spermatozoa with DNA damage. Among them, the most important are cigarette smoking, genital tract infection, testicular cancer, especially Hodgkin’s disease, heat, exposure to pesticides, and air pollution.
Sperm DNA fragmentation Tests
The tests used for the assessment of sperm DNA fragmentation can be divided into direct and indirect tests. The direct tests try to detect the actual DNA breaks, while the indirect tests try to determine the susceptibility of sperm DNA to break after an external insult, such as acid treatment.
Commonly used direct tests:
Commonly used indirect test:
There are very important limitations of all these tests
Sperm DNA fragmentation in IVF
Over the last several years, sperm DNA fragmentation has been promoted as a promising method to predict the outcome of IVF cycles. Numerous studies (some good and some bad) have examined the relationship between sperm DNA fragmentation and pregnancy rates with IVF. Unfortunately, the results have been conflicting In a recent study, doctors combined the results of thirteen studies looking at the impact of sperm DNA fragmentation on IVF pregnancy rates . Although a link was found, it was so weak that it can not be considered clinically important. In other words, there is not enough adequate evidence to discriminate between couples who will or will not conceive in IVF cycles.
Time tells the tale
Looking at the published medical data over time, one can see how the purported impact of sperm DNA fragmentation has changed. Initially, it was reported that there would simply be no pregnancies in med who had high levels of fragmentation. Later, however, the same centers that published data stating there would be no pregnancies, changed their minds and then started to say that pregnancies would occur but that fertilization or embryo development would be lower. The most recent assertion is that it doesn’t affect these other things but that couples will miscarry more often.
It is also important to note that much of the data supporting the use of DNA fragmentation tests have been published by the same centers that are promoting their labs to do these tests. There is an obvious bias here that is rarely mentioned in the medical literature.
Since this type of testing is still considered experimental, most insurance companies will not cover the cost. Sperm DNA fragmentation testing is very expensive, often running 5-10 times more than a semen analysis .
|Last Updated ( Sunday, 13 December 2009 )|