Beyond normal sperm testing: What other tests can be done on sperm and are they helpful?

A basic semen analysis – compromising sperm count, sperm motility and morphology (the shape and size of sperm) is the strongest predictor of likelihood of pregnancy when considering male factor fertility. However, you may have seen or heard about extra tests of sperm function and be wondering what they are, or if they are useful – particularly if you are being asked to pay for these extra tests.

Tests for Antisperm Antibodies (ASAB)

Antisperm antibodies (ASAB) are formed when your body sees your own sperm as “foreign”, and mounts an immune response against them (attacks them). They are commonly seen in men who have suffered testicular trauma, had genital infections, or have undergone surgery in that region – such as a vasectomy. However they can also occur without any of these known factors.

• Severe/high levels of ASAB: Typically when viewed under a microscope, semen samples from men who have severe ASAB demonstrate a classic “held and shaking” motion – the sperm look as if something is holding onto their tails as they try to swim away. You also commonly see the sperm agglutinating – or sticking together in large clumps. This gives rise to poor sperm motility (movement) which could prevent the sperm reaching the egg. ASABs may even prevent fertilisation if the sperm does actually reach the egg.
• Low levels of ASAB: Samples from men with low levels of ASAB may not show any visible sign of it when viewed under a microscope, so some laboratories recommend routine testing of all samples for ASAB, or you may be offered the test at additional cost to yourself.

How does the ASAB test work?

Other than directly observing evidence of ASAB as detailed above, there are several ways of measuring the actual levels of ASAB in either semen, or a blood sample. The most commonly used direct test used in semen samples is called a Mixed Antiglobulin Reaction (MAR) test.

Whichever type of test is utilised, the one thing all the tests have in common is that they are not terribly reliable (often giving false positives-show a problem when there isn’t one, or false negatives-miss a problem when there’s one there) and can be highly subjective – i.e. two different people could interpret the same result in different ways. Because of a lack of good clinical evidence, there are currently no agreeable reference values for the number of sperm that need to be deemed antibody positive before a diagnosis of ASAB can be made. The World Health Organisation (WHO) suggests that with the MAR test, more than 50% of the sperm tested must show a reaction to the antibody test for it to be considered clinically significant – i.e. likely to hinder your ability to conceive.

Is the ASAB test helpful?

There is much discussion over what a positive ASAB test actually means and how you could treat it if diagnosed. There is some evidence that an ASAB test can be an issue for some people in extreme cases, but low levels of ASAB are not uncommon and their role in infertility is still uncertain. The presence of ASAB, if diagnosed, rarely leads to a change in the way we would treat a couple trying to conceive.

For this reason, in the UK (for example), NICE guidelines state that men should NOT be offered an ASAB test, nor should they be prescribed high dose steroids as treatment. Other regions of the world may make similar or different recommendations.

Given how unreliable these tests are, and the fact that you may have to pay for this type of testing yourself – some men would like to have the test done as they feel that knowing a potential reason for their infertility is psychologically beneficial. However you should be aware of the test limitations and understand that it is prone to giving inaccurate results, and so will not normally alter your fertility treatment pathway.

Tests of Sperm Viability (or vitality)

Some men produce lots of sperm, but they show poor motility (movement) – or in some cases no motility at all. But you cannot assume that just because a sperm isn’t moving (immotile), it isn’t alive. We expect to find that about 60% of sperm in a sample are viable (alive), regardless of if they are moving or not.

It is important to note that determining accurate viability requires that testing be performed following only 2-3 days sexual abstinence. Not ejaculating for long periods of time and then providing a sample for testing will inevitably lead to an increased proportion of dead/immotile sperm in the sample and give you an unreliable viability result. This is why it is so important to follow instructions about preparing for you test, and being accurate about telling the clinic when your previous ejaculation as at the time of the sperm test.

Laboratories undertake a viability test if sperm motility is lower than expected – the WHO recommends viability testing when fewer than 40% of sperm in a sample are moving. In practise this is a very high threshold, many laboratories set their own thresholds and wouldn’t routinely test for viability unless it was far lower (less than 15-20% of sperms are motile).

How does the test of sperm viability work?

A dye test is most commonly used in a diagnostic laboratory as it is reliable and easy to use. When a sperm cell is alive, its surrounding cell membrane actively prevents the bright pink dye from entering the cell – these sperm remain white when viewed down a high power microscope. However if the sperm cell is dead, the dye will be able to enter the cell, and will appear pink when viewed under the microscope. In this way we can assess the proportion of live (white) vs dead (pink) sperm.

Is this test helpful?

The test result may help to diagnose specific problems or determine if further more complex testing is required.

If the test shows that lots of sperm are alive, but not moving, it could indicate that there is a problem with the structure of the sperm tail. This could be due to a genetic condition and would require further testing.

If the test shows a high percentage of the sperm are dead, it may indicate an issue with the environment in which the sperm are stored in the epididymis (part of the testis), and in some cases changes in lifestyle could improve this. Alternatively it could simply be that you have not provided a sample that meets the acceptance criteria of only 2-3 days sexual abstinence. If this is the case, repeat testing is advisable.

Tests for Sperm DNA fragmentation

A normal sperm head contains tightly packaged DNA – the genetic material that will ultimately combine with the egg DNA to create an embryo. It is normal for some DNA damage to occur as the sperm is transported through the male reproductive system, and this is known as DNA fragmentation. Small amounts of damage can be repaired once the sperm DNA enters the cytoplasm of the egg.

So what causes DNA fragmentation? Many causes have been proposed – many are complex and at a cellular level and involve increased levels of Reactive Oxygen Species (ROS). These are a type of unstable molecule that at high levels may cause damage to DNA. It has also been suggested that exposure to environmental toxins and pollutants, cigarette smoke, increased scrotal temperature, chemo-radiation, certain drugs, varicocele and advanced male age may all contribute to increased ROS levels.

This is a relatively new area of interest and in recent years there has been much research looking at the clinical importance of DNA fragmentation levels in sperm, and how this could impact on male fertility. There is certainly growing evidence that higher levels of DNA fragmentation can be associated with male factor infertility, but the exact causes and clinical significance are still unclear.

How does the test for sperm DNA fragmentation work?

There are many ways of testing for sperm DNA fragmentation, some more reliable than others. They generally work in two different ways. Some measure DNA fragmentation levels directly through the use of probes and fluorescent dyes that attach to the fragmented sperm DNA which can then be looked at under a microscope. Other tests measure how susceptible the sperm DNA is to being fragmented by exposing them to acids to denature the proteins.

Is this test useful?

Whilst there is acknowledgement across the profession that DNA fragmentation is an area of interest when investigating male infertility and could indeed be a contributing factor, at present there is not enough robust clinical evidence to back this up.

There are no validated reference values for any of the tests available – i.e. we do not know for sure at what level the DNA fragmentation has to be before we can say it definitely causes a problem in male fertility. There is also currently no proven treatment or solution to high levels of sperm DNA fragmentation, so in practise – what do you do with a test result that indicates high fragmentation levels? For this reason, none of the worldwide professional bodies currently recommend the routine use of DNA fragmentation tests in the evaluation and treatment of infertile couples.

The above should be borne in mind if you are considering paying for this type of testing – some men would like to have the test done as they feel that knowing a potential reason for their infertility is psychologically beneficial. However you should be aware of the test limitations and understand that a high DNA fragmentation result will not normally alter your fertility treatment pathway.