There are many sperm tests available; some results will be more relevant to you than others.
Which results should matter to you? Well, it all depends on context of course, and to help you understand sperm tests better, I thought I would post about it below, by highlighting the 4 things we really want to know about sperm.
1. Can the sperm reach the egg?
First things first: the sperm have to reach the egg.
When a couple is having intercourse (or when donor sperm is placed on the cervix), sperm will exposed to the somewhat acidic vaginal milieu. It isn’t a particularly hospitable place for sperm, and many won’t get past this stage. In fact, 99% of sperm will die within 20 minutes.
We want some sperm to be well protected for there to be a chance of pregnancy. Fortunately, they are safer when surrounded by cervical mucous, and by the seminal fluid itself. Therefore we like to see a good volume of seminal fluid, usually between 1.5 and 5.0cc, to be confident that the sperm will be safe enough to have that chance to swim up into the uterus and beyond.
Still, many sperm won’t make it. Probably about 90,000 sperm will get up into the uterus, from an average 90 million or so in the ejaculate. This is why the number of sperm is so helpful, measured as the concentration, usually 20 million/ml or more. When you start with more sperm, it becomes more likely that enough will arrive at the final destination.
Of course, they won’t be able to swim anywhere if they don’t have good motility (usually >40% have normal motility) and they won’t be able to swim quickly and in a straight line if they have an abnormal shape, measured as morphology (usually >30% have normal morphology).
If all four parametes above are normal, it becomes highly likely that the sperm have the ability to reach eggs. Lower-than-average numbers leads us to wonder if the sperm are even being given the chance fertilize eggs at all.
2. Can the sperm penetrate the egg?
Once they get arrive at the end of the fallopian tube, sperm have to stick on, and burrow their way into, the egg. This ability stick-on-and-burrow is not measured by the usual sperm tests (though motility and morphology correlate somewhat with this ability). To find this out with greater accuracy, you will need to do sperm penetration and binding assays. Not every clinic is able to offer this extra level of testing. And to be fair, the most precise way of all to measure this ability is to do IVF, where the lab can watch your sperm try to enter your partner’s eggs.
3. Is the sperm carrying good DNA?
At the end of the day, sperm is just a vector for DNA. When a sperm swims well and penetrates an egg, it will all be for naught if the DNA it carries isn’t able to do the job and help to create a healthy embryo.
The most common way to approximate the quality of the DNA carried by sperm is to do a karyotype, in which we test the man’s DNA in his blood cells or cheek cells. No, a karyotype isn’t the same thing as the DNA in the sperm -errors can be introduced during sperm development that are not found in any other cell in the body- but it is a reasonable place to start. We will also test the man for specific genetic errors (such as cystic fibrosis or Y microdeletions) when clinically indicated.
Yes we would rather test the DNA in individual sperm, but current technology limits our ability to do so. “Five probe FISH analysis”, for example, looks at individual sperm, but it is a highly specialized investigation that only a few centres in North America offer. Though I offer it to some patients, its value seems to be limited and in most situations, the karyotype will be sufficient.
4. Are the epigenetics of the sperm’s DNA intact?
Until recently, we though that our genetic health was determined solely by DNA, but now we realize that how the DNA is held together (imprinting) is critically important too. If the DNA is not “packed together” properly, it may be not interpreted properly….and a variety of different problems (including lack of pregnancy) may result.
We test the epigenetics of sperm through DNA integrity assays, also known as a DNA fragmentation index (DFI) or sperm chromosome structure assay (SCSA). These have proven to be very useful tests in a modern clinical practice when male factor subfertility is suspected.
Here is a summary of the most common tests that we will order for men when confirming their fertility potential. Not all tests are appropriate for all men; ask your doctor which might be right for you.
Standard semen analysis:
Newer sperm tests currently available:
Sperm penetration/binding assays
Direct DNA (FISH) analysis
Autoantibodies to sperm
Frequently ordered mens’ tests:
Karyotype and Y microdeletion
Physical exam/scrotal and transrectal ultrasound to look for varicocele and other testicular anomalies