Male Fertility Tests
Male fertility tests are also known as sperm tests or semen tests. Male fertility tests have come along way in recent years. The earliest male fertility test, the semen analysis, did not change much over the course of many decades.
The American Society for Reproductive Medicine recommends that at least two sperm tests be performed in the evaluation of an infertile male. The semen is collected by masturbation on separate days are recommended. The ejaculate is collected in a sterile container provided by the clinic or laboratory and should be examined within 30 minutes of collection.
Components of the semen test
- Liquefaction (conversion into a liquid): complete within 60 minutes
- Appearance: homogeneous, gray-opalescent ejaculate
- Volume (amount): 2 milliliter or more
- Concentration: 20 million per milliliter
- Total count: 40 million sperm per ejaculate
- Motility (movement): 50% of the total number of sperm
- Progressive motility: 25% of the total number of sperm
- Consistency: Not viscous (not thick)
- Morphology (structure): More than 14% have a normal appearance
Semen tests became much more sophisticated with the advent of the computerized sperm tests.
Computerized Semen Test
For many years, evaluation of the semen has been performed by a laboratory technician looking through a microscope and manually counting sperm. It was completely arbitrary as to what was differentiated a fast moving sperm from a sperm with medium velocity or a slow moving sperm. Studies showed that different technicians would sometimes come up with very different numbers for such things as sperm counts or sperm motility.
At IVF 1, we use a sophisticated electronic imaging system to visualize the sperm and a sophisticated software program to evaluate dozens of individual sperm parameters. This is sometimes referred to as CAST or computerized semen test.
As noted above, a standard or manual semen test will give only a few parameters. A computerized semen test will give many more parameters that are useful to the fertility specialist. Learn about the measurements of sperm motility.
Semen test with sperm motility analysis
The determination of the number of sperm that are moving rapidly in a forward progressive manner is of paramount importance in the evaluation of male fertility.
In an average semen test, there will be some sperm with no movement, some that are moving slowly and/or some that do not move in a forward direction. These sperm are less likely to be able to produce a pregnancy easily.
With a computerized semen test, the computer identifies and tracks every sperm seen in under the microscopic field. Over a fraction of a second, the path the sperm has traveled is analyzed and many different parameters can then be computed with a high degree of accuracy.
In the picture below, the squiggly green lines are the paths of individual sperm. The red dots mark sperm that are not moving.
Some of the parameters that are calculated include:
- Overall motility-Percent of sperm showing any movement
- Rapid motility-Percent of sperm traveling at a speed of 25 um/sec or faster
- Linearity-Percent of sperm moving in a straight line path
- Progressive motility-Percent of sperm moving rapidly AND in a straight path
- Mean velocities-An average speed for all sperm in the field of view
- Amplitude of lateral head displacement-The average distance that the sperm head “wiggles” back and forth while moving
A computerized semen test will give many more parameters that are useful to the fertility specialist. Learn about the measurements of sperm motility.
Here is what a sample report looks like:
Medical studies have evaluated these parameters individually and have found that many are independent predictors for male fertility. In other words, it is now possible to identify men with fertility problems even though their standard semen test may seem completely normal.
Sperm test for morphology
The appearance of sperm under a microscope is used as a sperm test. All men, in a semen specimen, will have some sperm with a normal appearance and some with an abnormal appearance. In men with normal fertility, a certain percentage of the sperm will have a normal appearance.
Over the years, different criteria have been used to distinguish normal from abnormal sperm and different “cutoff” levels have been used for what is considered “normal”.
In the past, infertility specialists used criteria that were established by the World Health Organization (WHO). However, several recent studies found that the WHO criteria was not very good at distinguishing fertile men from infertile men.
For this reason, many of us have now switched to a different criteria known as the “Strict Morphology”. It has also been referred to by the name of the doctor who developed it, Thinus Kruger, and is often called the Kruger morphology.
The concept behind strict morphology as a male fertility test, as the name suggests, is to evaluate sperm much more closely than we had in the past and have a stricter determination for what is considered normal. For example, older criteria would consider a man normal if he had 30-50% normal sperm. A normal percentage under Kruger’s criteria is 14% normal.
A normal morphology assessment using the Kruger method correlates much more closely with male fertility and thus is a better male fertility test. Studies have even shown that the percentage of eggs that are fertilized during in vitro fertilization (IVF) correlate well with the percentage of normal sperm seen.
One problem that remained is that often the technicians performing this sperm test would not evaluate semen samples consistently. There was often great variation from one day to the next or from technician to technician.
For this reason, at IVF 1, we have opted to use a computerized system for determining morphology. The software, which measures individual sperm cell size and shapes, was developed and validated by Dr. Kruger. In fact, we continue to perform our quality assessment by exchanging slides with Dr. Kruger’s lab to make sure that we are always in concordance with the gold standard.
We can always be sure that no matter who is performing the semen test that the results are going to be consistent from day to day.
Other types of male fertility tests
Endocrine (Hormone) Evaluation: Normal sperm production and sexual function are dependent on a normal hormonal environment. An endocrine evaluation should be performed if a sperm test reveals:
- low sperm concentration
- low sperm motility
The male hormone evaluation includes measurement of
- Follicle stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Thyroid function
- Liver function
Additional Semen Tests
Many different semen tests have been evaluated over the years. These semen tests may have at one time been commonly used but currently are not thought to offer additional help in the evaluation of the infertile male. They are no longer considered to be part of the standard male fertility test.
- Antisperm antibodies
- Semen fructose – the absence of fructose, a sugar-like substance in the semen, means either the vas deferens are obstructed or that the seminal vesicles are absent.
- Peroxidase staining – differentiates white blood cells from immature sperm to assess for possible infection.
- Sperm penetration assay (Hamster egg penetration test)
- Human zona pellucida binding test – measures the ability of sperm to bind to the zona pellucida (outer covering) of the egg. This test is also called the hemizona assay.
- Sperm DNA fragmentation testing
Specialized Semen Tests
These tests may be useful in a small number of patients for under certain special circumstances
- Hypo-osmotic swelling test – assesses the sperm membrane for structural integrity.
- Semen culture – checks for bacteria that may cause genital infection.
Vital staining – determines numbers of living and dead sperm.
The importance of genetic evaluation in infertile males with severe oligospermia (sperm counts of less than 5 to 10 million per ejaculate) or nonobstructive azoospermia (absence of sperm in semen, not due to blockage) has recently been established.
These patients may have abnormalities in the number of chromosomes (karyotype) or abnormalities in the structure of the male chromosome (microdeletion of the Y-chromosome). Patients with azoospermia as a result of being born without two vas deferens frequently have a mutation of a gene responsible for the disease cystic fibrosis but do not have the disease itself.
No semen test can fully predict fertility. Not all of the tests discussed above are appropriate for every couple. The tests performed will depend upon the findings during your evaluation.