|Handout on Interpreting the Semen Analysis|
A semen analysis is a specialized test which can provide valuable information on the fertility potential of males. It is also a requirement following vasectomy and vasectomy reversal to ensure technical success. It is important to understand how to collect a proper specimen. It is also important to understand the interpretation of a semen analysis result - and expecially the limitations of semen analysis in the evaluation of infertile males.
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Please be aware that Lifelabs and BC Biomed only accept semen specimens at specific times. The specialty labs at the reproductive medicine clinics require appointments to provide on-site samples.
* For every additional day up to about 7 days, the sperm concentration can increase about 25%. This makes comparison of results very difficult if different abstenance intervals are used. This effect is most pronounced for the first few days.
BC Biomedical: chose the letter 'S', then select 'semen analysis'
Lifelabs: you will need to call 1-855-412-4495 (7 am to 7 pm Monday to Friday) to book an appointment
Semen analysis (SA) should be interpreted in the context of the complete male and female evaluation - it should never be evaluated in isolation.
SEMEN ANALYSIS IS NOT A DIAGNOSTIC TEST WHICH CAN DIFFERENTATE FERTILE FROM INFERTILE MEN*
*With the sole exception of men with azospermia (no sperm)
This oft quoted but frequently ignored fundamental fact about semen analysis has lead to flawed interpretation of SA. It is inaccurate to simply state that the semen analysis, or any one particular semen analysis parameter for that matter, is either 'normal' or 'abnormal'. With the exception of men without sperm, there is always a possibility of conception so long as the partner is not sterile. By understanding this fundamental concept, the question "Is my semen analysis normal?" can then be appropriately restated as:
'How do my semen analysis results affect the chances that we will achieve a pregnancy over a given length of time?"
Putting your semen analysis in perspective involves consideration of:
While it is possible to make comment on the general chances of achieving a pregnancy for a man with specific semen analysis parameters with a standardized 'reference spouse' (i.e. an otherwise healthy woman between the ages of 20-30 with no prior pregnancy history and with no prior attempts at achieiving a pregnancy), this sort of assessment is not applicable to the majority of couples who are seen with fertility problems. An individualized assessment which takes into account male and female factors is always required.
Before reviewing what the implications of the different parameters are on the chances of conceiving, it is helpful to understand what is actually measured and what is involved with these measurement. The commonly measured parameters in routine semen analysis are:
NOTE: some laboratory requisitions inappropriately label the concentration as 'Total Sperm Count'. You can tell if this is the case by looking at the units - if the units are a 'number/volume', then it is a concentration. If the unit is just a 'number' then it is a total count. You can easily determine the total sperm count by multiplying the semen volume by the sperm concentration.
Any variation in the semen analysis report from measurement to measurement may result from 3 possible causes:
It is perfectly normal for there to be variation in these parameters from sample to sample within the same individual even if there has been absolutely no change in that persons intrinsice fertility potential. This is known as 'normal biological variation'. Just as no one wakes up the exact same every day, semen analyses parameters will vary from day to day also.
Measurement of these parameters is a human endeavor and therefore subject to error. This is known as 'laboratory error'. Most men ejaculate tens if not hundreds of millions of sperm. It is not currently possible (nor would it make any difference) to measure every single sperm in a sample. In fact, only a very small proportion of the sperm in a sample are assessed - much less than 1% of 1% of the sample. Out of 100 million sperm, only a few hundred are actually measured. Concentration, for example, is estimated by counting the number of sperm within a very small volume using a microcell counter. Based on the number of sperm within the known volume, the total number of sperm or a sperm concentration can be estimated. Because only a very small sample is measured, there is great potential for inaccuracy. For example, it has been demonstrated that if a pooled semen sample (i.e. collected from many men and mixed together) is sent to enough labs, that some of the labs will report that no sperm are present even though there are many millions of sperm present - just by chance the sample of fluid taken from the main sample will not have any sperm! Using a computer to do the measuring (CASA - computer aided semen analysis) provides only a modest benefit over using a human.
THE AVERAGE DEGREE OF VARIATION BETWEEN THE PARAMETERS ON ANY 2 SEPARATE SAMPLES (COVARIANCE) IN A MALE WHO IS HEALTHY AND HAS NOT HAD A CHANGE IN HIS FERTILITY STATUS IS TYPICALLY ABOUT 60%!
This is to say that there is a significant amount of normal biological variation and laboratory error built into the end results of any semen analysis report. As a result, great caution should be exercised when using semen analysis results to determine if there has been a significant change in a man's intrinsic fertility status or by inappropriately assigning a greater degree of precision and accuracy to a semen analysis report than is diagnostically achievable. (references: Keel et al Fertility and Sterility 2006; Carlsen et al Fertility and Sterility 2004)
Figure: This graph shows how the concentration in a single man naturally varies over time with several measurements. These are the normal 'ups and downs' found in sperm production and with lab variance. Despite the sometimes dramatic changes in concentration, this man's intrinsic fertility potential was unchanged. The take home message is not to get too excited by the changes seen between a couple of semen analysis reports. They are more likely the result of normal variation than an indicator of increased or decreased fertility potential. Consistent changes which trend either upwards or downwards are required before it can be stated if things are getting 'better or worse'.
It is impossible to use the semen analysis parameters to predict the chances of pregnancy without knowledge about the other factors that might impact a couples ability to conceive. Remeber, it always takes two. The one exception is in a man who has no sperm - even if nothing is known about his partner, it can be stated with certainty that they will not be able to conceive naturally unless he sperm appear in the ejaculate. For everyone else, the assessment is individualized. Having said that, some general comments can be made regarging semen analysis results in terms of the probability of conception - increased or decreased - regardless of what is happening with a man's partner.
Despite all of the parameters that are reported on a semen analysis report, the only parameters that have been proven to correlate with the chances of naturally achieving a pregnancy are:
Note that these factors apply to the chances of conceiving naturally and do not apply to using semen analysis to predict the success of ART such as intrauterine insemination or in vitro fertilization.
Problems with sperm morphology (how the sperm look) do have an impact on the chances of conception with intercourse, but the effect is relatively small. In fact, in men with high concentrations, the morphology does NOT appear to have any bearing on the chances of natural conception. Note that neither semen volume or motility have any impact on the chances of conception once concentration and morphology are taken into account. The question then becomes "At what point and to what degree do changes in morphology and concentration affect the chances of achieving a pregnancy?". As mentioned previously, this cannot be stated without knowing something about a man's partner. We can, however, make some comment on how the results of a semen analysis might affect the chances of natural conception under specific circumstances where other factors which can affect conception are known.
Figure: Concentration and Pregnancy. There are 3 things to note on this graph: (1) there is a marked increase in the chance of conception as the concentration approaches about 40 million/ml, (2) above and beyond a concentration of about 60 million/ml, there is no further increase in the chance of conception and (3) despite the fact that there is an association between concentration and the chance of conception up to about 40 million/ml, it is not until the concentration is much less than about 10 million/ml that there are lower than even odds of conception over the course of a year. Modified from Bonde et al. Relation between semen quality and fertility: a population-based study of 430 first pregnancy planners. Lancet 1998.
Figure: Morphology and Pregnancy. The main thing to note is that there is a gradual but small decreae in the probability of conception as morphology declines. It should be noted that the effect of morphology on the probability of conception is relatively minor compared to that of concentration. Modified from Bonde et al. Relation between semen quality and fertility: a population-based study of 430 first pregnancy planners. Lancet 1998. Specifically, the old WHO morphology criteria have been changed to the Kruger Strict criteria for illustrative purposes.
Very commonly, the only 'abnormality' on a semen analysis report will be the morphology - the concentration and all other parameters will be 'within reference range'. This is known as isolated teratospermia. Most patients are alarmed at this. While a decrease in morphology can be associated with a decreased probability of conception, this is one instance in which there is probably no effect on the chances of conception and the morphology can be safely ignored.
Figure: Difference in the significance of morphology depending on the sperm concentration. While there is a statistical trend towards an increased probability of pregnancy with increasing morphology, the effect is muted and probably clinically insignificant in men with normal sperm concentrations. Even for men with reduced sperm concentrations, the effect is minimal.
There is significantly less data on using semen analysis to predict pregnancy in infertile couples - which is a problem since this is the group we are most interested in. However, the chances for conception overall are quite favorable in couples labelled as 'infertile' during years 2 and 3, even if nothing is known about a man's semen analysis. Some semen analysis reports use reference ranges from a study published in the New England Journal of Medicine by Guzick et al in 2001 titled 'Sperm morphology, motility and concentration in fertile and infertile men'. This study used a 'case-control' design rather than a 'prospective cohort' design which did not account for the prevalence of the semen analysis parameters in the general infertile and fertile populations. The bottom line is that the study over-estimated by far the ability of various semen analysis parameters to distinguish men who will have difficulty conceiving from those who will not.
Taking some 'extreme' examples of semen analysis parameters will help put the probability of conception of infertile couples in perspective. (references: Collins et al Fertility and Sterility 1995; Snick et al. Human Reproduction 1997)
Example 1: Couples unable to conceive for 1 year. No major female factor identified. No prior fertility history. If the sperm concentration is <20 million/ml, 1 in 3 couples will conceive within 2 years of being declared infertile.
Example 2: Couples unable to conceive for 1 year. No major female factor identified. No prior fertility history. If the total motile count is <5 million/ml, 1 in 4 couples will conceive with 2 years of being declared 'infertile'.
UNLESS THE SPERM CONCENTRATION IS VERY, VERY LOW, THERE IS STILL A REASONABLE CHANCE THAT A COUPLE WILL BE ABLE TO CONCEIVE IN THE 2 YEARS AFTER THEY ARE DECLARED INFERTILE - THE PROBABILITY IS USUALLY GREATER THAN 1 IN 3
Hopefully this has helped you understand the role of semen analysis in couples attempting to achieve a pregnancy naturally. You can make an appointment with Dr. Poon if you have further questions regarding your particular scenario.
The 'reference ranges' published on semen analysis reports should be disregarded. The relationship between sperm concentration, morphology and the probability of conception is such that using a 'cutpoint' or 'lower limit' is too crude. Also, the distribution of all of the measured semen analysis parameters in the male population do not follow a bell-shaped distribution ('normal' in statistical parlance). As a result, calculated 'averages' have no clinical utility nor statistical meaning. Finally, the reference ranges are continually changing. Over the past several decades, the lower limit of what is considered 'acceptable' has continued to decrease. Most recently, the World Health Organization published revised reference ranges for semen analysis parameters in late 2010. 'Acceptable morphology' has decreased from ≥14% to ≥5% using the Kruger Strict criteria. Therefore men who were told they were 'abnormal' before would now be considered 'normal'. The approach taken by the WHO ignores the actual relationship between semen analysis results and conception.
The best way to approach interpretation of semen analysis parameters is not to state that they are 'normal' or 'abnormal' but instead to look at the parameters of importance (which will depend on the context in which the results are being applied) and determining what if any effect they will have on the probability of achieving a pregnancy - and also determining to what degree they will have that effect.
Author: K Poon; Major Revision February 2011