Semen analysis
Encyclopedia
A semen analysis evaluates certain characteristics of a male's semen
and the sperm
contained in the semen. It may be done while investigating a couple's infertility
or after a vasectomy
to verify that the procedure was successful. It is also used for testing donors for sperm donation
, in stud farming and farm animal breeding
. Many men, especially if they are older, have a semen quality analysis, testing for common STIs, and perhaps testing for genetic defects done as part of routine pre-pregnancy testing, though this is decisively not the norm, as most doctors will not test the semen and sperm (and the man's genome and his STI status) unless specifically requested or there is a strong suspicion of a pathology in one of these areas discovered during the medical history or during the physical examination. Such testing, especially at that kind of comprehensive level, is very expensive and time-consuming, and may not be adequately covered by most insurance plans unless the insurance company, within the parameters of the plan and its coverage, accepts the medical evidence that there is a very valid reason for doing so.
. One source states that 30% of men with a normal semen analysis actually have abnormal sperm function. Conversely, men with poor semen analysis results may go on to father children.
, directing the sample into a clean cup.
A sample may also be collected during intercourse in a special type of condom
known as a collection condom. Collection condoms are made from silicone or polyurethane, as latex
is somewhat harmful to sperm. Many men prefer collection condoms to masturbation, and some religions prohibit masturbation entirely. Adherents of religions that prohibit contraception may use collection condoms with holes pricked in them.
A third option for collecting a sample is through coitus interruptus
(withdrawal). With this technique, the man removes his penis from his partner near the end of intercourse and ejaculates into a cup.
Finally, if a blockage in the vas deferens
is suspected to impede fertility, semen can be taken directly from the epididymis
. Such a collection is called per cutaneous epididymal sperm aspiration
(PESA). Alternatively, the testicular tissue itself, instead of the sperm produced can be investigated. Then, the collecting method is called TESE.
Sperm count, or sperm concentration to avoid mixup, measures the concentration of sperm in a man's ejaculate, distinguished from total sperm count, which is the sperm count multiplied with volume. Over 15 million sperm per milliliter is considered normal, according to the WHO in 2010. Older definitions state 20 million. A lower sperm count is considered oligozoospermia
. A vasectomy is considered successful if the sample is azoospermic
. Some define success with rare non-motile sperm are observed (fewer than 100,000 per millilitre). Others advocate obtaining a second semen analysis to verify the counts are not increasing (as can happen with re-canalization) and others still may perform a repeat vasectomy for this situation.
The average sperm count today is around 60 million per milliliter in the Western world, having decreased by 1-2% per year from a substantially higher number decades ago.
Chips for home use are emerging that can give an accurate estimation of sperm count after three samples taken on different days. Such a chip may measure the concentration of sperm in a semen sample against a control liquid filled with polystyrene beads.
, WebMD
defines normal motility as 60% of observed sperm, or at least 8 million per millilitre, showing good forward movement. The World Health Organization
has a similar value of 50% and this must be measured within 60 minutes of collection. WHO also has a parameter of vitality, with a lower reference limit of 60% live spermatozoa. A man can have a total number of sperm far over the limit of 20 million sperm cells per milliliter, but still have bad quality because too few of them are motile. However, if the sperm count is very high, then a low motility (for example, less than 60%) might not matter, because the fraction might still be more than 8 million per millilitre. The other way around, a man can have a sperm count far less than 20 million sperm cells per millilitre and still have good motility, if more than 60% of those observed sperm cells show good forward movement.
A more specified measure is motility grade, where the motility of sperm are divided into four different grades:
, the WHO criteria as described in 2010 state that a sample is normal (samples from men whose partners had a pregnancy in the last 12 months) if 4% (or 5th centile) or more of the observed sperm have normal morphology.
Morphology is a predictor of success in fertilizing oocytes during in vitro fertilization.
Up to 10% of all spermatozoa have observable defects and as such are disadvantaged in terms of fertilising an oocyte.
Also, sperm cells with tail-tip swelling patterns generally have lower frequency of aneuploidy
.
s, or that the man was born without seminal vesicles. In clinical practice, a volume of less than 2 mL in the setting of infertility and absent sperm should prompt an evaluation for obstructive azoospermia
. A caveat to this is be sure it has been at least 48 hours since the last ejaculation to time of sample collection.
in the semen, WebMD lists normal as at least 3 mg/mL. WHO specifies a normal level of 13 μmol
per sample. Absence of fructose may indicate a problem with the seminal vesicles.
range of 7.1-8.0; WHO criteria specify normal as 7.2-7.8. Acidic ejaculate (lower pH value) may indicate one or both of the seminal vesicles are blocked. A basic ejaculate (higher pH value) may indicate an infection
. A pH value outside of the normal range is harmful to sperm.
is the process when the gel formed by proteins from the seminal vesicles is broken up and the semen becomes more liquid. It normally takes less than 20 minutes for the sample to change from a thick gel
into a liquid
. An abnormally long liquefaction (more than 30 minutes at 37 24°C) time may indicate an infection. In the NICE
guidelines, a liquefaction time within 60 minutes is regarded as within normal ranges.
With a straw or a vial volume of 0.5 milliliter, the general guideline is that, for intracervical insemination (ICI), straws or vials making a total of 20 million motile spermatozoa in total is recommended. This is equal to 8 straws or vials 0.5 ml with MOT5, or 2 straws or vials of MOT20. For intrauterine insemination (IUI), 1-2 MOT5 straws or vials is regarded sufficient. In WHO terms, it is thus recommended to use approximately 20 million grade a+b sperm in ICI, and 2 million grade a+b in IUI.
Use of approximately 20 million sperm of motility grade c or d in ICI, and 5 million ones in IUI may be an approximate recommendation.
The sample may also be tested for white blood cell
s. A high level of white blood cells (over 1 million per milliliter) may indicate an infection.
itself, there are various methodological factors that may influence the results, giving rise to inter-method variation.
Compared to samples obtained from masturbation, semen samples from collection condoms have higher total sperm counts, sperm motility, and percentage of sperm with normal morphology. For this reason, they are believed to give more accurate results when used for semen analysis.
If the results from a man's first sample are subfertile, they must be verified with at least two more analyses. At least 2 to 4 weeks must be allowed between each analysis. Results for a single man may have a large amount of natural variation over time, meaning a single sample may not be representative of a man's average semen characteristics. In addition, sperm physiologist Joanna Ellington believes that the stress of producing an ejaculate sample for examination, often in an unfamiliar setting and without any lubrication (most lubricants are somewhat harmful to sperm), may explain why men's first samples often show poor results while later samples show normal results.
A man may prefer to produce his sample at home rather than at the clinic. The site of semen collection does not affect the results of a semen analysis.
Computer Assisted Semen Analysis (CASA) is a catch-all phrase for automatic or semi-automatic semen analysis techniques. Most systems are based on image analysis
, but alternative methods exist such as tracking cell movement on a digitizing tablet. Computer-assisted techniques are most-often used for the assessment of sperm concentration and mobility characteristics, such as velocity
and linear velocity. Nowadays, there are CASA systems, based on image analysis and using new techniques, with near perfect results, and doing full analysis in a few seconds. With some techniques, sperm concentration and motility measurements are at least as reliable as current manual methods.
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...
and the sperm
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
contained in the semen. It may be done while investigating a couple's infertility
Infertility
Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...
or after a vasectomy
Vasectomy
Vasectomy is a surgical procedure for male sterilization and/or permanent birth control. During the procedure, the vasa deferentia of a man are severed, and then tied/sealed in a manner such to prevent sperm from entering into the seminal stream...
to verify that the procedure was successful. It is also used for testing donors for sperm donation
Sperm donation
Sperm donation is the provision by a man, , of his sperm, with the intention that it be used to impregnate a woman who is not usually the man's sexual partner, in order to produce a child....
, in stud farming and farm animal breeding
Animal breeding
Animal breeding is a branch of animal science that addresses the evaluation of the genetic value of domestic livestock...
. Many men, especially if they are older, have a semen quality analysis, testing for common STIs, and perhaps testing for genetic defects done as part of routine pre-pregnancy testing, though this is decisively not the norm, as most doctors will not test the semen and sperm (and the man's genome and his STI status) unless specifically requested or there is a strong suspicion of a pathology in one of these areas discovered during the medical history or during the physical examination. Such testing, especially at that kind of comprehensive level, is very expensive and time-consuming, and may not be adequately covered by most insurance plans unless the insurance company, within the parameters of the plan and its coverage, accepts the medical evidence that there is a very valid reason for doing so.
Relation to fertility
The characteristics measured by semen analysis are only some of the factors in semen qualitySemen quality
Semen quality is a measure of the ability of semen to accomplish fertilization. Thus, it is a measure of fertility in a man. It is the sperm in the semen that are of importance, and therefore semen quality involves both sperm quantity and quality...
. One source states that 30% of men with a normal semen analysis actually have abnormal sperm function. Conversely, men with poor semen analysis results may go on to father children.
Collection methods
The most common way to collect a semen sample is through masturbationMasturbation
Masturbation refers to sexual stimulation of a person's own genitals, usually to the point of orgasm. The stimulation can be performed manually, by use of objects or tools, or by some combination of these methods. Masturbation is a common form of autoeroticism...
, directing the sample into a clean cup.
A sample may also be collected during intercourse in a special type of condom
Condom
A condom is a barrier device most commonly used during sexual intercourse to reduce the probability of pregnancy and spreading sexually transmitted diseases . It is put on a man's erect penis and physically blocks ejaculated semen from entering the body of a sexual partner...
known as a collection condom. Collection condoms are made from silicone or polyurethane, as latex
Latex
Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...
is somewhat harmful to sperm. Many men prefer collection condoms to masturbation, and some religions prohibit masturbation entirely. Adherents of religions that prohibit contraception may use collection condoms with holes pricked in them.
A third option for collecting a sample is through coitus interruptus
Coitus interruptus
Coitus interruptus, also known as the rejected sexual intercourse, withdrawal or pull-out method, is a method of birth-control in which a man, during intercourse withdraws his penis from a woman's vagina prior to ejaculation...
(withdrawal). With this technique, the man removes his penis from his partner near the end of intercourse and ejaculates into a cup.
Finally, if a blockage in the vas deferens
Vas deferens
The vas deferens , also called ductus deferens, , is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation....
is suspected to impede fertility, semen can be taken directly from the epididymis
Epididymis
The epididymis is part of the male reproductive system and is present in all male amniotes. It is a narrow, tightly-coiled tube connecting the efferent ducts from the rear of each testicle to its vas deferens. A similar, but probably non-homologous, structure is found in cartilaginous...
. Such a collection is called per cutaneous epididymal sperm aspiration
Per cutaneous Epididymal Sperm Aspiration
Percutaneous epididymal sperm aspiration is a technique used to determine sperm counts in the event of a possible blockage of the vas deferens. A small needle is inserted through the skin of the scrotum to collect sperm from the epididymis, where sperm are usually stored after production in the...
(PESA). Alternatively, the testicular tissue itself, instead of the sperm produced can be investigated. Then, the collecting method is called TESE.
Parameters
Examples of parameters measured in a semen analysis are: sperm count, motility, morphology, volume, fructose level and pH.Sperm count
Oligospermia
Oligospermia, also oligozoospermia, refers to semen with a low concentration of sperm and is a common finding in male infertility. Often semen with a decreased sperm concentration may also show significant abnormalities in sperm morphology and motility...
. A vasectomy is considered successful if the sample is azoospermic
Azoospermia
Azoospermia is the medical condition of a male not having any measurable level of sperm in his semen. It is associated with very low levels of fertility or even sterility, but many forms are amenable to medical treatment...
. Some define success with rare non-motile sperm are observed (fewer than 100,000 per millilitre). Others advocate obtaining a second semen analysis to verify the counts are not increasing (as can happen with re-canalization) and others still may perform a repeat vasectomy for this situation.
The average sperm count today is around 60 million per milliliter in the Western world, having decreased by 1-2% per year from a substantially higher number decades ago.
Chips for home use are emerging that can give an accurate estimation of sperm count after three samples taken on different days. Such a chip may measure the concentration of sperm in a semen sample against a control liquid filled with polystyrene beads.
Total sperm count
Total sperm count, or total sperm number, is the total number of spermatozoa in the entire ejaculate. By WHO, lower reference limit (2.5th percentile) is 39 million per ejaculate.Motility
Regarding sperm motilityMotility
Motility is a biological term which refers to the ability to move spontaneously and actively, consuming energy in the process. Most animals are motile but the term applies to single-celled and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in...
, WebMD
WebMD
WebMD is an American corporation which provides health information services. It was founded in 1996 by Jim Clark and Pavan Nigam as Healthscape, later Healtheon, and then acquired WebMD in 1999 to form Healtheon/WebMD...
defines normal motility as 60% of observed sperm, or at least 8 million per millilitre, showing good forward movement. The World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
has a similar value of 50% and this must be measured within 60 minutes of collection. WHO also has a parameter of vitality, with a lower reference limit of 60% live spermatozoa. A man can have a total number of sperm far over the limit of 20 million sperm cells per milliliter, but still have bad quality because too few of them are motile. However, if the sperm count is very high, then a low motility (for example, less than 60%) might not matter, because the fraction might still be more than 8 million per millilitre. The other way around, a man can have a sperm count far less than 20 million sperm cells per millilitre and still have good motility, if more than 60% of those observed sperm cells show good forward movement.
A more specified measure is motility grade, where the motility of sperm are divided into four different grades:
- Grade a: Sperm with progressive motility. These are the strongest and swim fast in a straight line. Sometimes it is also denoted motility I.
- Grade b: (non-linear motility): These also move forward but tend to travel in a curved or crooked motion. Sometimes also denoted motility II.
- Grade c: These have non-progressive motility because they do not move forward despite the fact that they move their tails. Sometimes also denoted motility III.
- Grade d: These are immotile and fail to move at all. Sometimes also denoted motility IV.
Morphology
Regarding sperm morphologyMorphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
, the WHO criteria as described in 2010 state that a sample is normal (samples from men whose partners had a pregnancy in the last 12 months) if 4% (or 5th centile) or more of the observed sperm have normal morphology.
Morphology is a predictor of success in fertilizing oocytes during in vitro fertilization.
Up to 10% of all spermatozoa have observable defects and as such are disadvantaged in terms of fertilising an oocyte.
Also, sperm cells with tail-tip swelling patterns generally have lower frequency of aneuploidy
Aneuploidy
Aneuploidy is an abnormal number of chromosomes, and is a type of chromosome abnormality. An extra or missing chromosome is a common cause of genetic disorders . Some cancer cells also have abnormal numbers of chromosomes. Aneuploidy occurs during cell division when the chromosomes do not separate...
.
Volume
WebMD advises that semen volumes between 1.0 mL and 6.5 mL are normal; WHO regards 1.5 ml as the lower reference limit. Low volume may indicate partial or complete blockage of the seminal vesicleSeminal vesicle
The seminal vesicles or vesicular glands are a pair of simple tubular glands posteroinferior to the urinary bladder of male mammals...
s, or that the man was born without seminal vesicles. In clinical practice, a volume of less than 2 mL in the setting of infertility and absent sperm should prompt an evaluation for obstructive azoospermia
Azoospermia
Azoospermia is the medical condition of a male not having any measurable level of sperm in his semen. It is associated with very low levels of fertility or even sterility, but many forms are amenable to medical treatment...
. A caveat to this is be sure it has been at least 48 hours since the last ejaculation to time of sample collection.
Fructose level
Regarding the level of fructoseFructose
Fructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...
in the semen, WebMD lists normal as at least 3 mg/mL. WHO specifies a normal level of 13 μmol
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
per sample. Absence of fructose may indicate a problem with the seminal vesicles.
pH
WebMD lists a normal pHPH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
range of 7.1-8.0; WHO criteria specify normal as 7.2-7.8. Acidic ejaculate (lower pH value) may indicate one or both of the seminal vesicles are blocked. A basic ejaculate (higher pH value) may indicate an infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
. A pH value outside of the normal range is harmful to sperm.
Liquefaction
The liquefactionLiquification
In physics, to liquefy means to turn something into the liquid state.-In Geology:In geology, liquefaction refers to the process by which saturated, unconsolidated sediments are transformed into a substance that acts like a liquid.Earthquakes can cause soil liquefaction where loosely packed,...
is the process when the gel formed by proteins from the seminal vesicles is broken up and the semen becomes more liquid. It normally takes less than 20 minutes for the sample to change from a thick gel
Gel
A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...
into a liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
. An abnormally long liquefaction (more than 30 minutes at 37 24°C) time may indicate an infection. In the NICE
National Institute for Health and Clinical Excellence
The National Institute for Health and Clinical Excellence is a special health authority of the English National Health Service , serving both English NHS and the Welsh NHS...
guidelines, a liquefaction time within 60 minutes is regarded as within normal ranges.
MOT
MOT is a measure of how many million sperm cells per ml are highly motile, that is, approximately of grade a (>25 micrometer per 5 sek. at room temperature) and grade b (>25 micrometer per 25 sek. at room temperature). Thus, it is a combination of sperm count and motility.With a straw or a vial volume of 0.5 milliliter, the general guideline is that, for intracervical insemination (ICI), straws or vials making a total of 20 million motile spermatozoa in total is recommended. This is equal to 8 straws or vials 0.5 ml with MOT5, or 2 straws or vials of MOT20. For intrauterine insemination (IUI), 1-2 MOT5 straws or vials is regarded sufficient. In WHO terms, it is thus recommended to use approximately 20 million grade a+b sperm in ICI, and 2 million grade a+b in IUI.
Total motile spermatozoa
Total motile spermatozoa (TMS) or total motile sperm count (TMSC) is a combination of sperm count, motility and volume, measuring how many million sperm cells in an entire ejaculate are motile.Use of approximately 20 million sperm of motility grade c or d in ICI, and 5 million ones in IUI may be an approximate recommendation.
Others
The NICE guidelines also include testing vitality, with normal ranges defined as more than 75% of sperm cells alive.The sample may also be tested for white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
s. A high level of white blood cells (over 1 million per milliliter) may indicate an infection.
Abnormalities
- AspermiaAspermiaAspermia is the complete lack of semen . Naturally, it is associated with infertility....
: absence of semen - AzoospermiaAzoospermiaAzoospermia is the medical condition of a male not having any measurable level of sperm in his semen. It is associated with very low levels of fertility or even sterility, but many forms are amenable to medical treatment...
: absence of sperm - HypospermiaHypospermiaHypospermia is the medical term when a man has an unusually low ejaculate volume, it is the logical opposite of Hyperspermia. It should not be confused with Oligospermia, which means low sperm count....
: low semen volume - Oligozoospermia: low sperm count
- AsthenozoospermiaAsthenozoospermiaAsthenozoospermia is the medical term for reduced sperm motility. Complete asthenozoospermia, that is, 100% immotile spermatozoa in the ejaculate, is reported at a frequency of 1 of 5000 men...
: poor sperm motility - Teratozoospermia: sperm carry more morphological defects than usual
Factors that influence results
Apart from the semen qualitySemen quality
Semen quality is a measure of the ability of semen to accomplish fertilization. Thus, it is a measure of fertility in a man. It is the sperm in the semen that are of importance, and therefore semen quality involves both sperm quantity and quality...
itself, there are various methodological factors that may influence the results, giving rise to inter-method variation.
Compared to samples obtained from masturbation, semen samples from collection condoms have higher total sperm counts, sperm motility, and percentage of sperm with normal morphology. For this reason, they are believed to give more accurate results when used for semen analysis.
If the results from a man's first sample are subfertile, they must be verified with at least two more analyses. At least 2 to 4 weeks must be allowed between each analysis. Results for a single man may have a large amount of natural variation over time, meaning a single sample may not be representative of a man's average semen characteristics. In addition, sperm physiologist Joanna Ellington believes that the stress of producing an ejaculate sample for examination, often in an unfamiliar setting and without any lubrication (most lubricants are somewhat harmful to sperm), may explain why men's first samples often show poor results while later samples show normal results.
A man may prefer to produce his sample at home rather than at the clinic. The site of semen collection does not affect the results of a semen analysis.
Measurement methods
Volume can be determined by measuring the weight of the sample container, knowing the mass of the empty container. Sperm count and morphology can be calculated by microscopy. Sperm count can also be estimated by kits that measure the amount of a sperm-associated protein, and are suitable for home use.Computer Assisted Semen Analysis (CASA) is a catch-all phrase for automatic or semi-automatic semen analysis techniques. Most systems are based on image analysis
Image analysis
Image analysis is the extraction of meaningful information from images; mainly from digital images by means of digital image processing techniques...
, but alternative methods exist such as tracking cell movement on a digitizing tablet. Computer-assisted techniques are most-often used for the assessment of sperm concentration and mobility characteristics, such as velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
and linear velocity. Nowadays, there are CASA systems, based on image analysis and using new techniques, with near perfect results, and doing full analysis in a few seconds. With some techniques, sperm concentration and motility measurements are at least as reliable as current manual methods.
See also
- Semen qualitySemen qualitySemen quality is a measure of the ability of semen to accomplish fertilization. Thus, it is a measure of fertility in a man. It is the sperm in the semen that are of importance, and therefore semen quality involves both sperm quantity and quality...
- Artificial inseminationArtificial inseminationArtificial insemination, or AI, is the process by which sperm is placed into the reproductive tract of a female for the purpose of impregnating the female by using means other than sexual intercourse or natural insemination...
for more details of how semen parameters affects pregnancy rate
External links
- Geneva Foundation for Medical Education and Research - complete list of parameters.