Dr Lucy Richardson, Laboratory Director at The Herts & Essex Fertility Centre
What is a semen analysis?
A semen analysis is a very important non-invasive diagnostic test used to evaluate male fertility and should be one of the first investigations for a couple having difficulty conceiving. Male factor infertility can be due to abnormalities in sperm production, sperm function, or both and accounts for 40-50% of all infertility cases. A semen analysis can also be performed to confirm the effectiveness of a vasectomy or a vasectomy reversal. A semen analysis is also necessary if you wish to become a sperm donor.
How is a semen analysis performed?
The male patient will be asked to produce a semen sample into a specialised container provided by the laboratory which is sterile and non-toxic to sperm. The container will be clearly labelled with the patient’s details. Ahead of this appointment, it is very important to abstain from ejaculation for three to five days. A shorter or longer period may affect the results of the test. We would also recommend producing the sample at the clinic to control the time between production and analysis to minimise any temperature or environmental fluctuations which could also affect the test results.
The sperm test
Our highly-trained and experienced laboratory personnel will initially analyse the appearance and physical properties of the semen sample before using a microscope to examine the sperm cells themselves in detail.
Seminal fluid is composed of secretions from the seminal vesicles, the prostate gland, the bulbourethral glands and epididymides. The first part of the ejaculate contains the prostatic fluids which are rich in sperm. For this reason, if any of the ejaculate is not collected it will affect the semen analysis result, especially if it’s the first fraction. Laboratory staff must be informed if this is the case. Normal ejaculatory volume is upwards of 1.5ml.
Liquefaction and Viscosity
When a semen sample is freshly collected, it will take the form of a semi-solid mass which becomes liquid, a free flowing fluid through a process known as liquefaction. Incomplete liquefaction may indicate a deficiency of prostatic enzymes. Viscosity describes the fluidity of the sample. A viscous sample will be sticky and may adhere to the sample pot. A sample with incomplete liquefaction or high degree of viscosity can affect the assessment of sperm concentration and motility.
Sperm Concentration and Total Sperm Number
Sperm concentration is the number of sperm cells per ml of seminal fluid produced. The lower reference limit for sperm concentration is 15 million sperm per ml of seminal fluid produced. Sperm concentration is a predictor of conception and related to pregnancy rates. A sperm sample with a concentration is less than 15 million per ml is termed oligozoospermic. Sperm concentrations can fluctuate and it is always advisable to have two or three samples tested to establish a baseline reading. The total sperm number is the number of sperm in the entire sample and can be calculated by multiplying sperm concentration with sample volume. A normal total sperm number is 39 million or above.
Total Sperm Motility and Progressive Motility
Motility describes the ability of sperm to swim which is pivotal to natural fertilisation. Motility is calculated as a percentage of swimming (motile) sperm compared to non-swimming (immotile sperm). Total sperm motility should be 40% or greater. Progressive motility is a subjective evaluation of the sperm movement used as a measure of how fast the sperm are swimming to measure their ability to swim towards the egg. Progressive motility is where the sperm are actively swimming. Non-progressive motility is where the sperm are moving but not travelling forwards. Immotile sperm do not swim. Sperm motility can be influenced by abstinence period, patient age and health and also external factors including toxins and excessive heat.
Morphology refers to the physical appearance of the sperm and whether the sperm are normal in shape. A morphologically normal sperm will have a smooth oval head with a single unbroken straight tail connected to the head with a straight mid piece. In a normal semen sample as many as 96% of the sperm are identified as abnormal, which in itself is completely normal! There is a direct link between sperm morphology and fertilisation potential and some sperm will not be able to fertilise an egg due to their shape.
In order to fertilise an egg, sperm should be swimming freely and not stuck to each other. Agglutination of sperm occurs when the head or tail of one sperm sticks to another sperm restricting the motility of the sperm. Severe agglutination can affect the assessment of sperm motility and concentration. The presence of agglutination can be indicative of the presence of anti-sperm antibodies whose presence can be determined using a MAR (Mixed Antiglobulin Reaction) test.
The MAR test can determine the presence of anti-sperm bodies (ASABs). ASABs in semen can cause the sperm to agglutinate together and impair the ability of the sperm to reach and bind to the outside of the egg. ASABs can arise following testicular trauma or surgery. Sperm in the testicles are protected from circulating antibodies by the blood-testis barrier. A breach in this barrier can lead to antibody formation and the secretion of antibodies into the accessory glands which form a large proportion of the seminal plasma. The result is clinically significant when greater than 50% of the sperm are bound.
Hyaluron Binding Assay
The Hyaluron Binding Assay (HBA test) is a highly specialised test to assess the proportion of mature sperm with the semen sample. Sperm maturity is important because only mature sperm can naturally fertilise an egg. Therefore if levels of mature sperm within the sample are low, this means there is a reduced number of sperm cells which have fertilisation potential. A normal HBA score would be upwards of 65%. Herts and Essex Fertility Centre include this highly specialised as standard within all of our semen assessments.
What happens if there are no sperm in the sample?
A sample with no sperm cells present is described as azoospermic. A sample is considered apparently azoospermic after the sample is processed by centrifugation, a technique which uses a gravitational force on the specimen to drive any sperm present in the sample into a pellet at the bottom of the test tube. A second semen analysis will be requested to confirm the diagnosis. To understand the potential cause of the azoospermia, a medical investigation evaluating the testes and blood sample for hormone profiling for FSH (Follicle stimulating hormone), LH (Luteinizing hormone), testosterone and prolactin will be recommended. Azoospermia can be due to inadequate stimulation of the testes, an obstruction of the post testicular genital tract or testicular failure. The diagnosis will determine eligibility for the surgical recovery of epididymal or testicular sperm to be used for ICSI (Intra Cytoplasmic Sperm Injection).
Interpretation of the Results
Semen sample results may exhibit natural variation over time, meaning a single semen sample may not be representative of a man’s average semen characteristics. The outcome of a semen assessment can be influenced by a variety of factors including lifestyle, testicular damage, and pharmaceutical agents. For this reason, it is not unusual to be asked for a repeat semen analysis.
Making an appointment for a semen analysis is quick, easy and strictly confidential, and you do not need a GP or hospital referral.