What is a semen analysis?
A semen analysis is a simple non invasive diagnostic test to evaluate male fertility and is one of the first investigations for an infertile couple. Male factor infertility due to abnormalities in sperm production or function accounts for 35 – 50% of all infertility cases. (1)
A semen analysis can also be performed following a vasectomy or vasectomy reversal for confirmation of the effectiveness of the procedure.
How is a semen analysis performed?
A semen sample is collected by masturbation and the ejaculate is collected into a container provided by the laboratory that is sterile and non toxic to spermatozoa. The container is clearly labelled with the patient details.
- Abstain from sex for a period of between 2 to 7 days. (2)
- Production of the specimen at the clinic performing the semen analysis to control the time between production and analysis. This will minimise exposure to any temperature and environmental fluctuations which could affect the results.
The sperm test
On receipt of the semen sample our highly-trained laboratory personnel will analyse the sample using a microscope to look at the appearance of the sample and compare it to the WHO reference values below.
World Health Organisation Reference values for semen analysis 2010:
|Parameter||WHO Lower Reference Value|
|Agglutination / MAR Binding||<50%|
|Sperm Motility||40% motility withv 32% demonstrating progressive motility|
|Sperm Concentration||15 million|
|Morphology||4% Normal forms|
Semen is composed of secretions from the seminal vesicles and prostate gland with a contribution from the bulbourethral glands and epididymides. The first fraction of the ejaculate contains the prostatic fluids which are rich in sperm. For this reason, if any of the ejaculate in particular the first portion is not collected, the laboratory personnel must be informed as this will affect the semen analysis result.
Viscosity and liquefaction
Viscosity is the fluidity of the sample. A viscous sample can be very sticky and adhere to the specimen container. A freshly collected semen sample is observed as a semi solid mass which gradually liquefies into a free flowing liquid. A highly viscous sample or incomplete liquefaction can interfere with the accurate assessment of sperm motility and concentration. Inadequate liquefaction can indicate a deficiency of prostatic enzymes.
Under microscopic examination, sperm should be freely swimming and not sticking to one another. 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 degree of agglutination is graded 1 – 4 as outlined in the table below. The presence of agglutination can be indicative of the presence of anti sperm antibodies whose presence can be determined using a MAR (Mixed antibody reaction) test.
Degree of agglutination:
Grade 1: Isolated with < 10 sperm per agglutinate
Grade 2: Moderate with 10 – 50 sperm per agglutinate
Grade 3: > 50 sperm per agglutinate
Grade 4: All sperm agglutinated and not freely swimming
The MAR test (Mixed agglutination reaction) can determine the presence of anti sperm bodies. Anti-sperm antibodies (ASAs) 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. Sperm in the testicles are protected from circulating antibodies by the blood testis barrier. A breach in this barrier (ie testicular trauma or a vasectomy) 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.
Sperm motility and progression
Motility refers to the movement of the sperm which is central to the fertilisation process. Sperm motility is the percentage of sperm swimming and can be affected by patient age, health, length of abstinence period and exposure to external influences i.e. toxins and excessive heat. Sperm progression is a subjective evaluation of the sperm movement ie how fast the sperm are swimming ie the ability of the sperm to swim towards the egg.
The motility of the sperm is categorized as:
|Non progressive motility||Moving but no forward progression (think of the
sperm as swimming in circles)
|Progressive Motility||Actively moving sperm|
Sperm concentration is the number of sperm per ml of semen. The lower reference limit for sperm concentration is 15 × 106 spermatozoa per ml. Sperm concentration is a predictor of conception and related to pregnancy rates (3,4)
Oligozoospermia is the term used to describe a sperm concentration of <15x106ml. Sperm concentrations can fluctuate and it is advisable to have two or three semen analysis reports to establish a baseline reading.
What happens if there are no sperm observed?
Azoospermia is characterised by the absence of sperm in the semen sample following centrifugation (a technique exerting a gravitational force on the specimen which drives 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 along with a medical investigation evaluating the testes and blood samples for hormone profiling for FSH (Follicle stimulating hormone), LH (Luteinizing hormone), testosterone and prolactin. 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).
Morphology refers to the physical appearance of the sperm ie whether the sperm are a normal 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. There is a direct link between sperm morphology and fertilisation potential.
Interpretation of the Results
Semen 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.
Azoospermia – No sperm present in the semen
Oligozoospermia – Low sperm count
Asthenozoospermia – Poor sperm motility
Teratozoospermia – High incidence of morphologically abnormal sperm
Andrology – male infertility – Herts and Essex FertilityHerts and Essex Fertility
Making an appointment for a semen analysis is quick, easy and strictly confidential, and you do not need a GP or hospital referral. Simply call us on 01992 78 50 60 or email firstname.lastname@example.org.
1: Gardner.D, Weissman.A, Howles.C and Shohan.Z (2009) Textbook of Assisted Reproductive
Technologies, Third edition, chapter 4, evaluation of sperm. Silverberg.K and Turner.T
2: WHO Laboratory manual for the examination and processing of human semen
5Th Edition 2011 (ISBN 978 92 4 154778 9)
3: Zinaman.M, Brown.C, Selevan.S and Clegg.E
Semen Quality and Human Fertility: A prospective Study with healthy couples
Journal of Andrology,2000, (21), 1, 145 – 153
4: Bonde JPE, Ernst E, Jensen TK, Hjollund NHI, Kolstad H, Henriksen
TB, Scheike T, Giwercman A, Olsen J and Skakkebæk NE. Relation between
semen quality and fertility: a population-based study of 430
lancet, 1998 (352) 1172 – 1177