Measuring the quality of sperm

These figures demonstrate that it is necessary to carry out examinations both on the woman and the man's sides.

1. Basic examinations

Semen analysis

The semen analysis is generally the first examination to be carried out on the man. This examination measures several parameters which characterise the sperm's fertilising ability: volume, viscosity, amount of spermatozoa per millilitre, motility of the spermatozoa, size and shape of the spermatozoa, doses of certain substances (zinc, fructose, carnitine, etc.).

The further the results of this examination diverge from the norm, the lower the fertility of the sperm is. The normal values for fertile sperm are summarised in the table below :

A semen analysis allows one to diagnose several problems in the fertilising capacity of the sperm. Among these are :

• Aspermia : the absence of sperm or volume of sperm < 0.5 ml
• Astheozoospermia : less than 50% of motile spermatozoa one hour after ejaculation
• Azoospermia : the absence of spermatozoa in the sperm
• Cryptozoospermia : invisible under the microscope but numbering between 10,000 and 100,000 in total
• Hypospermia : the total volume of ejaculated sperm < 2 ml
• Hyperspermia : the total volume of ejaculated sperm > 6 ml
• Leukospermia : number of leukocytes (white blood cells) > 1 million/ml
• Necrozoospermia : no living spermatozoa on ejaculation
• Oligospermia (Oligozoospermia) : number of spermatozoa < 20 million per ml or < 40 million in ejaculated sperm
• ligospermia">Severe oligospermia : number of spermatozoa < 5 million per ml
• pH : the potential of hydrogen, generally written "pH", is a measurement of acidityand must be between 6.5 and 8. If not, it means that there is a problem.
• Polyspermia ou polyzoospermia : number of spermatozoa > 200 million per ml
• Tératozoospermia : less than 30% normal spermatozoa
• Oligo-terato-astheno-spermia (OTA): a combination of oligospermia with an asthenospermia and a teratospermia.

DNA fragmentation test

This recently developed technique is less well-known and prescribed less often than the semen analysis. The DNA fragmentation test is nevertheless a decisive test that is complementary to the semen analysis. This test measures the state of the DNA of the spermatozoa. The head of the spermatozoon contains DNA, i.e. the individual's genetic material. Fragmentation signifies that some strands of DNA have been broken. If these breakages are not serious, then they will be repaired in the oocyte after fertilisation. However, above a certain level of breakages, this repair process is not possible at a sufficient level to allow the embryo to develop in a normal fashion. This deterioration of the DNA can be due to an excess of free radicals.

Standard values :

• <20% = good quality sperm DNA
• 20 - 30 % = heterogeneous sperm DNA
• > 30 % = very deteriorated sperm DNA

All too often, investigations on the man's side are limited to the semen analysis. However, a good semen analysis does not at all imply good DNA fragmentation. These two results are completely independent of each other. It is therefore recommended you ask to have a DNA fragmentation test as well as a semen analysis.

2. Detailed examinations

Depending on the results of these first tests, if necessary further examinations can be carried out. Some examples are :

• Sperm culture : examination for microbes in the sperm. This involves the direct examination under a microscope of a sperm sample, followed by its culturing on a suitable medium for growing bacteria.

• Seminal biochemistry : adding doses of different molecules if there is a lack of spermatozoa in the ejaculate fluid (carnithine, alpha-glucosidase, citric acid, acid phosphatase, zinc, fructose).

• Examination for anti-sperm antibodies. These tests are carried out on the spermatozoa, the seminal fluid and the blood. These tests are conducted if there is spermatozoa agglutination or anomalies in the spermatozoa's motility.

• Study of binding of spermatozoa to the pellucid zone : this involves observing the spermatozoa's ability to bind themselves onto the surface of the ovum.

• Study of the acrosome reaction : this involves evaluating the capacity of the spermatozoa to discharge the enzymes that enable the spermatozoa to penetrate the outer layer of the ovum.

• Hamster test :this measures the capacity of the sperm to penetrate the ovum. It is also used to measure the fertility of men who have a very low sperm count. It is systematically carried out as a screening test in many clinics before proceeding with in vitro fertilisation.

• Post-coital test: this evaluates not only factors on the woman's side but also the spermatozoa's capacity to penetrate the cervical mucus.