Seminogram is a complementary test used to assess semen quality. The parameters to be taken into account and their normal values have been defined by the World Health Organization (WHO). This is really important, because every correctly performed semen analysis will have the same parameters, measured in the same way. In this way, the different seminograms that a male may have performed in different centers throughout the world can be evaluated and compared with each other.
The parameters measured in the semenogram are as follows:
- Macroscopic parameters
- the appearance of the semen, the volume of the ejaculate, the pH and the time it takes for the semen to liquefy (change from its usual dense white appearance to a water-like liquid).
- Sperm concentration.
- the number of spermatozoa per ml of semen. This value should be at least 15 mill/ml. If the sperm concentration is lower than this limit, it is called oligospermia.
- Sperm motility
- number of motile spermatozoa in the semen sample. Sperm motility is usually expressed as a percentage of total spermatozoa. We speak of progressive motile spermatozoa (progressing, moving forward), non-progressive spermatozoa (moving but not progressing) and immotile spermatozoa (which may be alive or dead). The union of progressive and non-progressive spermatozoa (a+b) is used as a reference value. The sum of these percentages must be at least 40%. In addition, progressive motility must be at least 32%. Those samples that present a motility below the established parameters are diagnosed as asthenospermia.
- Percentage of normal forms
- it is very common for men to be surprised to find that very few sperm in their ejaculate are considered normal. This is actually a normal occurrence, typical of the human semen sample, in which values of 5-10% of sperm normality are absolutely normal. In fact, the WHO considers semen to be normal when it has at least 4% of its spermatozoa are normal. A low number of normal spermatozoa is called teratozoospermia.
In recent times, different technology has been developed to assess other parameters in the semen sample, so that it has been possible to determine that samples that we would have diagnosed as normal are not in fact normal. For this reason, some centers have generated advanced, extended seminograms, where other parameters are measured. Some of them are discussed below:
- in any sperm sample it is possible to find spermatozoa that are not useful to fertilize the egg, and therefore enter apoptosis. Thus, a spermatozoon destined to die, indistinguishable to a biologist from another one in full activity, could be selected to microinject an oocyte, with the result of this fertilization being suboptimal to say the least. At present, it is possible to detect apoptotic spermatozoa by flow cytometry, and in the event that their number is excessive, there are also techniques to separate these spermatozoa from the rest, so that they cannot be selected during fertilization in the laboratory.
- Sperm DNA fragmentation
- the main function of a sperm is to deliver its genetic load, its DNA, to the oocyte. To do so, it must go through many difficulties and in the process, this DNA could be damaged. In order to avoid this damage as much as possible, the DNA of a spermatozoon travels packaged by different proteins. A failure in their function would cause the DNA to be more exposed and lead to DNA damage. In general, the oocyte tends to repair sperm DNA damage, although the efficiency of the process will depend on the age of the oocyte. In any case, this can only occur when there is a basis for DNA strand repair, i.e. when the fragmentation is "single-stranded", and when the damage is not excessive. Today it is possible to measure the percentage of spermatozoa with fragmented DNA in a sample and there are treatments to improve this percentage if necessary or to select non-fragmented spermatozoa.