Semen analysis or semen analysis is one of the fundamental complementary tests in the study of the male factor. The semen analysis will give us an idea not only of the production of spermatozoa by the testicle but also of their quality and the function of the seminal vesicles and the prostate.
Two main types of characteristics are evaluated in a semen analysis:
- The macroscopic ones, which can be seen with the naked eye.
- The microscopic ones, for which we will need the use of a microscope.
Semen characteristics
There are five main macroscopic characteristics: volume, color, odor, pH and viscosity.
- Volume
The normal volume is between 2 and 6 ml and reflects the function of the seminal vesicles and also the permeability of the ejaculatory ducts. The volume will be lower if the size of the seminal vesicles is smaller than normal. If, on the other hand, there is an obstruction at the level of the ejaculatory ducts, the volume and concentration of the spermatozoa will also be lower.
When the semen volume is below 2 ml we speak of hypospermia (WHO, 1999). If there is no semen at all after ejaculation, we would be talking about aspermia. - Smell and color
As for the odor and color of semen, the odor of semen is straw-like due to its polyamine content and the opalescent gray color. If there is an infectious process in the seminal vesicles and prostate (vesiculo-prostatitis), the odor will be different from normal and the color will be more yellowish. If there is a hemorrhage at the level of the seminal tract, the color will obviously be reddish. - The pH
The pH of semen is usually alkaline. The normal amount is between 7.0 and 8.5 (WHO, 1999), in patients with cystic fibrosis the pH is usually below 7.0. - Viscosity
In terms of viscosity, semen usually takes 15 to 20 minutes to liquefy. If it takes longer than 60 minutes, it would be considered pathological. Viscosity is usually determined by measuring the elasticity or filency of the semen with a pipette. It is considered normal below 2 cm. It can also be measured by capillary flow.
Microscopic characteristics of semen include: sperm concentration, total sperm count (obtained by multiplying the concentration by the volume of semen), round cell concentration (which includes round spermatids, primary spermatocytes and leukocytes), and red blood cell concentration (which will be found in cases of hemorrhage).leukocyte concentration is determined by the myeloperoxidase test. It is considered normal when the concentration is below 1 million/ml (WHO, 1999). Sperm concentration is considered normal when it is above 20 million/ml (WHO, 1999). If it is below 20 million/ml we would speak of oligozoospermia. Within the oligozoospermia several subgroups can be included: if it is between 10 and 20 million/ml it is considered a moderate oligozoospermia. If it is below 5 million/ml it is considered a severe oligozoospermia, and if it is below 1 million/ml it is considered a cryptopzoospermia.
Another important characteristic of the semen analysis is the vitality or viability of the spermatozoa. This characteristic will allow us to know if the sperm membranes are intact or not. That is to say, if the membrane or “skin” of the spermatozoa has a cut or not. This is important to know, because if it is broken, not only the motility could be affected, but also the DNA could be affected, as well as the biochemical bore or acrosome that the spermatozoa carries in the anterior part of the head. Vitality is considered normal when more than 75% of the spermatozoa are viable; in other words, less than 25% of the spermatozoa have permeabilized membranes or holes (WHO, 1999). If the percentage of vitality is below 75% we speak of necrozoospermia.