SPERM VITALITY TEST – WHICH PATIENTS COULD BENEFIT FROM IT?
A sperm vitality test shows what percentage of the spermatozoa in the sample are vital (alive). Patients are usually referred for this test after a low percentage of sperm motility is detected on semen analysis. The results of the sperm vitality test give important information to the treating urologist about diagnosing and treating the possible cause of infertility.
The sperm vitality test is also an important tool when a couple with male factor infertility is about to undergo an IVF procedure. The oocytes of these couples are fertilized by IntraCytoplasmic Sperm Injection (ICSI). During ICSI the embryologist selects a single spermatozoa and injects it in one oocyte. As a rule the spermatozoa selected are always with the best available motility and morphology. In cases of very low or no motility, sperm vitality test is used to select viable spermatozoa, since only they can fertilize oocytes.
There are different types of vitality tests. The 2 most commonly used are the Hypo-osmotic Swelling (HOS) test and the Eosin Nigrosin test.
The advantage of the HOS test is that spermatozoa are still alive and can be used for ICSI following the test. During the test spermatozoa are put in hypo-osmotic solution (i.e. in solution with lower concentration of solutes compared to the inside of the spermatozoa). Due to osmosis, water starts coming into the spermatozoa and if their membrane is functional (i.e. if they are alive), their tails start swelling and curling. This process is completely reversible and those spermatozoa can be used for ICSI after they are washed.
The Eosin Nigrosin test also distinguishes between viable and non-viable spermatozoa on the basis of their membrane integrity. Viable sperm do not let the red dye eosin penetrate their membrane and thus remain white, while non-viable sperm turn red. Nigrosin is a dark dye which improves contrast and makes it easier to distinguish viable and non-viable spermatozoa. The Eosin Nigrosin is often preferred for diagnostic purposes, as it is faster than the HOS test. However, sperm cannot be used for ICSI afterwards.
According to the World Health Organization (WHO) the reference value for sperm vitality is 58%. If less than 58% of your spermatozoa/those of your partner are non-viable, it is strongly recommended to consult with a urologist, specializing in fertility issues.