Vital Staining of Sperm
During the examination of sperm for a semen analysis, the andrologist may see very few or no sperm moving. When this occurs, there is a staining procedure which determines if the non-motile sperm are alive or dead. This test is performed when the number of moving sperm is less than 5% because it is known that some sperm that are living do not have the capability to swim. This may be due to immaturity of the ejaculated sperm or to a functional defect in the tail or midpiece.
The staining procedure is performed with a small portion of the same sample that is given to the lab for the semen analysis. This small portion is combined with a drop of red stain on a slide. The living sperm will selectively block the stain from entering and remain white in appearance, while the dead sperm will absorb the stain and appear red because their outer membrane has lost the ability to selectively block the stain. A count of living and non-living sperm will be performed at that time and the result will be written as a percent of living sperm in the whole sample.
For example, one hundred sperm are counted from the semen sample. None of them are moving. A second drop of the semen sample is placed on another slide and a drop of the red, vital stain is added to it. Sixty sperm appear white or not stained. These sperm are living. Forty sperm appear red or stained. These sperm are dead. The vitality stain result is reported as 60% living. So, even though no sperm are moving, sixty percent of them are living. If we were using this sample to perform a sperm injection ICSI of the eggs, we would have sixty percent of the sperm available to inject into the eggs in order to fertilize them.
This can be a very important test for a couple and their physician who are trying to determine how best to approach their infertility.