Along with the spermatozoa, there are other cells like immature germ cells, pus cells and leukocytes (WBC’s) present in the semen. These are very difficult to distinguish between in a wet mount and thus, these cells need to be stained for proper identification. Elevated levels of leukocytes are indicative of genital tract infections and result in an associated increase in ROS in the semen sample. The elevated ROS levels cause damage to the spermatozoa thus impairing their fertilization potential.
WBC's contain the peroxidase enzyme and the basis of this test is the staining and detection of peroxidase positive leukocytes.