Answer: Leukocytes, predominantly polymorphonuclear leukocytes (PMN, neutrophils), are present in most human ejaculates (Tomlinson et al., 1993; Johanisson et al., 2000). They can sometimes be differentiated from spermatids and spermatocytes in a semen smear stained with the Papanicolaou procedure. Differentiation is based on differences in staining coloration, and on nuclear size and shape (Johanisson et al., 2000). Polymorphonuclear leukocytes can easily be confused morphologically with multinucleated spermatids, but stain a bluish colour, in contrast to the more pinkish colour of spermatids (Johanisson et al., 2000). Nuclear size may also help identification: monocyte nuclei exhibit a wide variation in size, from approximately 7 µm for lymphocytes to over 15 µm for macrophages. These sizes are only guidelines, since degeneration and division affect the size of the nucleus. There are several other techniques for quantifying the leukocyte population in semen. As peroxidase-positive granulocytes are the predominant form of leukocytes in semen, routine assay of peroxidase activity is useful as an initial screening technique (Wolff, 1995; Johanisson et al., 2000) / (WHO 5th ed. manual, p. 102).
The test can be useful in distinguishing polymorphonuclear leukocytes from multinucleated spermatids, which are peroxidase-free (Johanisson et al., 2000). (WHO 5th ed. manual, p. 103).
The total number of peroxidase-positive cells in the ejaculate may reflect the severity of an inflammatory condition (Wolff, 1995). This is obtained by multiplying the concentration of peroxidase-positive cells by the volume of the whole ejaculate. Excessive numbers of leukocytes in the ejaculate (leukocytospermia, pyospermia) may be associated with infection and poor sperm quality. Leukocyte-dependent damage to spermatozoa depends on the total leukocyte number in the ejaculate and the number of leukocytes relative to the number of spermatozoa. Leukocytes can impair sperm motility and DNA integrity through an oxidative attack. (WHO 5th ed. manual, p. 107).
Therefore distinguishing spermatids from WBCs during a semen analysis is of great clinical value. Using the QwikCheck Test Strips for WBC detection allows this differentiation, as this kit is specific for leukocyte (granulocyte) detection.