American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

The PAS stain, or Periodic Acid-Schiff stain, is commonly used in histology to demonstrate polysaccharides and mucosubstances within tissues. This staining technique exploits the chemical properties of certain carbohydrates; when the staining procedure is carried out, polysaccharides—such as glycogen, mucins, and various glycoproteins—undergo oxidation by periodic acid, leading to the formation of aldehyde groups. These aldehydes then react with the Schiff reagent to produce a bright magenta color, effectively highlighting the presence of these carbohydrates.

Using the PAS stain, histotechnicians can identify structures like the basement membrane of blood vessels and the glycogen content in cells. This specificity makes it an invaluable tool for diagnosing various diseases, including fungal infections and certain types of cancer, where abnormal carbohydrate presence is noted.

While the other options refer to different staining methods or do not align well with the PAS stain's primary applications, understanding the correct function of the PAS stain underlines its importance in histological analysis and diagnosis.