American Society for Clinical Pathology (ASCP) Histotechnologist Practice Test

Which method is best used to demonstrate amyloid in tissue?

1. Alkaline Congo red method

2. Masson's trichrome

3. Sirius red stain

4. Periodic acid-Schiff reaction

The correct answer is: Alkaline Congo red method

The alkaline Congo red method is the preferred technique for demonstrating amyloid in tissue due to its high specificity and sensitivity for amyloid deposits. When tissue sections are stained with Congo red dye and viewed under polarized light, amyloid deposits exhibit a characteristic apple-green birefringence. This unique property is crucial for differentiating amyloid from other deposits, as it provides a definitive visual verification of amyloid presence. The other methods listed, while useful for other purposes in histology, do not specifically target amyloid. Masson's trichrome stain is primarily used to highlight collagen and muscle fibers, and while it can provide color contrast in tissue morphology, it lacks the specificity needed for amyloid identification. The Sirius red stain can detect amyloid as well, but it is primarily employed to highlight collagen structures and may not provide the same level of distinction as alkaline Congo red under polarized light. The Periodic acid-Schiff reaction is used predominantly to highlight polysaccharides and certain glycoproteins, making it unsuitable for amyloid detection in tissues. Thus, the alkaline Congo red method remains the most effective choice for identifying amyloid in histological samples.