What is the primary use of the Alkaline Congo Red Method?

• A. Demonstrate amyloid in tissues
• B. Demonstrate mucin
• C. Differentiate collagen
• D. Detect iron

Answer: (A)

Detecting amyloid deposits in tissue. The Congo red dye binds specifically to the beta-pleated sheet structure of amyloid, and using alkaline conditions enhances this interaction, giving a strong signal that is especially clear under polarized light where amyloid shows the characteristic apple-green birefringence. This makes the alkaline Congo red method the go-to stain for identifying amyloid.

The other options relate to different substances: mucin is demonstrated with stains like mucicarmine or Alcian blue, collagen with Masson's trichrome or Sirius red, and iron with Prussian blue.