Which staining approach confirms amyloid detection using polarized light?

• A. Congo red on polarized light
• B. Congo red under bright-field
• C. Congo red with fluorescence
• D. Congo red with heat

Answer: (A)

Amyloid detection is confirmed by Congo red staining viewed under polarized light, which reveals apple-green birefringence. The dye binds specifically to the cross-beta structure of amyloid fibrils; when the stained section is examined with polarized light, the interaction between the dye and the aligned fibrils causes a distinct green birefringent signal that is diagnostic. Viewing the stained tissue under bright-field won’t show this birefringence, fluorescence would require a different visualization method and doesn’t rely on polarized light, and heating does not induce the diagnostic optical property. So, Congo red on polarized light is the approach that confirms amyloid.