Glutaraldehyde is one of the recommended fixatives for the PAS reaction.

• A. True
• B. False
• C. It is recommended only for other stains
• D. It should be used with caution

Answer: (B)

Periodic acid–Schiff staining detects carbohydrates by oxidizing them to aldehydes that react with Schiff reagent. Fixation that masks carbohydrate residues or alters their chemical accessibility will blunt the reaction. Glutaraldehyde cross-links proteins very strongly, which can mask carbohydrate moieties and reduce the formation of aldehydes needed for the PAS reaction. Because of this, glutaraldehyde is not a recommended fixative for PAS; formalin-based fixatives or others that preserve carbohydrates without masking them are preferred.