What aspect differentiates the PAS stain from the Gridley technique?

• A. Type of oxidizer used
• B. Stain color produced
• C. Counterstain used
• D. Specimen thickness required

Answer: (A)

The key difference lies in the reagent used to oxidize sugars before the color reaction. In the PAS reaction, a specific oxidizing agent (periodic acid) converts vicinal diols in carbohydrates into aldehyde groups, which then react with Schiff reagent to give the magenta color. The Gridley technique uses a different oxidizer for that oxidation step, so the chemical pathway and which structures are highlighted change. Because the oxidation step is what enables the subsequent Schiff reaction to reveal carbohydrates, the type of oxidizer used is what sets these methods apart.