Glycogen is best demonstrated by the use of which PAS method?

• A. PAS with diastase
• B. PAS without diastase
• C. PAS with and without diastase
• D. PAS staining without diastase

Answer: (C)

Glycogen is diastase-labile, so a true confirmation of its presence should involve showing what happens to PAS staining when glycogen is removed. The best approach is to compare PAS staining on a section stained without digestion to PAS staining on a section that has been digested with diastase and then restained. Glycogen-rich areas will be strongly positive on PAS before digestion but will lose staining after diastase digestion, whereas other PAS-positive substances (like certain mucopolysaccharides and basement membranes) are generally resistant to diastase and remain staining. By using both methods, you can confirm glycogen specifically rather than just any PAS-positive material.