Quality control for PAS glycogen stains requires how many control sections and what should they contain?

• A. Two control sections of liver containing glycogen, one with diastase and one without
• B. Three control sections of liver with varying glycogen
• C. One control section of kidney with glycogen
• D. Four control sections of brain without glycogen

Answer: (A)

Glycogen-specific quality control for PAS staining uses two liver sections containing glycogen: one that is stained without enzyme digestion and one that is pre-digested with diastase. The un-digested section should show the magenta PAS response because glycogen is present. The section treated with diastase should lose the glycogen and therefore lose the PAS staining, demonstrating that the signal in the unstained control came from glycogen specifically and not from other PAS-positive materials. Liver is chosen because it stores abundant glycogen, making the positive control robust. Using other tissues or more sections wouldn’t provide the needed confirmation of both presence and specificity.