Which statement describes a valid control approach for glycogen PAS staining in relation to diastase treatment?

• A. In a glycogen PAS test, diastase is used to digest glycogen in one control section to demonstrate loss of staining
• B. Diastase is used to enhance glycogen staining in all controls
• C. Diastase is used to fix glycogen in tissue sections
• D. Diastase is used to stain mucins in controls

Answer: (A)

Using diastase digestion as a control in glycogen PAS staining allows you to confirm that the staining you see is specifically due to glycogen. In this approach, one section is treated with diastase to digest glycogen before performing the PAS reaction. If the staining disappears or is significantly reduced after diastase treatment, it shows that the original PAS positivity depended on glycogen. This control helps distinguish glycogen from other PAS-positive substances, like mucins, which are not digested by diastase and would remain stained in a PAS–diastase result.