Histotechnologist (HTL) Practice Test 2026 – Complete Exam Prep

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.