Which control slide is used to assess glycogen storage in liver tissue?

• A. PAS glycogen
• B. Oil Red O
• C. Verhoeff's Van Gieson
• D. Perl's Prussian Blue

Answer: (A)

Glycogen storage is detected using the periodic acid–Schiff (PAS) reaction, which stains glycogen magenta. A control slide prepared with a known glycogen-containing material and stained with PAS—often labeled as a PAS glycogen control—provides a positive reference to verify that the staining and processing are working correctly and that glycogen can be seen as expected in liver tissue. The other stains serve different purposes: Oil Red O targets lipids in frozen sections, Verhoeff's Van Gieson highlights elastic fibers, and Perl's Prussian Blue detects iron deposits. So the PAS glycogen control slide is the appropriate choice because it directly confirms glycogen presence.