Which fixative is associated with false-positive PAS staining?

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Multiple Choice

Which fixative is associated with false-positive PAS staining?

Explanation:
Periodic acid–Schiff staining relies on oxidizing carbohydrates to aldehydes and then binding those aldehydes with Schiff reagent to produce magenta. If aldehyde groups are already present in the tissue from the fixative, Schiff reagent can react with them too, giving color even when carbohydrates aren’t there—a false-positive result. Glutaraldehyde is a dialdehyde fixative that leaves many reactive aldehyde residues in the tissue, along with extensive cross-linking, so it frequently produces this non-specific, misleading PAS staining. Other fixatives do not introduce aldehyde residues to the same extent, so the risk of false-positive PAS is much lower with them.

Periodic acid–Schiff staining relies on oxidizing carbohydrates to aldehydes and then binding those aldehydes with Schiff reagent to produce magenta. If aldehyde groups are already present in the tissue from the fixative, Schiff reagent can react with them too, giving color even when carbohydrates aren’t there—a false-positive result. Glutaraldehyde is a dialdehyde fixative that leaves many reactive aldehyde residues in the tissue, along with extensive cross-linking, so it frequently produces this non-specific, misleading PAS staining. Other fixatives do not introduce aldehyde residues to the same extent, so the risk of false-positive PAS is much lower with them.

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