American Society for Clinical Pathology (ASCP) Histotechnologist Practice Test

Which fixative should not be used with Schiff reagent techniques?

1. Acetic acid

2. Glutaraldehyde

3. Glyoxal

4. Zinc salts

The correct answer is: Glyoxal

The correct choice indicates that glyoxal is a fixative that should not be used with Schiff reagent techniques. Glyoxal can interfere with the performance of the Schiff reagent because it reacts with aldehyde groups, potentially leading to false results or poor staining quality. Schiff reagent is primarily used for staining structures containing aldehyde groups, such as those present in carbohydrates, specifically in the detection of mucins or glycogen. When glyoxal is used as a fixative, it alters the chemical structure of these substances, making them less detectable by the Schiff reagent. In contrast, acetic acid, glutaraldehyde, and zinc salts do not disrupt the aldehyde interactions necessary for effective staining with the Schiff reagent. Each of these fixatives has properties that either stabilize cellular structures or preserve nucleic acids without significantly hindering the aldehyde functionality required for subsequent staining procedures. Therefore, they are compatible with methods that utilize Schiff reagent, while glyoxal's reactivity poses issues in this context.