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University revision · Cellular Pathology

Periodic Acid-Schiff (PAS) Technique

The Periodic Acid-Schiff (PAS) reaction is the cornerstone special stain for carbohydrates in histopathology, a mandatory topic in tertiary cellular pathology programs across Zambian colleges and universities. This module details the chemical principle: periodic acid oxidizes vicinal diols in sugar residues to create free aldehyde groups, which then react with Schiff's reagent to produce a bright magenta precipitate. Students will learn the protocol steps, optimal fixation (avoiding glutaraldehyde), and interpretation of PAS-positive structures: glycogen, neutral and sialomucins, basement membranes, fungi, and various glycoproteins. The topic highlights critical diagnostic applications, including assessing glomerular basement membrane thickness in renal disease, identifying adenocarcinomas by their mucin content, and detecting glycogen in tumors like seminoma and rhabdomyosarcoma. For Zambian learners in laboratory technology and pathology, proficiency in the PAS technique is essential for routine diagnostic work and examination performance. Mastery enables accurate contribution to multidisciplinary diagnosis in Zambian hospitals, supporting pathology services in oncology, nephrology, and infectious disease.

Cellular Pathology Biomedical Science(Degree)
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Questions
100
Est. time
~100 min
Views
0
Pass mark
50%

How this revision works

Outcomes

If you passWell done! You have mastered the principle, procedure, and diagnostic applications of the PAS stain. This is one of the most important special stains, and your competence will be invaluable in the diagnostic laboratory.
If you don't pass yetThe PAS reaction is a two-step oxidative/conjugation process. Ensure you understand the role of periodic acid (creating aldehydes) and Schiff reagent (reacting with them). Memorize the list of PAS-positive entities and their diagnostic significance. Reviewing stained slide images will help with pattern recognition.

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