ASCP Tissue Fixation and Decalcification 3

Question 1

What is the primary purpose of decalcification in histological tissue preparation?

Accepted Answer

To remove calcium mineral deposits so calcified tissue can be sectioned

Answer

Decalcification removes calcium salts from hard tissues such as bone and teeth, making them soft enough to be sectioned on a standard microtome without damaging the blade.

Question 2

Which decalcifying agent is most commonly used for routine bone processing in histology?

Accepted Answer

Hydrochloric acid (HCl)

Answer

Hydrochloric acid (5–10% HCl) is widely used for routine decalcification because it is effective, relatively fast, and provides acceptable tissue preservation compared to other strong acids.

Question 3

What is the primary advantage of using EDTA for decalcification compared to acid methods?

Accepted Answer

It preserves tissue morphology and antigenicity better, enabling IHC and molecular studies

Answer

EDTA chelates calcium ions slowly and gently, preserving cellular morphology, antigenic epitopes for immunohistochemistry, and nucleic acids for molecular pathology testing.

Question 4

Which endpoint test uses a chemical reaction to confirm that decalcification is complete?

Accepted Answer

The ammonium oxalate test, where no white precipitate in the used decal fluid confirms completion

Answer

A few drops of ammonium oxalate solution added to the spent decalcification fluid will form a white precipitate (calcium oxalate) if calcium ions remain; a clear solution indicates complete decalcification.

Question 5

When is formic acid decalcification preferred over hydrochloric acid?

Accepted Answer

When nuclear morphology and DNA preservation for molecular studies are important

Answer

Formic acid (5–10%) is a weaker organic acid that decalcifies more slowly but causes less tissue damage, better preserving nuclear morphology and DNA integrity for molecular pathology.

ASCP - Histotechnician Test Practice Test

ASCP - Histotechnician Test Practice Test

ASCP Tissue Fixation and Decalcification 3