Validation/Quality Control

Question 1

What is validation?

Answer 1

confirmation, using objective evidence, that specific requirements are consistently fulfilled

Question 2

What is verification?

Answer 2

A study used to determine whether a test system meets specifications

Question 3

Whatis the purpose of an IHC protocol

Answer 3

To determine whether an antigen is expressed in a tissue

Optimization to reduce false positives and false negatives

And to achieve a high intensity stain with minimal backgrund

Question 4

What pre-analytic fators may affect IHCresults?

Answer 4

Cold Ischemic time
Time in fixative (too long or too short)
The type of fixative
Incorrect accessioning delays

Question 5

What analytic factors ay affect IHC results?

Answer 5

Too strong antigen retrieval causing tissue damage

Antibody selection

Picking he correct chromogen (AEC vs DAB)

Does the protocol in the product insert match the digital program on the machine?

Question 6

What is the difference between qualitative and semi-quantitative testing?

Answer 6

Qualitative is only positive or negative: is teh antigen present in the tissue

Semi-Quantitative: interpreted according to an arbitrary scoring system (ex 0 to 3+) which describes staining intensity, distribution, and % positive cells

Question 7

What are the CAP guidelines for controls?

Answer 7

10 positive and 10 negative neoplasm (tumor) samples shuld be run

At least one control should be included per run

Doesn’t specify weak or focally positive samples, however they may be beneficial for certain antibodies

Question 8

Why do we use positive controls?

Answer 8

Positive contols contain the antigen at known, relevant, and stable levels

A known positive ctrl must be included in every IHC run

Also helps veryify correct temperatures and incubation times

Question 9

Why do we use negatiive controls?

Answer 9

Tissue without the specific antigen present, or absent in specific regions. This helps to document the specificity of staining

There should be no staining of structures known to lack the antigen

Question 10

What are internal tissue controls?

Answer 10

Also known as “built-in” controls
Contain the target antigen in normal tissue elements in addition to teh tissue elements under investigation

These can replace positive controls, but are typically used as an additional internal control (ex vein is supposed to stain as well as something else, lets you know if the stain worked)

Question 11

What are tissue process controls?

Answer 11

Proteins generally expressed in all tissues at the same level

They may act as a control for the staining process as well as pre-analytical steps