[Histonet] Responses to IHC CAP Validation question

[McMahon, Loralee A]

Any inspection that I have undergone we have used the 25 to 30 case rule.  Except for the Er/Pr//Her-2.  We use closer to 50 cases.  We also use a TMA to make our lives easier.  The TMA contains known positives and known negatives. 
In cases of t-cell or b-cell markers or cytokeratins.  25 to 30 cases is easy.  But when you are validated for more hard to find markers (SV-40) then fewer cases is acceptable.  We always throw in a slide that we know will not stain for sv-40 like a tonsil - then you can say it has specificity.
Any inspector that I have come across is usually understanding of this.  But I am sure that there are exceptions to this.........especially if they are not familiar with immunohistochemistry. 



Loralee McMahon, HTL (ASCP)
Immunohistochemistry Supervisor
Strong Memorial Hospital
Department of Surgical Pathology
(585) 275-7210
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From: histonet-bounces <@t> lists.utsouthwestern.edu [histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of thisisann <@t> aol.com [thisisann <@t> aol.com]
Sent: Wednesday, April 28, 2010 2:47 PM
To: histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] Responses to IHC CAP Validation question

The following is one respone I rec'd:

1.  I asked CAP who told me that they do not currently have a guideline on
validating but that they
recommend what is in the following book:
Quality Management In Anatomic Pathology, Promoting Patient Safety
Through Systems Improvement and Error
by Raouf E. Nakhleh, MD & Patrick Fitzgibbons, MD editors
sold by CAP !
Chapter 8- Quality Management in IHC
That is what we follow.
I. Get a new antibody and optimize it with your positive control.
II. Once optimized you need to run it on cases expected to be positive
(how many?)
"a suffient size ..."
III. Must also be run on cases expected to be negative. (how many?
IV. In a situation where you cannot expect a lot of cases or such a
case has
never been presented in your lab, then you must say just that.
(ex. some of the hormones we just use a pituitary)







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