[Histonet] IHC pos. & neg. control question

[Jean-Martin Lapointe]

Hi Curt,
I agree with your pathologist. The section that you use as a negative control (without primary) in an IHC run should ideally be tissue that is a known positive, and of the same nature as the test sample. Therefore the best sample is often a section of your positive control tissue. 
The purpose of this negative control is to make sure that any positive staining observed in the test sample is not due to a spurious cross-reaction, unrelated to the primary. I don't think the issue per se is that you are using tissue from the same patient; rather, it is that you are using a sample for which the staining characteristics are not known. For instance, if are using a lymph node section as a negative, for a stain that targets an epithelial marker (eg Her2) in the test breast sample, then your negative tissue is not appropriate, because since lymph node contains no epithelial tissue, it will not stain no matter what. Therefore if your test sample shows a positive reaction in the epithelial tissue, but for some reason that reaction is a spurious false-positive, then the lymph node negative will not reveal that. 
I realize that this is all very theoretical and hypothetical, but I understand the pathologist wanting to be confident in the knowledge that all potential technical issues are eliminated before making his diagnosis.

Jean-Martin

__________________________________
Jean-Martin Lapointe, DMV, MS, dACVP
Vice-President, Pathologie
AccelLAB Inc
1635 Lionel-Bertrand, Boisbriand
Québec, Canada  J7H 1N8
tel:  450-435-9482 ext.247
fax: 450-435-4795
jm.lapointe <@t> accellab.com
 
 



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Message: 24
Date: Thu, 19 May 2011 09:04:24 -0700
From: "Curt Tague" <c.tague <@t> pathologyarts.com>
Subject: [Histonet] IHC pos. & neg. control question
To: <histonet <@t> lists.utsouthwestern.edu>
Message-ID: <019801cc163e$6c1487d0$443d9770$@tague <@t> pathologyarts.com>
Content-Type: text/plain;	charset="us-ascii"

I got this email from a pathologist today. we have always run a positive
with the patient tissue and a negative, the same patient tissue, and had no
problems. Am I missing something. Is there any documented regulation
dictating what needs to be used for the controls. In some cases if we get
one slide of patient tissue, then we will use the pos. and neg. cont. from
the same block but typically it's the pt. tissue that is used for the neg.
control. Thanks for your guidance. 

 

Email: 

"I received slides on sentinel lymph node biopsies with a positive control
on the same slide as the breast tissue, but the negative control was just
the patient's lymph node and did not have the corresponding section used for
the positive control.  The patient's own tissue cannot be used as a negative
control.  The tissue that stained positively must serve as the negative
control without the antibody.  This is critical and you need to correct that
immediately."

 

 

Curt