AW: [Histonet] IHC pos. & neg. control question

[Gudrun Lang]

I think this approach mixes up antibody-validation and analysis.
The pathologist should be confident, that the used antibody is validated
with several types of tissue and that the special antibody stains positive
epitopes positive and negative epitopes negative.

But the point is, that the patient tissue is unknown and shows perhaps
characteristics, that lead to unspecific staining. And this has to be
compared to the specific staining in the sample.

Gudrun Lang

-----Ursprüngliche Nachricht-----
Von: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] Im Auftrag von
Jean-Martin Lapointe
Gesendet: Donnerstag, 19. Mai 2011 19:26
An: histonet <@t> lists.utsouthwestern.edu
Betreff: [Histonet] IHC pos. & neg. control question

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
 
 



------------------------------

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







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