[Histonet] IHC pos. & neg. control question

[Dawson, Glen]

Pete,

OK, time for an example:

A pathologist orders 4 IHC's on a block.

I run 5 slides total:  4 IHC slides with a section of patient tissue and a known positive.  1 slide with patient tissue only for the negative control.

The one negative control is put through the retrieval/protocol that is most likely to cause nonspecific staining.  I don't run the known positive control tissue used on the 4 actual IHC slides as negative controls.

Perhaps I didn't point out that my original post was addressing the negative control?  I'm a bit surprised by the confusion.

As for the question of "how I know the staining seen in a positive control is truly positive?":  All known positive controls are tested previously so I know that they work for the antibody that I'm using them for and I would assume the pathologist uses morphology and localization of staining to determine that the positive control is working.  That's what I do.

I've gone through 7 CAP inspections utilizing the practices above with no problems thus far.  Perhaps you could enlighten me on IHC requirements that I haven't come across.

Glen D.



-----Original Message-----
From: Pete.Pedersen <@t> HealthONEcares.com [mailto:Pete.Pedersen <@t> HealthONEcares.com]
Sent: Thursday, May 19, 2011 2:31 PM
To: Dawson, Glen; histonet <@t> lists.utsouthwestern.edu
Subject: RE: [Histonet] IHC pos. & neg. control question

Glen,

If I am to understand you correctly you are saying control tissue is not treated the same as patient tissue, therefore is useless as a negative control correct? Then inversely doesn't that mean the same thing towards the use of a positive control? How can you guarantee the positive control tissue was treated the same as the positive stained patient tissue? According to your logic it cannot. Therefore, without the use of a negative control how can you say the staining seen in the positive control is truly positive and not artifact? Best practice says use positive and negative patient and control tissue. Please enlighten me if you know anything to the contrary?

Pete Pedersen   B.S. HTL (ASCP)
Anatomic Pathology Supervisor

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Dawson, Glen
Sent: Thursday, May 19, 2011 12:32 PM
To: histonet <@t> lists.utsouthwestern.edu
Subject: RE: [Histonet] IHC pos. & neg. control question

IMHO: Running any piece of tissue as a control that does not belong to the patient being tested makes zero sense.  Because it would not be from the patient tissue being tested, how do you know if it was handled the same as the patient tissue?  For example:

1) Were they processed the same way?
2) Did the patient tissue dry out in the OR before it was delievered?
3) Was the patient tissue ever irradiated?
4) Does the patient tissue contain any of a number of substances that could cause non-specific staining.
5) Was the patient abducted by aliens?

My point is that running a piece of tissue as a negative control that is not even from the patient being tested throws all of the conditions that the patient tissue was exposed to prior to and during processing out the window.  This makes NO sense.

Glen Dawson  BS, HT(ASCP) & QIHC
IHC Manager
Milwaukee, WI



-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Curt
Tague
Sent: Thursday, May 19, 2011 11:04 AM
To: histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] IHC pos. & neg. control question

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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