[Histonet] IHC pos. & neg. control question

[Tony Henwood]

It still comes down to why test the positive control for false positive reactions after it has already been determined that they are not present.

But what you say about positive controls matching patient's tissue with regards to pre-fixing, fixing and processing is correct but in the real world we cannot guarantee that this would happen. We can only work on averages and hope that conditions are as similar as possible.

In a perfect world we would not need negative, nor dare I say positive, controls.

Regards 
Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC), FFSc(RCPA) 
Laboratory Manager & Senior Scientist 
Tel: 612 9845 3306 
Fax: 612 9845 3318 
the children's hospital at westmead
Cnr Hawkesbury Road and Hainsworth Street, Westmead
Locked Bag 4001, Westmead NSW 2145, AUSTRALIA 


-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Pete.Pedersen <@t> HealthONEcares.com
Sent: Friday, 20 May 2011 5:31 AM
To: GDawson <@t> dynacaremilwaukee.com; 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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