Pete, Can't argue with that. I think for the sake of expediency most clinical services run a "known" positive and a patient slide for negative. In the case of H. Pylori, for instance, we may cut a box of control slides and it's possible to go through the area where the organisms were. This also happens with controls that demonstrate positivity by other means epithelium, tumor, etc. We may have to re-run tests in these situations. I believe we are similar to many clinical labs in our reliance on known positives. tj
-----Original Message----- From: pete.peder...@healthonecares.com [mailto:pete.peder...@healthonecares.com] Sent: Thursday, May 19, 2011 2:54 PM To: Thomas Jasper; histonet@lists.utsouthwestern.edu Subject: RE: [Histonet] IHC pos. & neg. control question Thomas, Agreed, however, how can you say with certainty that the control is still good, or the antibody is still performing optimally? Hypothetically speaking, if you had a known positive control and ran it like a patient specimen (positive and negative) and had staining in the negatively stained control that you had been only running as a positively stained control prior, how would you proceed? What good is a positive control without if it is not treated identically as patient tissue. If you had none specific staining in a patient negative but is was also there in your known positive control which you stained negatively as well, then you could mark up to nonspecific staining to reagent or IHC user error. If the negatively stained positive control stains truly negative and the patient negative has nonspecific staining then you would know patient tissue is compromised or has been mistreated somewhere along the way because your positively stained and negatively stained positive controls demonstrate the staining was done correctly, correct? Pete Pedersen B.S. HTL (ASCP) Anatomic Pathology Supervisor -----Original Message----- From: Thomas Jasper [mailto:tjas...@copc.net] Sent: Thursday, May 19, 2011 1:39 PM To: Pedersen Pete; histonet@lists.utsouthwestern.edu Subject: RE: [Histonet] IHC pos. & neg. control question Pete, When you run a positive control. The tissue is already a known positive (or it should be) for whichever antibody you are running regardless of prior handling. It would be impossible for this not to be so. However, with a negative, the concern is seeing how the patient tissue turns out when subjected to all the same conditions, minus the antibody. tj -----Original Message----- From: histonet-boun...@lists.utsouthwestern.edu [mailto:histonet-boun...@lists.utsouthwestern.edu] On Behalf Of pete.peder...@healthonecares.com Sent: Thursday, May 19, 2011 12:31 PM To: gdaw...@dynacaremilwaukee.com; histonet@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-boun...@lists.utsouthwestern.edu [mailto:histonet-boun...@lists.utsouthwestern.edu] On Behalf Of Dawson, Glen Sent: Thursday, May 19, 2011 12:32 PM To: histonet@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-boun...@lists.utsouthwestern.edu [mailto:histonet-boun...@lists.utsouthwestern.edu] On Behalf Of Curt Tague Sent: Thursday, May 19, 2011 11:04 AM To: histonet@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." 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