I have been reading the post to this question and it seems to me that there are
different standards depending on the lab that is operating the methodology. I
do agree that the core lab for years have had the instruction and training in
the performance of validation. One thing that comes to mind as well is why has
histology not had this training? Why are we not getting this from our
certification agency, our professional societies and biggest reason where is
our standardization. It seems to me that with all these regualtions in plac
for so long, why were we missed. Is it because when inspected through CAP we
are being inspected by a pathologist rather than a histo tech? These are some
of the questions at hand. I to see new standards within the CAP checklist as
well as other regulatory organizations that will affect the future of the
Anatomic Pathology community. But I think we need is to provide a underlying
architecture for our peers, so that we can begin the transition to the future.
This is only the beginning, there is still Digital Image Analysis and
Telepathology. It funny we are looking to become a hybrid of radiology and the
core lab, but with the best of both worlds. Tim great structure for the
validation study.
-----Original Message-----
From: histonet-boun...@lists.utsouthwestern.edu on behalf of Morken, Tim
Sent: Wed 6/23/2010 9:48 AM
To: histonet@lists.utsouthwestern.edu
Subject: RE: [Histonet] New CAP question ANP.22760
Joe,
You wrote : The folks in the 'clinical' lab have been performing more
comprehensive and complex validation procedures for a very long time ..."
Those were my thoughts exactly. While the person replying may or may not have
specific histology experience she will have clinical lab experience (however,
my guess is that she is exposed to histology regularly at CAP). Clinical labs
have a bit of an easier time, actually, because they validate primarily to
known concentration controls - analytical controls manufactured at a range of
known concentrations for instance. The institution then adds in their normal
controls for validation.
As far as the current question about validating a new lot of reagent the best
practice is to run parallel tests on the same machine. If that is not easily
possible on a particular manufacturer's instrument then the question should be
asked of them: Why not? If this is a requirement the manufacturer should
provide an easy path to meeting the requirement. However, if that is not the
case then the institution simply writes a procedure to get around the
inadequacies of the instrument (Maybe the vendor can help with that). Then
follow the procedure. That should satisfy inspectors.
An "...appropriate panel of tissues..." is whatever the institution deems
appropriate for the given antibody or reagent. This is a perfect place for
tissue arrays. You can make your own or buy them.
IHC must meet CLIA validation guidelines but since IHC is generally qualitative
the requirements must be understood and methods adapted to a qualitative
scenario. Several IHC and Histotechnology books discuss the subject at length
(Taylor, Dabbs, Bancroft for instance).
Below is a brief overview of how to do that. (for more in-depth info this was
covered in an NSH teleconference I gave last year - PowerPoint, audio and
references available from NSH-, and will be covered in a similar workshop at
NSH in Seattle this year).
1)
CAP General Validation
CAP GEN.42020-42163 Test Method Validation Follows CLIA CFR Sec 493.1253 Does
not apply well to IHC (IHC is usually qualitative)
But the general principle applies:
The laboratory must have data on each test's accuracy, precision, analytic
sensitivity, interferences and reportable range.
Unmodified FDA-cleared or approved tests: the lab may use manufacturer
information or published reports but lab must verify outside data.
Non-FDA cleared: Lab MUST verify or establish analytic accuracy, precision,
sensitivity, specificity and reportable range.
2) Validation includes:
Accuracy:
Compare results with New antibody to a previously validated antibody
on the same tissues
Precision:
Test samples with varying antigen expression
Intra-run, Inter-run tests, 10 slides each (reproducibility)
Sensitivity:
True Positive vs False Negative (higher % FN = less sensitive)
Interferences [Specificity]:
True Negative vs False Positive (Higher % FP = less specific)
Delineate what could interfere to give a false positive or false
negative result.
Reportable Range
Establish a scoring system
Provide the definition of a positive result
3)Sensitivity
Analytic Sensitivity:
Lowest amount of substance detectable by the test
Can only be done with controls of known concentration
Diagnostic Sensitivity:
Ability of the test to determine true diagnostic positive verses false
negative (higher % FN = less sensitive)
Requires comparison to a previously validated antibody
IHC Sensitivity:
Extent to which an antibody can be diluted and still achieve target
recognition. NOTE: This is determined by antibody AND detection system!
4) Specificity:
Analytic Specificity
Accuracy on tests of known positive and negative controls
Controls of known concentration
Determine what could "Interfere" to confound the result
Diagnostic Specificity
Ability of a test to determine true diagnostic negative verses false
positives (Higher % FP = less specific)
Requires comparison to a previously validated antibody
IHC Specificity
Ability of an antibody to bind exclusively to its particular antigen
in the absence of staining of other molecules
Or, staining of other structures in addition to target structures/cells
(Sensitivity and Specificity adapted from: Theoretical and Practical Aspects of
Test Performance, in Immunomicroscopy, Taylor & Cote, 2005)
Tim Morken
Supervisor, Histology / IPOX
UCSF Medical Center
San Francisco, CA
-----Original Message-----
From: histonet-boun...@lists.utsouthwestern.edu
[mailto:histonet-boun...@lists.utsouthwestern.edu] On Behalf Of jmye...@aol.com
Sent: Tuesday, June 22, 2010 6:51 PM
To: tjas...@copc.net
Cc: histonet@lists.utsouthwestern.edu
Subject: RE: [Histonet] New CAP question ANP.22760
Tom:
As much as I agree with your acknowledgment that its seems a bit odd for
the CAP to have a blood-banker responding to AP-related issue, I'm actually
not surprised. The folks in the 'clinical' lab have been performing more
comprehensive and complex validation procedures for a very long time, and they
wonder why IHC isn't expected to follow the same requirements as chemistry,
immunology, etc. -- IHC is, after all, an awful lot like ELISA. And
rightfully so, because IHC is, under CLIA (which supersedes CAP), considered
highly-complex, non-waived testing -- and is, therefore, subject to the same
Quality Systems regulations (in particular, 42CFR493.1252-1256, 1273, and 1281)
as
the testing performed in other areas of the lab.
Could it be that, because AP produces qualitative results that are
interpreted by a pathologist and CP produces quantitative results that are
interpreted by an analyzer, we somehow think that CLIA rules don't apply to
IHC? I
certainly don't have the answer to that, but it make me wonder what the
future holds. As witnessed by some of the newest CAP 'standards' (including the
question in question...no pun intended), e.g. ER/PR, where a minimum of 20
positive and 20 negative specimens must be tested, and where 10 of the
positives must be weakly positive -- an acknowledgment that validation specimens
must be carefully selected in order to obtain appropriate results), it
certainly doesn't appear that the regulation of IHC testing is going to become
more relaxed.
Joe Myers, M.S., CT(ASCP)
------------------------------
Message: 12
Date: Fri, 18 Jun 2010 12:38:07 -0700
From: "Thomas Jasper" <tjas...@copc.net>
Subject: RE: [Histonet] New CAP question ANP.22760
To: "Mark Tarango" <marktara...@gmail.com>
Cc: _histo...@lists.utsouthwestern.edu_
(mailto:histonet@lists.utsouthwestern.edu)
Mark,
Did you notice the credentials from this CAP representative? MT with a
Blood Bank specialty I believe. What I glean from that is...more than
likely this person does not grasp the logistics of "contemporaneously"
staining identical Abs from separate lots. She also likely does not
understand the logistical application for detection and automation
either.
I'm not trying to be overly critical of this person. I'm sure she is
quite intelligent and would not have the MT/SBB if she wasn't
intelligent. It comes down to a lack of understanding Anatomic
Pathology testing application re: automated IHC. I believe this is a
common problem in and out of CAP. Many lab directors and other folks in
positions of authority without AP/Histology/Cytology backgrounds seem to
believe that broad clinical lab modalities apply to Anatomic Path
scenarios. I used to refer to this in my former position as - "Trying
to put the yoke of clinical lab onto anatomic path." We are
laboratorians, but in many instances do not fit the general clinical lab
mold.
It's unfortunate that CAP has put this person in the position to
respond. It is apparent to me that she's not grasping the particulars
here. She probably never will unless she decides to go into a working,
automated IHC "tissue" lab and take the time to ask questions and
understand (learn) what we're all about.
Thanks,
Tom Jasper
Thomas Jasper HT (ASCP) BAS
Histology Supervisor
Central Oregon Regional Pathology Services
Bend, OR 97701
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