[Histonet] MWO validation.

From:Rene J Buesa

Hi Patsy:
  I completely agree with you. A few days ago I advised an MD do to hold using MWO for breast that was going to be used with IHC tests.
  My argument was as follows:
  1- FDA has approved Her2Neu for FFPE tissues, and they say NOTHING about MWO although it could be assumed that it was using conventional processig
  2-DAKO developed their protocol (later approved by FDA) using conventional tissue processors
  3- IF something happens and a lawsuit is brought, any savy lawyer (and they are savy enough) could "dig-out" the type of processing used and IF it was MWO it is likely that their argument could be accepted by a jury.
  I don't think that a lab individual validaiton could hold in court (against an FDA approved procedure). NEW guidelines by the FDA would be needed (as you point out).
  MWO users beware!
  René J.

Patsy Ruegg  wrote:
Has mw processing been validated for IHC (especially for her2neu) by running
25-100 cases side by side (one piece conventionally processed and the other
mw processed from each of the 25-100 cases) then running the IHC? Until
this is done and reported the new guidelines for her2 testing will require
that any deviation from conventional processing and fixation for 6-48hr
using the FDA approved her2neu kits, labs using mw processing will not be in

-----Original Message-----
From: histonet-bounces@lists.utsouthwestern.edu
[mailto:histonet-bounces@lists.utsouthwestern.edu] On Behalf Of Rene J Buesa
Sent: Tuesday, July 17, 2007 10:17 AM
To: Weaver, Colin; histonet@lists.utsouthwestern.edu
Subject: Re: [Histonet] Microwave v conventional processing

Using the adequate protocols MW processing renders equivalent results to
"conventional" tissue processing, that is the general concensus.
The thing is that unless you use an automated MW tissue processor, a
histotech will have to attend to the process and change reagents manually. 
This can lead to 2 problems: higher exposure of the HT to (usually hot)
chemicals and some degree of inconsistency in the protocol because the time
in each reagent could vary slightly different between runs.
Consider that a few minutes in a conventional protocol is a much lower
percentage of the time in the reagent, than the same amount of time in a
much faster protocol completed with a MW tissue processor.
MW processing should be an option when TAT is an issue and even then there
are numerous manual steps independent of the time the tissue is involved in
the processing step; they are independent of the processing technology and
usually count for the greater part of the total TAT.
Under separate cover I am sending you an article of mine wher I analyze
this issue.
René J. 

"Weaver, Colin" wrote:
Hi - we are trying to go down the microwave route in processing but
inevitably some of our veterinary pathologists are questioning whether
microwave sections are as "good" as conventional processing. Can anyone
point me in the right direction to find any comparison done between
microwave processing and conventional overnight processing with regard
to section and staining quality.

Colin Weaver
Veterinary Laboratories Agency (VLA)

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