Gudrun:
  Unfortunately there is not much standardization in histology, except for, as you point out, some FDA approved tests, like Her2Neu where almost all labs do it in the same way, specially because manufacturers like DAKO that even provide free steamers and water baths, to assure that the tests (done with their products) are run in a standardized manner.
   
  Appart from this exception any histology lab is run pretty much as it has been run since its start or since the present supervisor "started to take care of (and modify!) things".
  Overnight protocols vary in overall and/or in stations duration; antibody dilutions for IHC vary from lab to lab for the same antibody and also some preffer one detection system over another; automatic staining also "suffers" from the same interlab differences; the reagents and stains are different, and some are "home made" and others bought ; the fixatives also vary and fixation is different.
  You name the step, and you will find that each lab "holds its ground" to "deffend" its procedures and protocols without any scientific basis, except for "preference" or "I have done it like this always". This is unfortunate,  but is a fact of life in histology.
  The thing is that since histology is still mainly a qualitative activity, it does not matter that much (except for some extreme affecting antigens integrity). We process tissue and prepare slides that are going to be used in a qualitative manner, that are going to be used to identify a structural pattern, not to quantify things.
  This is why histology is such a special area of the medical lab and will continue that way until molecular pathology does not take hold of the entire operation, until it will be necessary to preserve DNA and RNA and formalin will be substituted, probably after very "strong fights" dealing with its "universality" and "usefulness".
  Under separate cover I am sending you an article that has been accepted for publication in the Feb./07 issue of Annal of Diagnostic Pathology that deals with these facts.
  I hope I have not added more confusion to the issue!
  René J.

Gudrun Lang  wrote:
  I've read the interesting discussion about microwave processors and have a
general question. Nowadays there is the demand of standardization in
histolabs. From tissue to tissue and from lab to lab we have to minimize the
differences in processing the specimen. So tests like immunohistochemistry
can be performed in high standards and reliance. 

How do labs match this issue when introducing a new technology like
microwave processors? Do they use old and new processors parallel? Can you
run all sorts of tissue with it? If this isn't possible, are there two
"kinds" of paraffin-blocks to make fitting protocols? 

What about these FDA-proved tests? After all the work you have the lab-own
standards, but aren't "allowed" to do the official test?

I think about biopsies, that are partly proceeded in microwaver, partly in
the old instrument over night, specimen fixed in formalin for few hours up
to a week, or fixed in a new reagens without formalin,....



Perhaps someone could share her/his experience with us.



Gudrun Lang





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