I just researched this recently for procedure writing. I referenced an article
from the CDC that made mention of specific handling guidelines for histology,
and also specifically the formic acid treatment step. I do not have the article
in front of me, but by my recollection I believe that it stated that the formic
acid was a post-fixation step. I found this article relatively easily by using
the search field for CJD from the CDC website. You can check my recollection
here:
http://www.cdc.gov/od/ohs/biosfty/bmbl5/sections/SectionVIIIH-PrionDiseases.pdf
Thanks
Joelle Weaver HTL(ASCP)
> Date: Thu, 22 Jan 2009 13:21:25 -0600> From: sal...@exchange.hsc.mb.ca> To:
> tbr...@holyredeemer.com> Subject: [Histonet] RE: Prion Contamination> CC:
> histonet@lists.utsouthwestern.edu> > Hi,> I was reading your email of Jan.
> 15/09 on the subject of "Prion> Contamination". In it you had made the
> following statement, which I was> curious as to where this information had
> come from. > "the procedure to inactivate using formic acid is followed
> before> fixation and processing. If the tissue is fixed (formalin or other>
> common fixatives) then you would be actually "fixing" the prion's> ability to
> NOT be inactivated". > I had read again the WHO Guidelines on CJD that you
> had a link to &> could find no mention of the fact that the formic acid step
> for> de-activating the prions had to be done before any fixation. The WHO>
> instructions: P. 18 8.2.2 Histopathological examination: states "formic> acid
> treatment consists of placing small pieces of fixed tissue, no more> than 4
> to 5 mm thick, in 50 to 100 ml of 95% formic acid for an hour". I> have been
> dealing with CJD brains for many years always following the> CDC, WHO &
> Health Canada guidelines but have never read any studies that> had indicated
> that the fixing in formalin made the treatment in formic> acid ineffective.
> If you have any further information I would really> appreciate seeing it. >
> Thank you > S. Allen> sal...@hsc.mb.ca> >
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