RE: CJD question, frozen sections

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From:"R.Wadley" <>
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	Dear Hazel,

	As far as I understand CJD remains virtually unaffected by fixation &
processing, so why is there a difference between a frozen & a paraffin.
One of the classic experiments into scrapie (Ovine CJD) is to take a
sample, fix it, process it, block it out, section, stain & coverslip it,
then scrape it off the slide (after clearing back to water) & use the
macerated section to infect a healthy sheep.

	Pathology laboratories whether diagnostic or research, deal with both
hazardous samples & hazardous reagents.  There are procedures to protect
scientists & technicians working in those laboratories.  Diagnostic
laboratories have an obligation to treat all patient samples equally.  To
actively disciminate against individuals who may have or are suspected to
have a particular infectious agent is unethical.  Research can have the
luxury of determining what sort of sample they will deal with, within
limits.  My lab is a semi commercial unit located in a university providing
research resources, I will not run human samples unless they have been
screened for HIV & the various hepatitis viruses.  However, when my flow
cytometer is modified to remove the possibility of infection to the
operator by aerosols, then, under appropriate conditions, there may be
scope to run & more importantly sort infected samples.

	By not performing certain techniques on known infectious or contaminated
samples simply makes lab staff over confident.  My first experience of lab
practicum was in a haematology lab in the late 80's.  A known, tagged HIV
sample came in.  The whole lab was cleared, the staff member assigned to
deal with the sample was gowned, masked, wore eye protection, & was double
gloved.  There was a person on the door to prevent entry to the lab.  Yet
this was a lab that dealt with hundreds of samples per day, statisticly
they probably had at least one HIV positive sample per week.  But because
they were unknown no special precautions were taken.  In this case being
paranoid probably put more people at risk than instituting good laboratory
practice.  "Normal" safety procedures in that lab was gowns & single
gloves, although occassionally the gloves were optional.

	I am not advocating that laboratory staff should put themselves at risk.
I'm saying every sample is potentially infectious and/or hazardous & no
samples should be discriminated aainst just because you happen to suspect
they are infected.  Try a simple experiment, randomly sample the frozens
you do, check back to the patient files, I think you would be very
surprised at the number of infectious cases you routinely cut without all
this trauma you associate with known infectious cases.


	Rob W.

At 16:07 03/15/2000 -0600, you wrote:
>If the CDC states frozen sections should not be performed on known CJD
>specimens I think that in itself is a valid argument.    Afterall, 24 hours
>is not long to wait for 'permanent' sections to be obtained.
>And I doubt waiting 24 hours  changes the protocol for treatment outlook for
>these patients.

R. Wadley, B.App.Sc. M.L.S, Grad.Dip.Sc.MM
Laboratory Manager
Cellular Analysis Facility
School of Microbiology & Immunology
UNSW, New South Wales, Australia, 2052
Ph (BH) 	+61 (2) 9385 3517
Ph (AH)	+61 (2) 9555 1239
Fax 	+61 (2) 9385 1591

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