Re: [Histonet] TB in Lung Specimens
I haven't read the article, so read this with that fact in mind.
When I trained in the 1960s TB was fairly common still. We were taught
to handle TB infected tissues relatively safely. However, looking back
on it we were quite lax compared to today's attitudes towards safety in
There were some things we did that were more likely to protect us than
are done today, though. One of the most important is the duration of
fixation with formalin mixtures. We used to fix a minimum of overnight,
sometimes up to a couple of weeks, mostly because there was no fixation
(pun intended) on a 24 hour diagnosis. Even then it was known that TB
organisms resisted formalin fixation, so known cases were routinely left
for a few days before grossing. Often they would be refixed after that.
The usual approach was to expose the organisms to a minimum of 48
hours in formalin, with a week being better. After that they were
presumed to be safe.
It should be kept in mind, though, that in the past we used longer
processing schedules with quite a bit longer in ethanol and xylene. It
was presumed (no proof) that the fat solvent nature of those affected
any remaining viability of TB organisms by dissolving out the mycolic
acid coat. At any rate, with older long fixation and slow processing we
considered the organisms to be dead.
Today, short fixation and fast processing is the norm so I would suggest
that should no longer be considered true, and that you are indeed at
risk. On the plus side, modern processors do use heat during
processing, and cassettes limit the thickness of the tissue, so they are
less likely to come out unprocessed than they were in the past.
Since TB is on the rise again I think the whole subject should be
reappraised and standard safe working protocols publicised and enforced.
I stress the "enforced" since we all know that protocols are
established and may then be completely ignored because they are
inconvenient. This comes through very clearly with some of the comments
about the (US) CAP inspections on Histonet. We have similar inspections
in BC, Canada with similar attitudes, I might add, and I presume other
countries are the same.
Before I retired I had a long term disagreement with our safety
committee and lab administration regarding this issue. The lab wanted a
24 hour turnaround time, while the safety committee wanted all lab
departments to work with universal precautions, that is, treat all
specimens as if they are infected with the worst possible organism. I
repeatedly pointed out that these were mutually exclusive for TB, HIV,
hepatitis and other things. For universal precautions we would have had
to fix all biopsies for 2-3 days before processing just in case a
formalin resistant organism was involved. That would preclude a 24 hour
diagnosis. I was never able to get an answer to my objections on this
issue, and I consider it to be an area of administrative hypocrisy. I
did, however, make sure my comments were clearly recorded just in case
of a WCB claim by one of the technologists.
The reality is that we are expected to section and stain tissues that
are infected and which may well contain viable organisms. In practice,
the issue then becomes how to do this and work safely. I suggest that
the following should form the basis.
1. Get vaccinated for everything you can. This should be at employer's
expense. If they refuse to pay, get it done, pay yourself and then kick
up one hell of a fuss.
2. Wash your hands frequently. Use soap and hot water and maybe a
brush. Be thorough, not cursory. This helps with squame contamination
on sections, too. Don't forget the face, especially around the mouth
and nose. We frequently touch those areas without being aware of it.
3. Wear gloves. Don't presume this means you need not wash your hands.
4. Wear masks.
5. NEVER cut frozen sections on unfixed TB, HIV or hepatitis cases, ever.
6. Fix tissues as long as possible as a routine.
7. Use as long a processing schedule as you can get away with.
8. NEVER process known TB, HIV or hepatitis tissues with less than 48
9. Sacrilege. Put your own health before that of the patients. You
won't do anybody any good lying in a hospital bed. Do NOT fall into the
trap of making an exception because "the patient needs a diagnosis".
Usually that means someone else can't be bothered to wait.
10. Make a nuisance of yourself with any committees or groups that have
influence in these areas, and don't stop.
This is not exhaustive by any means, and like Patsy, I would like to see
this issue discussed far more thoroughly.
Patsy Ruegg wrote:
> This is alarming. I have not been on histonet for a while, was there
> responses to this? I have been working with formalin fixed paraffin
> embedded tb infected tissue for years without using these kind of
> precautions. Am I at risk for TB infection?
> Patsy Ruegg
> -----Original Message-----
> From: Patsy Ruegg [mailto:email@example.com]
> Sent: Saturday, August 28, 2004 9:51 AM
> To: firstname.lastname@example.org
> Subject: FW: [Histonet] TB in Lung Specimens
> -----Original Message-----
> From: email@example.com
> [mailto:firstname.lastname@example.org]On Behalf Of Andrew
> Sent: Monday, August 09, 2004 2:19 PM
> To: Histonet
> Subject: [Histonet] TB in Lung Specimens
> Hi Histonetters,
> A recent article in Human Pathology suggests that Mycobacteria in formalin
> fixed tissue can remain viable and therefore there is a risk of contracting
> TB from these specimens. It suggests that formalin fixed tissue from
> suspected TB cases should be handled with gloves, gown and mask.
> I wonder if we should be using these precautions for every lung specimen at
> every step in the histological process! If the organisms are still viable,
> trimmings from blocks should probably be bagged and disposed of in
> infectious waste. It could quite possibly end up being the same as with CJD
> brain specimens. What do you all think about this?
> Reference: Gerston, K.F. Blumberg, L. Tshabalala, V.A. Murray, J. Viability
> of Mycobacteria in Formalin Fixed Lungs. Human Pathology, Vol 35, No 5. May
> 2004. pp 571-575
> Andrew Kennedy
> Senior Science Officer
> Anatomical Pathology
> Concord Repatriation General Hospital
> Hospital Road
> Concord NSW 2139
> ph: +612 9767 6115
> Fax +612 9767 8427
> "corpora non agunt nisi fixata"
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