[Histonet] Floaters

Thu Oct 6 10:19:25 CDT 2011

The recent paper by Platt et all (Tissue Floaters and Contaminants in the Histology Laboratory, Arch Pathol Lab Med, Vol 133, June 2009) details floaters from waterbaths and staining process pretty well. 

Waterbaths do not appear to be a contributor. They literally found only ONE tissue fragment in waterbath water saved from an entire day of sectioning from 13 waterbaths. And it was in the water, not on a slide. They apparently did not identify ANY waterbath-derived floaters on any slide. They attribute this finding to the fact the tissue is still in paraffin so the tissue was either on the slide or stuck to the side of the waterbath, not floating in the water. 

To determine the extent of staining-derived floaters they measured the amount of tissue fragments found in each staining station. The vast majority were in the first xylene and alcohol baths. After the 95% alcohol there were only very rare tissue fragments in the rest of the baths. 

They found the staining process does contribute floaters (besides those that are clearly in the block), but apparently the do not derive from the fragments in bottom of the reagent containers. The floaters were from the other slides in the specific rack stained. The key finding was that BLANK slides put through a stainer at the end of the day (after staining over 1300 slides and accumulating the maximum amount of tissue fragments in the reagent baths) DID NOT PICK UP ANY FLOATERS.

ALL the floaters that they determined had come from the staining process occurred ONLY when tissue slides were included in the stain rack (They alternated blank and tissue slides in the rack). So, the tissue seen in the stain dish does not appear to contribute to floaters. 

A stain instrument vendor repeated this experiment in our lab and came up with the same result.

Our pathologists were mixed on the floater question. Some felt a system that eliminated floaters would be beneficial. Others thought floaters were easily detected and the vast majority could be ignored. It remains to be determined it is cost effective to replace the current system with one that would eliminate floaters. It does not appear to be a sole reason to replace the current system. 

Tim Morken
Supervisor, Histology, IPOX
UCSF Medical Center
San Francisco, CA, USA

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Rene J Buesa
Sent: Thursday, October 06, 2011 6:34 AM
To: histonet <@t> lists.utsouthwestern.edu; Janice Mahoney
Subject: [Histonet] Floaters

This is a very interesting subject indeed. To start I always take "with a grain of salt" whatever a vendor tells me because their opinions may (or may not, but just in case) biased to the products they sell. The same thing goes for any automobiles salesperson of any automobile make claiming the "wonders" of the make they sell compared with other makes.
Now, to the floater. I have also seen pieces of sections on the bottom of staining dishes. They are there because they fell-off the stained section. My question is: what are the possibilities of that piece of lost stained section that fell from its original slide, "re-float" and magically adhere to another slide? I really think that the possibilities range from almost none, to none.
Going to the water bath: yes, this is a major source of floaters because a piece of a section left in the water bath can be picked up in another slide along with a section from another case. That is why it is mandatory to swipe the surface of the water bath with  a tissue after each case is cut. The source can be defined if we keep a record of the sequence in which the blocks are cut (as was standard procedure at my lab).
Whenever we ended with a floater in a section we went immediately to the block to determine if the floater came from the block or the water bath.
The other sources, either during description, cassetting or embedding are going to end in the block and it is very difficult to determine the origin. The only thing to do is to make sure that embedding wells where the forceps rest and heat, are thoroughly cleaned when the embedding ends.
But I think that the main thrust of the question deals with floaters coming from the staining dishes: as I wrote earlier I give to this source a very slim and almost impossible chance.
René J.

--- On Wed, 10/5/11, Janice Mahoney <mamawooo <@t> hotmail.com> wrote:

From: Janice Mahoney <mamawooo <@t> hotmail.com>
Subject: [Histonet] (no subject)
To: histonet <@t> lists.utsouthwestern.edu
Date: Wednesday, October 5, 2011, 8:11 PM

Hello everyone,After being home from the NSH for a few weeks I have been pondering an issue that I think bears discussion on the histonet.There have been several papers published regarding "floaters" and the amount determined to come from traditional staining buckets.  There was also a poster presented at the NSH this year on the subject.When I approached several vendors of H&E stainers about this issue.  The answers were surprisingly pretty much the same.   It is not an issue!  Now I understand how one company can make this claim as their stainer uses fresh stain on each slide.  The explanations from the other companies were insulting and just plain did not make sense to me.  I was told by a Histo tech vendor that "All Histo techs know that floaters come from the water bath."  Well, she was talking to a histo tech and I know for a fact that floaters come from a variety of places.  I have seen them from the doctor's office or procedure room to
 the stainer and every step in between.  Sometimes if the "floater" is in the block it is very difficult to determine where it originated.  We can however eliminate the water bath and stainer as the origin in these cases.  One company told me that the design of the solution bottle eliminated floaters because floaters float and their stainer draws solutions from the bottom of the bottle.  I have probably changed thousands of staining dishes during my 40+ year career (yes, I am old) and I have seen lots of little pieces of tissue at the bottom of the staining dishes.  So, no, not all floaters float.  I would love to hear feedback from others on this.  I guess I would appreciate feedback about the floater issue as well as how a few vendors can make such claims and expect Histology techs to buy it.  I really felt that a few comments were insulting to our profession and to the knowledge and expertise we possess. JanOmaha             
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