The Samurai Pathologist has made an excellent point on GMS technic and
substitution of chromic acid with periodic acid.  Carson's publication in
Journal of Histotechnology, date, volume escape me (hope Freida is looking
in and supplies the info, it is also in archives as this was discussed in
depth not too long ago) on periodic versus chromic acid is also excellent,
and if you miss a fungus (say you ARE looking for Histoplasma) it could be
a problem, possibly legal if you miss it???  

As for addressing the hazardous nature of chromic acid, DAB, AEC other
chromogens are handled with care, and silver solutions must be collected
for disposal, so why the problem with collecting chromic acid.  We are
supposed to wear gloves and protect ourselves from these chemicals. 

Perhaps reading up on GMS (AFIP manual has some good hints, plus Carson's
publication and other text book discussions) is a good idea.  Periodic acid
has its place in fungal staining, but it is used in the Hotchkiss-McManus
PAS technic for fungus and when used with methenamine silver, for basement
membranes. 

Perhaps the vendors are not reading the literature either and any silent
substitution without justification is not acceptable in this lab.  Our lab
would opt for origianl GMS with chromic acid knowing the stronger oxidizer
is better for some fungus.  Even Gridleys stain for fungus uses chromic
acid but with Schiffs reagent.  Checking out the various methods in
histomanuals (Sheehan and Hrapchak Theory and Practice of Histotechnology,
2nd editon) clearly shows the differences in the methods.   


At 09:33 PM 1/15/02 -0500, you wrote:
>Noreen S. Gilman, HT (ASCP) CLS, Supervisor of Histopathology at Broward 
>General Medical Center in Ft. Lauderdale FL asks
>
>>>Once again I find myself asking for special stain help from my fellow 
>histonetters. This concerns the GMS stain. One of my techs tells me that a 
>friend of hers from another hospital is using Periodic Acid instead of 
>Chromic acid, and that there is a written procedure for it. I must admit
that 
>I have been out of the technical area for several years, and I had never 
>heard of this. They are going to fax me a copy, but I thought I'd get some 
>feedback from you guys first.<<
>
>In the last few years many commercial suppliers of GMS reagents have quietly 
>substituted periodic acid for chromic acid. The chromic acid technique is 
>necessary to demonstrate fungal cell walls, particularly in Histoplasma, and 
>periodic acid is not a sufficiently strong oxidant to accomplish this. Most 
>labs I do locum tenens work in don't even realize this change has occurred.
>
>Chromic acid is a strong oxidant and a sufficient environmental hazard that 
>people understandably want to be rid of it. Nonetheless, Good Marketing and 
>Good Management do not replace scientific evidence that periodic acid 
>oxidation is sufficient. If there's any reliable literature on this subject, 
>somebody please cite it!
>
>Bob Richmond
>Samurai Pathologist
>Knoxville TN
>
>
>
Gayle Callis
MT,HT,HTL(ASCP)
Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367
406 994-4303 (FAX)