Cheryl Powell, BS, HTL located Freida Carson's article in the Journal of 
Histotechnology in which she probably answers the question we've been asking 
about substituting periodic acid for chromic acid in the Gomori methenamine 
silver stain.

Dr. Carson lengthened the time in periodic acid and increased the 
temperature, and demonstrated that this change in the procedure both 
decreased non-specific staining, and increased the likelihood that 
Histoplasma capsulatum would be demonstrated.

"Our experience indicated that 1% periodic acid oxidation for 5 to 30 min at 
room temperature is insufficient for consistent detection of Histoplasma 
capsulatum, although adequate staining of Aspergillus sp. is obtained. 
Consequently, false-negative results may be reported. We recommend that the 
period of oxidation with periodic acid should be extended to 1 hr at 56 to 
60°C to ensure consistent demonstration of H. capsulatum. These observations 
also underscore the importance of the use of matched positive controls when 
analyzing fungal stains."

The authors did exactly what I suggested in an earlier posting: after an 
index case brought the problem to their attention, they recovered seven 
earlier cases from their files, and showed that the periodic acid technique 
as commonly done failed to demonstrate the organisms in 3 out of the 8 cases. 
I'm particularly impressed by their index case, in which the patient had 
overwhelming active histoplasmosis in the bone marrow, with no staining with 
periodic acid GMS at room temperature.

Could someone on this list with adequate archival material duplicate this 
study and report it to us? - I would suggest calling this modified periodic 
acid technique "Carson's GMS" unless Dr. Carson insists we blame it on her 
junior authors! Are the reprints still available?

Reference:
Inconsistent Detection of Histoplasma capsulatum with Periodic Acid Oxidation 
in the Grocott Methenamine-Silver Nitrate (GMS) Fungus Stain

Freida L. Carson, Jerry Fredenburgh, and John E. Maxwell
1. Department of Pathology, Baylor University Medical Center 
2. Richard-Allan Scientific Kalamazoo MI 
3. Glenwood Regional Medical Center, West Monroe LA

J Histotechnol [June] 1999;22:119

Address reprint requests to: 
Jerry Fredenburgh, Richard-Allan Scientific, 225 Parsons Street, Kalamazoo MI 
45007-3538.

Bob Richmond
Samurai Pathologist
Knoxville TN