[Histonet] Counter stain for PAS for fungus (Steve McClain)

[Steve McClain]

Change all your reagents.
Change periodic acid every week at least.
PAS unlike many other stains is a chemical reaction and is sensitive to oxidizer 

Personally I see little advantage in fast green, and a common downside is 
overstaining in many labs, hiding fungus and basement membrane.
Faint Hematoxylin is acceptable counterstain.

For certain applications, e.g., dual staining for carbohydrate and mucin, by adding AlcianBlue for 40 seconds is wickedly good.
Dis/Advantage being dual staining methods impose two charges.
Too bad.
Instead of separate stains for mucin and carbohydrate, 
do them both every day and get good at it.
We rarely do a straight PAS any more, either PAS+AB+H or PAS+AB
Subtract the second charge where needed.

The two analytes (carbohydrate and mucin) are different, yet the interpretation is synergistic.
Where you see mucin glommed around a hypha-like structure it is.
AB also demonstrates conidia and microconidia and internal structure in many fungi.

AlcianBlue also stains bacteria, making it useful where polymicrobial (fungal and bacterial) infections are common.
Consider it your biofilm assay.

Many fungi produce mucin making PAS-AB with hema a superb method for detection.
PAS-AB sine hema is considerably more sensitive, especially with pigmented fungal species, 
but interpretation of PAS-AB without Hema is more difficult for pathologists.

Steedman wrote the original description , in 1951 and it remains the best paper.

Steve
Steve A. McClain, MD
McClain Labs, LLC 45 Manor Road, Smithtown, NY 11787 631 361 4000