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Thank you to everyone that replied!  Many, many people knew of others
that were not diagnosed until their mid 70s or later.  Several people
also said that since my grandmother is still physically and mentally
fit, any decisions about testing should be her own.  I was also told
(and suspected already) that a "low-gluten" diet probably will not help
if she truly does have celiac disease.  For now she has decided to "live
with 1-2 days/week" of diarrhea.  I guess if it gets worse, that may
prompt her to take more action.

Thanks again!

Kathleen M. Shipley
Beaumont, TX