<<Disclaimer: Verify this information before applying it to your situation.>>

I read your questions with interest.  The questions you ask address what
is really unknown in celiac disease research.  The gliadin IgG is the
least specific of all of the blood tests and least predictive of celiac
disease if all of the others are negative.  But some celiacs will have
just that profile, especially if they have IgA def.  That can be tested
for by measuring the total IgA in the blood, A simple test that it may
be possible to do on the residual serum already taken.  If there is IgA
def. then a biopsy should be done.

If there is no IGA def, another approach is to obtain a skin biopsy for
DH, this is less of a deal that an intestinal biopsy and if the correct
staining and biopsy preparation is done then it can reliably identify
intestinal gluten sensitivity if the patient has dermatitis
herpetiformis.

Seeking a precise diagnosis may be very important when dealing with
these issues in the future.

? difference between gluten sensitivity and celiac disease.  Celiac
disease is defined by a combination of damage to the gut and a
subsequent improvement with a gluten free diet.   Gluten sensitivity (
separate from celiac disease)  is not well defined and many people mean
different things by it.  This definition can vary from a typical
allergy, hives, wheezing to defining it as a "mild form " of celiac
disease. Celiac disease is a definite condition with a definite
treatment.   The other entities if they exist it is not clear what
should be done about those.

Not medical advice

Joe Murray