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

Hello Listmates:
This is in reference to the question I asked concerning my niece who
came back with IgG positive and IgA normal (negative?) per her
primary doctor for celiac disease. Right now she is on her cruise eating
whatever!! She will see my GI after her return.

People answered with both children and adults having celiac from these
results. With permission from one of our readers, please let me share
the following information:

Both IgA and IgG gliadin antibodies are detected in sera of patients
with gluten sensitive enteropathy (celiac disease).  IgG anti-gliadin
antibodies seem more sensitive but are less specific markers for disease
compared with IgA class antibodies.  IgA anti-gliadin antibodies are
less sensitive but are more specific.

The IgA antibodies have a specificity of 97% but the sensitivity is only
71%.  That means that, if a patient is IgA positive, there is a 97%
probability that they have CD.  Conversely, if the patient is IgA
negative, there is only a 71% probability that the patient is truly
negative for CD. Therefore, a positive result is a strong indication
that the patient has the disease but a negative result doesn't
necessarily mean that they don't have it.  False positive results are
very uncommon but false negative results can occur.

On the other hand, the IgG anti-gliadin antibodies are 91% specific and
have an 87% sensitivity.  This means that they will show positive
results more readily but there isn't as strong a correlation with CD.
It is less specific.  Patients with other conditions but not afflicted
with CD will occasionally show positive results.   It can occur in
patients with other autoimmune diseases or with no disease association
at all.  This test might yield false positive results but is less likely
to yield false negative results.

A sensitive testing protocol includes testing for both IgA and IgG
anti-gliadin antibodies since a significant portion of celiac patients
(approx. 5%) are IgA deficient.  This combined IgA and IgG anti-gliadin
antibody assay has an overall sensitivity of 95% with a specificity of
90%.

The primary reason to test for the IgG gliadin antibody is to catch
these patients who are IgA deficient.  It is known that the IgA
deficient patients usually have higher levels of IgG antibodies to
gliadin.

As to your question about a diagnosis based upon the IgG gliadin results
alone, - - No!!  The diagnosis cannot be made based only on these
results.  IgG anti-gliadin antibodies are detectable in approximately
21% of patients with other gastrointestinal disorders.

Immunology is fairly accurate but it is far from being an exact science.
All of the lab tests, regardless of the type or source, are presented as
"aids to diagnosis".  They cannot be used alone as a basis for diagnosis
but rather are intended to be considered in conjunction with the
physical examination of the patient as well as the reported symptoms,
etc. by a trained physician.

My note: Since my sister has rheumatoid arthritis and was diagnosed with
colon cancer over 8 years ago (still in remission or considered cured),
Tom suggested she definitely see a GI if not for celiac but for some
other problem.     Thanks Tom --- for your wealth of information.

Cindy in NJ