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

I originally asked a question about the significance of a positive antigliadin test without a positive tTG or EMA.  I've posted summaries of these responses below, but several things do stand out:  

-Several people who had a positive antigliadin test (IgA and/or IgG) and negative tTG and EMA, but who were also clearly symptomatic, reported a dramatic improvement in their symptoms on a GF diet.  This was essentially regardless of biopsy results.  Several were never biopsied, one had a negative biopsy and one had a positive biopsy.  With examples like these, I don't see how it can be true that you need a positive tTG or EMA in order to have CD.  I will re-iterate advice given to me by Dr. Murray, that in family members with the HLA type for CD, 10% will have a positive biopsy.

-A positive antigliadin at least requires retesting every few years.  People are often told that the antigliadin test doesn't indicate CD, but that they should be retested later.  It would not be safe to assume that a positive antigliadin doesn't mean anything.  One listmate pointed out the work by Dr. Hadjivassiliou indicating neurological damage occurring in the presence of positive antigliadin antibodies without CD.  The exception to this might be in the case of one listmate whose children were negative for the CD HLA-type but still had positive antigliadin.  I don't see how repeated testing of tTG or EMA could be helpful in this case. 

-HLA typing is important and may exclude CD even in the presence of positive antigliadin.  (But now I wonder if an HLA type inconsistent with CD will exclude all the possible negative effects from gluten exposure)  

-other tests that are not routinely given may help to diagnose CD, such as breath tests, or challenging biopsy tissue with gluten. 

I don't know if this summary has clarified anything, but it has caused me to put more credence into the research I've seen about blood tests missing a lot of CD, such as this recent study:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12853995&dopt=Abstract

I received other advice, mainly taking a better-safe-than-sorry approach, which is to go ahead and have a biopsy just to be sure, or to go ahead and put them on a GF diet at least for now.  I would probably be inclined to go completely GF right now, but frankly I need to convince the rest of the family of the need to do either of these.  I was hoping for a more definitive result from blood testing, but maybe it is not possible. 

My conclusion right now is that it would be a good idea to have the HLA typing done, and look into the possibility of a breath test (see abstract below), as well as allergy testing.  Here is an abstract regarding the breath test:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12643292&dopt=Abstract

Someone also sent a link to a good article with an algorithm for the diagnosis of CD, indicating that a biopsy should be done with any positive antigliadin test!
http://aafp.org/afp/20021215/2259.html


Here are synopses of the individual responses:

Listmate's son is mildly symptomatic but has a very high antigliadin IgG.  All other blood tests negative and allergy test for wheat also negative.  Biopsy showed inflammation, which GI doc did not interpret as CD.  Biopsy slides currently being reviewed by a CD specialist.

Listmate had a 3 year old granddaughter that was anemic and otherwise symptomatic.  Only her antigliadin IgG was elevated.  This was dismissed by several doctors, but a biopsy by Dr. Fasano was positive.  This child's brother, also positive for antigliadin IgG and symptomatic, had a biopsy that was "suspicious" but was not put on a GF diet and is doing well now.  In an interesting twist, 2 other family members had all negative bloodwork but positive biopsies.  Another family member had positive antigliadin IgA but a negative biopsy.

one child with CD, the other child showed a weak positive for antigliadin IgG, but normal antigliadin IgA, tTG and EMA.  Their pediatric gastro said not to worry for now but to have him retested in a few years.

a 4-year old daughter with CD, the other child, age 2, had a positive antigliadin IgA, but a negative tTG.  Was retested after adding more gluten to her diet (she had been eating mostly GF due to her sister's CD), and this time the antigliadin IgA was normal, but the tTG was weakly positive!  Advised to continue eating gluten and will be retested in a month.  The doctor wants to see a higher tTG before doing a biopsy.

1 listmate had blood tests that were weakly positive for both antigliadin IgA and IgG on 2 occasions, but negative for tTG.  Her biopsy, read by a CD specialist, was negative.  However, the CD specialist put her on the GF diet anyway, in spite of the negative results, and her symptoms, including seizures, diarrhea and bloating are 100% improved.  Two of her 4 children have high antigliadin IgG levels and negative tTG.  Their pediatrician says that they do not have CD.

1 child had positive antigliadin IgG, but negative antigliadin IgA and tTG.  He had symptoms of small size and a very bloated belly.  After 6 months on a GF diet the bloating was gone.  An endoscopy done at that time (without a gluten challenge) showed a rough appearance to the small intestine.  He has improved on the GF diet.

A listmate had positive antigliadin IgG, but negative antigliadin IgA and EMA.  No tTG was done.  She went on the GF diet but is now considering a gluten challenge.  Every time she has gluten she gets very sick.  She is positive for both genes.  She has been told that there is only a 2% chance of having CD with a negative EMA, but also that EMA tests are subjective and prone to error.

One listmate had no symptoms but was tested because both of her children have CD.  She had positive antigliadin IgA.  She has been told by several doctors that this does not indicate CD.  CD specialists at a conference said that if you are negative on tTG and EMA you do not have CD, but indicated that she should be retested every few years.  She is considering HLA typing.  

Listmate with positive antigliadin IgA and IgG, but negative EMA.  No biopsy.  Health improved dramatically on the diet.  Her GI doc indicated that improvement on the GF diet is the "gold standard" for him.

One listmate with no positive tests, but symptoms improved dramatically on the GF diet.

One listmate, a nursing student, sent this info about antigliadin tests from a reference book:
" Values are for a child greater than 2.
Negative less than 25
weakly positive 25-50
psoitive greater than 50
IgG antigliadin antibodies are detected in sera (blood) of patients with
gluten-sensitive enteropathy.  IgG antigliadin antibodies seem more
sensitive but are less specific than the IgA class antibodies.  ....A
negative IgA result in an untreated patient does not rule out
gluten-sensitive enteropathy, especially when assocaited with elevated
levels of IgG antibodies.  A significant portion of celiac patients are IgA
deficient wihich can serve as an explanation for this occurrence.  In
treated patients known to express IgA antibodies the IgA gliadin antibody
level represnts a better inddicator of dietary compliance than the IgG
level."

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