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Old 09-06-2010, 12:38 PM
jccgf jccgf is offline
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Join Date: Aug 2006
Location: Wisconsin
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jccgf jccgf is offline
Senior Member (jccglutenfree)
 
Join Date: Aug 2006
Location: Wisconsin
Posts: 1,581
15 yr Member
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Hi Amy,

The immunoglobulin A test is looking for a condition called IgA deficiency. Some people don't make any or enough IgA and in those circumstances other IgA antibody testing is not reliable. Your son is not IgA deficient; he tested in normal range for total IgA. All other tests are normal except for the positive t-transglutaminase IgG (aka anti-tTG IgG).

The positive t-transglutaminase IgG is significant and probably indicates celiac disease is present. In general, a positive anti-tTG IgA has a positive predictive predictive rate in the neighborhood of 95-98%. I'm not sure if the anti-tTG IgG rate is quite as high, but it is still considered a positive test for celiac disease.

Good thing he didn't wait any longer to have the blood work done after beginning a gluten free diet because the antibodies can drop off rather quickly. So, he might have had even more positive results had he done the blood work prior to beginning the diet. IgA class antibodies drop off faster than IgG antibodies, so that might explain why he didn't get a positive anti-tTG IgA but still showed a positive anti-tTG IgG.

Quote:
RESULTS: Twenty patients could be followed during GFD and all antibody titres fell sharply within 1 month after introduction of a GFD and continued to decline during the survey interval. Thirty days after beginning the diet only 58, 84, 74 and 53% of all patients had positive antibody levels of tTGrh, tTGgp, EmA and AGA respectively. CONCLUSIONS: As the antibodies used to confirm the diagnosis of CD fall rapidly and continue to decline following the introduction of a GFD, it is important that health care providers carefully inquire about the possibility of self-prescribed diets before patients sought medical attention.
Antibody levels in adult patients with coeliac disease during gluten-free diet: a rapid initial decrease of clinical importance. PMID: 15554953
Hopefully he and his doctor will see the anti-tTG IgG as enough proof of celiac disease to remain gluten free for life.

Often, a GI will want to perform an intestinal biopsy to confirm the diagnosis. Again, there is the problem of beginning the diet prior to the testing. Biopsy results may not be an accurate indicator in someone who has already started the diet.

Quote:
Are you scheduled for a biopsy? Are you eating gluten?
Any changes in your diet can affect the accuracy of your biopsy results. It is necessary for you to be eating gluten every day for at least 4-8 weeks before the procedure. If you are scheduled for a biopsy and are not eating gluten, talk to your doctor about what is necessary to obtain accurate results. If you have a biopsy and have eaten gluten only a short time before the test, you and your physician will not know if a negative test result is accurate or due to your diet.
If your son has already started the diet, and particularly if he has noticed any improvement already... it might make more sense to continue to move forward on the diet rather than be talked into a gluten challenge of consuming gluten again for 8 weeks to be biopsied. It will be interesting to see whether his doctor takes a practical approach or a textbook approach. Also, you can be gluten sensitive without showing biopsy damage needed for a celiac diagnosis, so even if your son ended up with a negative biopsy... given his isolated positive blood test after two months, I would encourage him to remain gluten free. My guess is he would have also shown positive to antigliadin (AGA) IgG which is an indicator of gluten sensitivity had it been run. It has been replaced with the deamidated gliadin antibody, which isn't quite the same.

You can read more about the various antibody tests used in diagnostic testing here:
https://sites.google.com/site/jccglu...gnostictesting

Let us know what the doctor say about the results he got. Did a GI or primary care doctor order the blood work? Was your son very symptomatic? With typical or atypical symptoms?
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Last edited by jccgf; 09-06-2010 at 12:53 PM.
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