# New and confused on blood tests



## belafonte (Jun 17, 2014)

I wrote a long question a few weeks ago that was unanswered so I've shortened it in the hopes of getting some help. Thanks in advance!

1) What are the false positives for positive ASCA IgA and IgG (other than celiac)? This is with a negative pANCA and negative ANA as well. Google has not been of much help for me at all.

2) Does anybody know if a gluten free diet could cause anti-TTG (a celiac test I previously had that was positive) to return to negative in a person who has Crohn's and not celiac (I know some people have both diseases, but what about in someone who just has Crohn's)?


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## Malice67 (Jul 2, 2014)

I have Crohn's (and NOT celiac) and in the process of diagnosing they had me do the celiac blood panel. I know that they were VERY specific that I NOT reduce gluten from my diet before the blood test and biopsies or I could get false results (did not ask if they would be false positive or false negative, just made sure to keep eating as normally as I could).  He even did the celiac biopsies during a second endoscopy as the first was in conjunction with a colonoscopy so my diet was altered and my GI felt that would alter the results as well.  Additionally, he felt it as important to have both the blood test results AND the biopsies before he would rule one way or another.

good luck!


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## Patricia56 (Jul 3, 2014)

The gold standard for diagnosing Celiacs is by biopsy. Blood tests are apparently helpful but most docs appear to feel they are not definitive without biopsy confirmation.

I think you need to ask your doctor the technical question about the Prometheus testing. I'm not sure why you are asking the question since generally this testing is to confirm or rule out CD and UC. So I would imagine the false positive is most likely one or the other of those. Only other thing I can think of is eosinophilic disease but I haven't heard of this testing being used to rule out/in that type of problem.

Is your diagnosis uncertain? Have you had scopes w/biopsies?


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