Celiac Testing Myth #4 - Doctor Knows Best

It’s tempting to assume that doctors are up on all the latest research. But celiac and gluten-intolerance research is changing fast, and much of what doctors were taught about it is no longer the best information out there. In the past 15 years the estimates of how many people have celiac disease have gone from 1 in 10,000 to at least 1 in 133! So forgive your doctors if they do not think to check for it without some prompting!

Since realizing that doctors can’t possibly know everything and ask all the right questions during every visit, I’ve changed my approach to doctor visits, with great results. If you are considering getting tested for celiac, make sure to ask your doctor about all of these tests:

Labs for Celiac Screening

In order to get valid results, you must be eating a full gluten diet (at least 20 grams a day) for at least 3 months prior to testing. Some anti-inflammatory medications such as steroids (even topical) used in the month prior to testing can also invalidate results.

When your labs come back, get a full copy of them, along with the reference ranges. Reference ranges tell what the normal range of values is for each test. Without this information, you won’t be able to interpret your results, since every lab is a bit different. With a copy of your test results, you will be able to get a second opinion on your doctor’s interpretation of them.

Blood Work
Celiac disease is defined by damage already done to the lining of the small intestine. The “gold standard” diagnosis is biopsy of the small intestine. Because of this, many doctors will not give a diagnosis of celiac disease on blood work alone. However, blood work is usually the first step in screening for celiac disease because biopsies are so invasive. Researchers are now finding that there are many forms of gluten intolerance. They are also finding that people with positive bloodwork who have negative biopsies can go on to develop classic celiac damage. Positive bloodwork is a very strong sign that you have celiac disease.

Here is the list of tests included in a typical full celiac panel:

  • Total IgA (Immunoglobulin Antibody) Some people have low total IgA. If you are deficient in Total IgA, the other tests involving IgA are invalidated.
  • tTG IgA (Anti-tissue Transglutaminase) This is very strongly correlated with celiac disease, however, some people with diseases such as Type 1 Diabetes, Hashimoto’s thyroiditis, HIV, and autoimmune liver conditions can have a falsely positive tTG test. Those conditions all have a higher incidence in celiacs, though, so there is a chance you may have both conditions.
  • EMA IgA (Anti-endomysial Antibody) This test is very specific to celiac disease. If these levels are elevated it’s celiac! However, this test is not as sensitive as tTg IgA
  • AGA IgA (Antigliadin IgA antibodies) Positive results indicate intolerance, and potential for celiac. Is being repaced by DGP IgA
  • AGA IgG (Antigliadin IgG antibodies) Positive results indicate intolerance, and potential for celiac. This may be positive in people with low Total IgA.
  • DGP (anti-Deamidated Gliadin Peptide) IgA This is a newer test. It is more specific to celiac disease than the tTG and AGA tests, and can sometimes catch celiac disease in younger children and people with deficient Total IgA.
  • DGP (anti-Deamidated Gliadin Peptide) IgG This is a newer test, replacing AGA IgG

Update:Cyrex Labs has more comprehensive panels available, that include these tests but test for more ways you could be reacting to gluten, and other foods that could be triggering similar responses. Many of the naturopaths I know are now using them. Check out the list of available tests here.


Normal Villi and Celiac Villi

Normal Villi and Celiac Villi image from CueFlash

The endoscopy is still considered the official gold standard of celiac diagnosis, though many doctors consider positive bloodwork adequate. Reasons to go forward with an endoscopy are to:

  • find out the extent of the damage establish a baseline for follow-up testing
  • confirm a negative diagnosis
  • receive an official diagnosis

If receiving an endoscopy, make sure that the doctor plans to take 6-8 samples from different areas of the small intestine and duodenum and that they will be sent to a qualified lab even if they “look fine.” The samples will be viewed under a microscope and given a Marsh score that tells how severe the damage is. A colonoscopy is not the same as an endoscopy and can not diagnose celiac disease. There are a few other conditions that can cause a positive result. However, false negatives are far more common. Celiac damage isn’t uniform, and in the early stages it can be hard to spot.

People who have a negative biopsy but positive blood work or a family history of celiac are sometimes told to stay on a gluten diet and retest every three years. Other doctors treat positive blood work as a positive diagnosis, and recommend a completely gluten-free diet.

Update 1/26/2012: There are new standards for official diagnosis of celiac disease in children without biopsy coming out.

Skin Biopsy

The blisters of dermatitis herpetiformis are extremely itchy and break easily.

Another way to be diagnosed with celiac disease is to test positive for dermatitis herpetiformis. The rash can be anywhere on the body, but is usually distributed symmetrically. It is commonly found on buttocks, back of neck, scalp, elbows, knees, back, hairline, groin, or face.

Another look at dermatitis hepetiformis. Image courtesy of wikipedia

This rash forms extremely itchy, watery blisters that break easily and then turn red and scabby. The whole area can look red from blisters that are healing. In order to confirm a diagnosis of dermatitis herpetiformis, a biopsy of the clear skin next to a blister is taken and analyzed for IgA. The antibodies are destroyed under the rash itself, so this is very important!

Celiac bloodwork and endoscopy may be negative, but a dermatitis herpetiformis diagnosis still makes you positive for celiac disease. People with dermatitis herpetiformis usually need to drastically reduce their iodine intake in addition to completely cutting out gluten.

DNA Testing

DNA testing can give you an idea of how likely it is that you have celiac disease. But since this post was so long, it got its own post!

So… Doctor Knows Best? Myth: Plausible

Check out the other myths we’ve exposed so far:

This post is a part of Food Renegade’s Fight Back Friday!

Related posts:

19 comments to Celiac Testing Myth #4 – Doctor Knows Best

  • Marcus

    I read about the gluten-rectal-biopsy as being the most sensitive and specific test there is.
    It only takes a 6 hour gluten rectal challenge followed by a rectal biopsy.

    My doctor never heard of this test.

    I would be ready to do as I would find out in one day if I have celiac, instead of eating bread for 3 months and feeling sick.

  • LoL

    This author is an idiot. The most well versed Celiac institutions and doctors say false positives are more frequent then false negatives in blood tests. It is sad how anyone with half a brain can post B.S info on the internet. The author of this article needs to be put on medication as she is clearly demented and far off from reality. Please don’t post medical articles when you are an uneducated baboon.

    • I was going to flag this as spam but it does look like you took the time to try and make a relavent point so I’m giving you the benefit of the doubt. Since these comments were directed to me, I’m letting the personal attacks go. Such posts towards others will be deleted.

      On the incidence of false positives vs false negatives, I urge you to read the following excerpt and related supporting studies, which can be found here:

      Seronegative celiac disease

      Both the anti-tTG and the EMA titers correlate with the severity of villous atrophy [26-29]. As a result in the presence of partial villous atrophy either antibody may be negative. In addition the mode of presentation of the celiac disease, i.e. presence of silent or subclinical celiac disease may be associated with a negative EMA [30]. Clinically seronegative celiac disease is similar to sero-positive celiac disease [23, 28] In view of the possibility of the presence of celiac disease in the absence of a positive anti-tTG or endomysial antibody the presence of a positive IgA AGA should prompt a biopsy [13]. Several studies have demonstrated that reliance on either anti-tTG or endomysial antibody as a single test will underestimate the prevalence of celiac disease [23, 25, 31, 32].

      Causes of false positive celiac serologic tests

      The endomysial antibody test is virtually 100% specific for celiac disease. However anti-tTG has been reported to be positive in the presence of liver disease, especially cirrhosis [33], diabetes [34, 35] and severe heart failure [36], as well as arthritis [37] and various autoimmune disorders [38]. The use of human tTG as the antigen in the test kit adds some greater specificity. Antigliadin antibodies may be present in inflammatory bowel disease [39], collagen vascular disease [40], and in many healthy people as well [41].

      You are correct that I am not a doctor. I am not giving medical advice. I am sharing the issues as I have experienced them and researched them, for others to take into consideration while working with their health care practitioners.

  • Okay, so I had a Celiac panel done in 2009. A that time, these were my levels for the values they tested:
    Gliadin AB: IgA=22
    (20-30=weak +ve)
    Gliadin AB: IgG= -ve
    Tissue Trans IgA = -ve
    They said since my TtG IgA is negative, it’s “not consistent with active Celiac.” The positive result is apparently: “specific indicators of gluten sensitive enteropathy, however can occur in patients with unrelated intestinal disorders & in patients with hypergammaglobulinemia”
    So, is the Gliadin AB IgA level totally pointless, as my gastroenterologist said? I just had a colonoscopy (he wouldn’t do an endoscopy) and was told I have IBS, and he’s not doing any other work up. He also insists people with celiac never suffer from constipation, only diarrhea.
    I’m so confused. I’ve requested a repeat of the bloodwork…

    • First question… were you eating a gluten-containing diet in the months leading up to your tests?

      If I were in your shoes, I would try to get a second opinion, and rather than repeating the blood work, if you really want to make sure you’ve ruled out celiac completely, I would insist on an endoscopy (so long as you are still eating gluten) with a minimum of 6 samples taken, preferably by a different doctor.

      It is possible that you do not have celiac disease, which is a specific type of autoimmune attack on specific tissues of the small intestine. Even if an endoscopy comes back negative for celiac disease, you may wish to cut gluten out entirely and see if it helps your symptoms.

      • Hi Mama,
        Yes, I was eating gluten before the test.
        I probably should get a 2nd opinion, you’re right. I think I’ll repeat the blood, though, as well, because I gather they’ve updated the tests and also I can check to make sure I’m not deficient in TtG, resulting in a false -ve. I’m certain it’s at least a gluten intolerance, if not Celiac, based on many symptoms.
        I wouldn’t care as much if it weren’t for my 7-yr old who has stomach problems, too. Since cutting out all dairy, we’re both a bit better, but he’s been on laxatives for over 3 years now (courtesy of his paediatric gastroenterologist). I’d rather come up with answers than just treat symptoms without getting to the bottom of it. He had the same week +ve AB IgA that I did…
        Thanks for listening!

  • P.S. Yes, I know Mama isn’t a doctor but it’s nice to get opinions from people experiencing similar food issues!

  • Marcus

    Hi Mama,
    I’ve come back to have another read and I noticed something in your article…
    I don’t mean to embarrass you, but you might want to reread the article you linked under DGP-IgA.
    It’s DGP-IgG that is better in children with IgA deficiency.

    I don’t agree with the personal attack by LOL above.
    It is quite harsh and too vague as to what he’s disagreeing with.

  • […] if you are having this test done, it may make sense to also have biopsies collected in order to screen for celiac disease at the same time, even if your blood work for celiac was […]

  • […] authors reminded people to get screened for celiac disease prior to going wheat-free, and that they repeatedly emphasized the importance of a strictly […]

  • Corncob

    I have a question, and would value your input. I was having IBS and bad reflux with problems swallowing. My blood tests were negative for Celiac. However, I had stopped eating gluten for three-four weeks before the test because I was sick and had difficulty swallowing. My MD suggested I go gluten free. Was GF for five months. I felt great, BUT was surprised that just eating something made in a facility that processed wheat made me sick. So I went to a gastroenterologist and questioned if he was sure that I didn’t have celiacs. Did a gluten challenge and had an endoscopy that showed increased leukocytes in my duodenum. Only three tissue samples were taken from my duodenum in addition to stomach. The pathologist suggested that it could reflect “gluten-sensitive enteropathy”—celiac disease, but the gastroenterologist’s office only came back saying “maybe your gluten sensitive.” Since I’m two months into the gluten challenge, I thought why not go another month and repeat the IgA test, get a DNA test, and get a second opinion. What would you do?

    • I’m sorry you’ve been so ill! Celiac or not, it sounds like being gluten-free helps, so that’s good news. I don’t know what I’d do regarding further testing in your situation. If the pathologist told me “celiac” and the office said “maybe you’re sensitive,” I might push a bit on it by taking my results to another GI doc and my MD for second opinions. But honestly, that result combined with the feeling better off gluten would be enough evidence for me to go off gluten permanently.

      I think my choice of further testing would depend on *why* I wanted the testing. Here are some questions for you to think about:

      1. What symptoms are you currently experiencing from your gluten challenge? Are you progressively worsening? Are you willing to risk further damage for the sake of a diagnosis?
      2. Why do you feel you need a certain diagnosis of celiac? Does it have implications on your health care coverage or work accommodations or anything like that?
      3. What if you continued the challenge and got a negative or inconclusive result for celiac?
      4. How would that impact your decisions about your future behavior and health?

      Good luck to you, whatever course you take! I hope you get all the answers you are looking for.

  • Julia

    I have been GF (or so I think) for about a year now. I am not sure if I have been missing hidden gluten. I was at an Allergist for another issue on Monday and was tested for celiac. Both of us thought it would come back negative because I haven’t been eating it for a year but to both our surprise, both tests were positive. Any opinion on why I would test positive without having eaten much gluten in the past year? I feel much better on a GF diet and since I tested positive, is that a high indicator for having celiac? I know that I have to have the biopsy to completely know but what if that comes back negative? Does it negate everything else?

    Test Results:

    GLIADIN (DEAMIDATED) IGA ANTIBODY <15 negative- 19.5

    • Hi Julia,
      There are several reasons your test could be positive despite your having cut out gluten. I’ll try my best to explain. Of course you should discuss all this with your doctor(s) rather than just taking my word for it. It sounds like you have a competent allergist 🙂

      First, you say that you haven’t been eating “much” gluten in the past year. If you never really got away from it the damage was continuing. “Just a little” counts where autoimmune reactions are concerned.

      Even if you really stopped eating it and haven’t for a long time, if others in your household are eating it you are likely being cross-contaminated. If you are eating in restaurants and choosing gluten-free menu options, or eating baked goods that people make for you, those can be problems as well.

      With your test results I would definitely be on the lookout for sources of contamination! (Have you read my 100% gluten free post?)

      The blood work really does suggest that you are getting contaminated somewhere, because ttg IgA and gliadin IgA antibodies do not persist long term without exposure. Of curiosity, what did your IgG numbers look like?

      The results of your biopsy are considered the “gold standard” for diagnosis. However, the mechanism for positive results is different from the mechanism involved in a positive blood test.

      While the blood test is looking at the antibodies that form in response to the trigger of gluten, the biopsy is looking at the damage those antibodies have created in the wall of your small intestine.

      So the results of your biopsy will depend on
      1. the extent of the damage done in the first place while you were eating gluten
      2. the extent of your continued exposure to gluten
      3. your capacity for healing, and the speed with which you heal
      4. whether the biopsy samples are taken from the most damaged locations of your gut (celiac damage is spotty rather than consistent)

      It is possible that you have been very good about eliminating gluten in general and that one year was sufficient for significant healing. If your blood results were elevated due to a recent exposure that was not a regular thing, it is conceivable that you would get a negative biopsy despite being celiac.

      Personally, I would consider the blood tests as conclusive. I would still get the biopsy, especially since you have believed yourself to be gluten-free. This will give you a MARSH number, which indicates how severe the damage is. If your dr does a scope at the same time (which they generally do), s/he will also have the chance of spotting other potential issues.

      At that point, you can take further measures to become more gluten-free, and also to work on healing your gut. (Cutting out gluten stops the celiac damage, but healing the existing damage can require more changes.)

      In time, you can get a follow up biopsy. If your MARSH score is the same or worse, more changes will be necessary. If it improves, you are on the right track.

    • Hi Julia,

      I read this and had to comment also. The same thing just happened to me last week! I’ve been on a gluten-free diet for three years now, and my allergist tested my blood for celiac disease last week even though I told him it would come back negative since I was eating gluten-free (and had been for a long time). I was shocked when the deamidated gliadin test came back positive. My TTG was normal but very high normal (18.3, cutoff is <20). Based on the hours of reading and research I've performed since then, the deamidated gliadin test is a very good test for celiac disease and only has a false positive rate around 5%. Given that I am a walking textbook example of celiac disease (all the classic symptoms with no obvious cause except gluten), I'm taking the positive blood test as a personal diagnosis of celiac disease and I probably will not get the biopsy right now.

      Although I felt much better for a while after starting my gluten-free diet three years ago, for the past several months I've been sick again (GI distress, severe fatigue, canker sores). All this time I was thinking I perhaps had a soy issue or some other food issue in addition to gluten since I was eating gluten-free. Now it turns out that all the symptoms were probably just from cross-contamination of gluten, given that I had enough antibodies in my blood to score a positive celiac blood test. And now I'm scared to do a gluten challenge for the biopsy due to how sick I've been lately, if in fact it was all due to trace amounts of gluten (and I now believe it was).

      I think if, down the road, there are interventions or medications for celiac disease that require biopsy diagnosis (there are some in the pipeline), then perhaps then I would attempt the challenge. But for now I'm working harder (i.e. losing my mind) to try and eliminate all sources of gluten cross-contamination so I can stop feeling so sick and miserable every day (it's soooo hard!).

  • Julia

    Thank you so much. I honestly didn’t expect to possibly have celiac because my symptoms are so atypical- I just thought I had gluten sensativity so I didn’t worry about cross contaminiation/eating at restaurants because I felt much better. Those were the only two tests performed- I didn’t have an IgG test. My consult with the GI isn’t for two months so I hope to live like I have celiac until then and then possibly reintroduce if he/she recommends biopsy which I hope they do. Thanks again! So helpful!

  • P4peace

    We had a food intolerance test do e for my daughter and she scored a number 3 ( meaning to not eat wheat rye barley oats gluten spelt cows milk cheese kefir, yoghurt also from cow for minimum 9 mths. (Amongst other 38 foods) Could it be she has celiac ? Or on the way? Or would you just count this as a non celiac gluten sensitivity? ( I would say she has borderline ADD) Would you push for celiac test? I know the biopsy will only show if 100% vili worn down and not show if she is on the way for example 70 %. Is that correct? What is the official celiac test name?
    Sorry for all the questions…dr’s not up to date here it seems.
    Worried mama x

    • I’m sorry I didn’t see this until now! Yes, I would want to get a celiac test done while she is still eating gluten! I would do the blood screening and follow up with the biopsy if positive, to get a MARSH score. The MARSH score does show degrees of damage, but there does need to be substantial damage done before it will be spotted. As for all the many intolerances that were indicated, it is more likely that her gut is “leaky” than she has true allergies to all those foods. Heal the gut and the intolerances will get better! I hope your little one is feeling better and you have gotten more answers since posting this!

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