How do you diagnose Crohn's vs celiac disease?

July 14, 2009 10:08 PM

How can doctors tell the difference between Crohn's/IBD and celiac disease?

I'm looking for (research-based) information that explains how doctors can diagnose Crohn's vs celiac disease.

For example, say a Crohn's diagnosis was made from barium, flexible sigmoidoscopies, colonoscopies and various symptoms over the years. What markers would show that this is Crohn's and not celiac? Or vice versa? I can find comparisons of Crohn's and ulcerative colitis, but I can't find anything that explains how Crohn's is different from celiac disease.

Thanks.

posted by acoutu to health & fitness (10 comments total)

I was misdiagnosed as having Celiac when I had IBD. The first, less invasive way of diagnosing Celiac is to go on a wheat elimination diet. If you feel better and symptoms go away- then there's your diagnosis. If not, they can do an endoscopy. With an endoscopy the doctor can conclusively diagnose celiac. Villi are damaged by Celiac, so if the doctor sees evidence of damage to the Villi he'll know you have Celiac.
posted by bananafish at 10:31 PM on July 14

But would villi be damaged if you had Crohn's?
posted by acoutu at 10:35 PM on July 14

For one thing, as I understand it, you can have DNA testing to see if you are at risk for Celiac disease. The DNA testing is not used to diagnose celiac disease, but can exclude the diagnosis because you must have certain genetic markers in order to develop Celiac disease.

Having these so-called "celiac disease genes" does not mean you're guaranteed to have celiac disease. In fact, the vast majority of people with the genes never develop celiac disease. Having the genes only means you have a risk of someday developing celiac disease. On the other hand, if you don't have these genes, your odds of developing celiac disease are slim to none. More info. here.
posted by gudrun at 10:57 PM on July 14

There is a blood test for celiac disease that tests for certain antibodies to gluten that will be present in an individual with celiac. These antibodies will not be present if an individual has Crohn's or IBD.

From the NIH:

People with celiac disease have higher than normal levels of certain autoantibodies—proteins that react against the body’s own cells or tissues—in their blood. To diagnose celiac disease, doctors will test blood for high levels of anti-tissue transglutaminase antibodies (tTGA) or anti-endomysium antibodies (EMA). If test results are negative but celiac disease is still suspected, additional blood tests may be needed.
posted by fuzzbean at 11:06 PM on July 14

My understanding is that during the colonoscopy, they take a biopsy and the lab work on this will give a 100% positive for Crohn's disease (BTDT). Coincidentally, at the time when I started having the symptoms, a co-worker of mine was also getting similar ones. He Celiac disease is harder to positively diagnose - his was diagnosed through a fairly uncommon (at the time) blood test that he insisted upon.
posted by plinth at 3:19 AM on July 15

Definitive diagnosis is by biopsy for both diseases, as mentioned above.
posted by objdoc at 5:57 AM on July 15

except that definitive biopsy for Celiac disease is from the first part of the small bowel, while Crohn's is generally biopsied in the large bowel. Crohn's can affect other parts of the bowel, so this isn't universally true, but it's the general approach.
posted by cameradv at 7:52 AM on July 15

Some of what has been said above is untrue. In most cases, the clinical presentation and in particular the extent of bowel involvement along with biopsy and blood test results can help differentiate these two disease.

But there is a small potential for diagnostic uncertainty particularly with Crohn's disease limited to the small bowel when a biopsy fails to identify the hallmark pathological features of Crohn's disease. Suggestive biopsy findings (from the duodenum) alone are not enough for a definitive diagnosis of celiac disease in the absence of antibodies in the blood that are also consistent with celiac. Villous atrophy on pathology specimen may be due to celiac, but it may also be found in Crohn's, bacterial overgrowth, tropical sprue and a number of other conditions. This should prompt careful assessment of other clinical, laboratory or pathological features that might prompt the diagnosis of one of these other conditions. If there's no other clear cut evidence of Crohn's (or other disease) and a suggestive biopsy is all you have, a presumptive diagnosis is entertained and patients will often be treated for celiac at that point. I'd say a response to gluten-free diet in addition to pathological findings is then probably adequate for a diagnosis, even if there were no antibodies present. However really, the combination of celiac specific antibodies and a duodenal biopsy consistent with the disease is more convincing. To add even more confirmation, symptomatic improvement as well as possible improvements in the blood tests while on a gluten-free diet might really confirm things.

In patients that have blood tests that are positive for celiac but a pathology specimen that is negative for the disease, the diagnosis is again murky. For some, this leads to repeated endoscopy for more tissue to evaluate, referral for second opinions, or again, a trial of therapy as previously described.

There is clearly a genetic component to celiac, and there is a DNA test for specific HLA-alleles that are associated with the disease. However at this time genetic testing is not, as far as I'm aware, a part of the "standard" diagnostic approach. Some experts may be using genetic tests with increasing frequency to differentiate murkier cases but I suspect that these tests have only been available for a year or so, and they may suffer from poor specificity. Again, I could be wrong on that as I'm not an academic gastroenterologist.

Again, most of the time Crohn's versus celiac is not a difficult diagnosis to make, but in rare cases it can be a challenge, and really what I've described is the tip of the iceberg, and for all I know, may already be behind the times on the issue. That's why if the diagnosis remains unclear, I'd suggest seeking out care at an academic center with gastroenterologists experienced in the subtleties of such diagnoses.
posted by drpynchon at 10:05 AM on July 15

Thank you all for your responses. Dr Pynchon, if the patient has indeed been diagnosed with Crohn's, would celiac have been ruled out? Or are there definitive hallmarks of Crohn's that would rule out celiac and not cause confusion. Say a patient has had fistula, abscess, fissures, various states of blood in stool and has had biopsies that indicate Crohn's. Based on my own research, I believe these to distinguish Crohn's from celiac. But is there still room for confusion? I can't find any studies that show how they can tell the difference, especially given that many people with Crohn's do have celiac. And if the patient, who was diagnosed with Crohn's by two separate specialists 10+ years ago now has a sibling with celiac and may have child who has celiac, I just wanted to know how the diseases are distinguished.

(I am not seeking a medical opinion. I just wondered how doctors know which is which. There are several sites and journal articles that explain IBS vs celiac, but not IBD vs celiac.)
posted by acoutu at 10:33 AM on July 15

Just to be clear, there are two different blood tests that can identify celiac disease: one is the test for antibodies to gluten (or rather gliadin, which is the protein in the gluten that causes the problem) and the other is a DNA test of the patient that identifies if he/she has an HLA type that is associated with celiac disease. The gliadin antibodies test is now a common enough test that it is usually included in a standardized blood test panel given at many gastroenterologists' offices, so I would hope that if you know someone with IBD that their doctor, if at all competent, should have taken the time to check for the antibodies already. The HLA test is pretty new.

Neither test is considered definitive proof without also doing a biopsy, but sometimes you can skip that if other factors warrant it. Personally, I had tested positive for antibodies and did much better after a few months on a gluten-free diet, so my doctor and I were fine with skipping the biopsy and assuming I have celiac disease. Years later, I happened to find out that my HLA type is indeed one of the ones associated with celiac disease, after being tested and typed for the national bone marrow donor database.
posted by Asparagirl at 9:48 AM on July 16 [1 favorite]