How Celiac Disease Is Diagnosed

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The diagnosis of celiac disease is a fairly lengthy process. In most cases, you'll first have blood tests done, and then ultimately, will have a procedure known as an endoscopy, in which doctors look directly at your small intestine. In the best-case scenario, you'll have your answer within a few days or a week, but the diagnostic process can take much longer in some areas, especially where gastroenterologists (specialists in the digestive system) are in short supply. Here's what to expect from every stage of the process.

Self Checks/At-Home Testing

Some people go onto a gluten-free diet to see if it clears up their symptoms that might be associated with celiac disease. Whether or not this improves your symptoms, it should be followed up with diagnostic testing by your doctor.

There are at-home screening tests you can purchase for celiac disease. These use a finger-prick blood sample that you send to a laboratory, receiving the results in about a week. A home blood test should always be followed up with medical testing by a physician.

Important: You must be eating gluten for celiac disease testing to be accurate. If you are being tested for celiac disease, do not go gluten-free until all your testing is completed.

Medical guidelines recommend celiac disease testing for relatives of those diagnosed with celiac disease, since the condition runs in families. The familial risk is due to specific genes. Some people take advantage of consumer genetic testing, such as through 23andMe, to screen for celiac-related genes. This testing doesn't require being on a gluten-containing diet. It also only shows a risk of the disease, rather than markers of having celiac disease.

Labs and Tests

In most cases, celiac disease blood testing (which can be ordered by your primary care doctor) will be the first step toward a diagnosis. There are several blood tests commonly used to detect celiac disease, although many doctors will only request one or two of the tests. These tests look for various antibodies. If your body is undergoing an autoimmune reaction to gluten, one or more of these blood tests should come up positive. This indicates that further testing is needed to see if you truly have celiac disease.

However, it is possible for you to have negative blood test results and to still have celiac disease. Some people have a condition known as IgA deficiency that can cause false negative results on some celiac disease blood tests. If you have this (there's yet another blood test that will look for it), you'll need different tests to screen for celiac disease.

In a few other cases, the blood test results simply don't reflect the amount of intestinal damage present. This also is known as a "false negative" test result.

Therefore, if your blood tests are negative, but your symptoms and family medical history still indicate a strong possibility of celiac disease, you should talk to your physician about further testing.

Because the tests for celiac disease are looking specifically for signs of this small intestine damage, you must be eating gluten for the tests to be accurate. If you're not eating gluten-containing foods—or not eating enough of them—it's possible for the testing to come up negative, even if you actually do have celiac disease. Therefore, you should continue eating a normal diet, with gluten-containing foods several times a day, until all your testing is completed.

Of course, some people do go gluten-free before they decide to be tested for celiac disease. If you've already started following the gluten-free diet, you may want to consider what's called a "gluten challenge," in which you eat a set amount of gluten for some period of time, and then undergo testing for celiac disease. This tactic does carry some risks, though, and may not produce the results you want, so talk to your doctor about the potential risks and benefits.

Genetic Testing

In some cases, your doctor may recommend genetic testing for celiac disease. Celiac disease is linked to two specific genes, which are passed down through families. Genetic tests can be done using a swab of your mouth or by drawing blood. The genetic test for celiac is the one test you can undergo regardless of whether you're currently eating gluten or not.

Genetic tests can't tell you if you actually have celiac disease—for that, you'll need to undergo the blood tests and endoscopy described above. But genetic tests can tell you whether you have one of the genes you generally need to develop celiac disease.

If you don't have one of these two main genes, the odds of you having celiac disease are very slim, although some cases of celiac have been documented in people who don't carry either gene.

A positive genetic test for celiac disease doesn't mean you definitely have celiac disease—up to 40 percent of the population carries one of those genes, and the vast majority never develop celiac. However, it does mean you possibly can develop the condition. You'll need to discuss with your doctor your next steps if your celiac disease gene test comes back positive, especially if you have a family history of celiac disease.

Dermatitis Herpetiformis Testing

There is one way you can obtain a diagnosis of celiac disease without undergoing an endoscopy and intestinal biopsy. If you have an itchy, painful blistering skin rash called dermatitis herpetiformis, plus positive celiac blood tests, you're officially diagnosed with celiac disease as well—no further testing required. That's because studies have shown that nearly everyone with dermatitis herpetiformis—which, like celiac disease, is caused by an autoimmune reaction to gluten—also has intestinal damage from gluten ingestion.

However, to obtain a gold-standard diagnosis of dermatitis herpetiformis, you'll need to undergo a skin biopsy. This biopsy looks for deposits of anti-gluten antibodies under your skin.

Imaging

If your celiac disease blood tests come back positive—or if they're negative, but you and your physician agree on the need for further testing anyway—your next step is a procedure known as an endoscopy. This usually is performed by a gastroenterologist, one of the many types of doctors who treat celiac disease.

In an endoscopy, an instrument with a tiny camera attached is threaded down your throat so your physician can look directly at the lining of your small intestine to see if villous atrophy is present. In some cases (but not all), the damage from celiac disease can be seen immediately during this procedure.

However, to confirm the diagnosis, the surgeon also will use the instrument to take tiny samples of your intestine. Because damage from celiac disease can be patchy, the surgeon should take at least four to six samples. These samples then will be examined under a microscope by a pathologist (a doctor who diagnoses disease by examining body tissue directly) to determine if your intestines are damaged. If the pathologist sees damage, you'll be diagnosed with celiac disease.

Some medical centers also are using capsule endoscopy, in which you swallow a pill with a tiny camera to screen for celiac disease. This has the benefit of seeing parts of your small intestine that can't be reached by conventional endoscopy instruments. However, capsule endoscopy doesn't allow the surgeon to take samples of your intestine, and may not be as accurate in identifying damage as traditional endoscopy.

Just as it's possible to have negative blood tests but a biopsy that shows you have celiac disease, It's also possible to have positive blood tests but a negative biopsy. This is known as "latent celiac disease" or sometimes as "potential celiac disease." If you fall into this category, your doctor likely will recommend regular repeat endoscopies, since many people with latent celiac disease ultimately develop full-blown intestinal damage. You also can discuss the possibility of following the gluten-free diet as a trial, to see if any symptoms clear up.

Differential Diagnoses

The combination of positive blood tests and an endoscopy finding of villous atrophy will help rule out other causes of villous atrophy, which include tropical sprue, severe intestinal bacterial overgrowth, eosinophilic enteritis, infectious enteritis, and lymphoma.

Some people who test negative for celiac disease nonetheless still have symptoms that clear up on a gluten-free diet. They may be diagnosed with non-celiac gluten sensitivity (sometimes also called gluten intolerance or gluten allergy), a recently recognized and as-yet poorly-understood condition. There are no generally accepted tests to determine if you have gluten sensitivity—the only way to know is to give up gluten and see if your symptoms clear up.

If you test negative for celiac disease, that doesn't mean you won't develop it in the future. Studies of close relatives of celiac disease patients (who themselves have a high risk of developing the condition) show that repeated screening over the course of years may be necessary to catch all cases.

Therefore, if you have risk factors for celiac disease—"celiac" genes, close family members with the condition, other autoimmune diseases, or even just bad symptoms—you may want to consider setting up a regular testing schedule with your physician. If you are diagnosed with celiac disease early, you can minimize the damage to your body and potentially ward off complications, such as osteoporosis and malnutrition.

The final piece to the puzzle is your reaction to the gluten-free diet—if your symptoms begin to improve once you go gluten-free, you've just confirmed your diagnosis.

A Word From Verywell

Positive test results for celiac disease on your endoscopy and biopsy means you definitely have the condition and must follow the gluten-free diet for life. Although this can seem overwhelming at first, you ultimately may find your health improves dramatically and that you don't really mind eating gluten-free. Truthfully, there are many, many foods you can eat when you're gluten-free.

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