Caution: You MUST be eating gluten for celiac disease testing to be accurate! If you want to pursue a celiac disease diagnosis, do NOT go gluten-free until all your testing is completed.
You may have one (or more) different reasons to pursue testing for celiac disease. Perhaps you suffer from celiac disease symptoms, which can range from diarrhea and weight loss to neurological problems and weight gain.
You may have a close family member who was diagnosed with celiac disease, and have learned that guidelines recommend celiac disease testing for relatives, since the condition is genetic in nature.
Regardless of your reasons for wanting to pursue a celiac disease diagnosis, testing for celiac disease is a fairly lengthy process involving blood tests and, ultimately, a procedure known as an endoscopy, used to 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.
Celiac Disease Tests
Celiac disease tests look for your body's reaction to gluten, a protein found in the grains wheat, barley and rye. In people with the condition, eating foods with gluten (which occurs at almost every meal on a standard gluten-containing diet) causes what's called an autoimmune reaction, in which your body's disease-fighting white blood cells mistakenly attack some of your own tissue.
Different autoimmune diseases cause different types of damage in the body. In the case of celiac disease, the white blood cells attack the lining of your small intestine, causing what's known as villous atrophy. Ultimately, this can destroy the lining of your intestine, meaning you're unable to absorb nutrients from your food.
Read more about the basics of celiac disease:
What is Celiac Disease?
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 or not eating enough it's possible for the testing to come up negative, even if you do have celiac disease. Therefore, you should continue eating a normal diet, with gluten-containing foods several times a day, until all testing is completed.
Read more on what foods contain gluten:
Foods That Contain Gluten
If you've already gone gluten-free, 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.
Read more on using the gluten challenge to test for celiac disease:
Undergoing a Gluten Challenge
First Step in Testing: Series of Blood Tests
In most cases, celiac disease blood testing will be the first step toward a diagnosis. There are five blood tests commonly used to detect celiac disease, and they're usually used together, since no one test provides all the answers.
If your body is undergoing an autoimmune reaction to gluten, one or more of these blood tests most likely will come up positive, indicating the need for further testing 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 too little of a particular antibody (a condition called IgA deficiency), and require different blood 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.
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.
Next Step: Endoscopy and Intestinal Biopsy
If your celiac blood tests come back positive or if they're negative but you and your physician agree on the need for further testing anyway the next step is a procedure known as an endoscopy.
In an endoscopy, an instrument with a tiny camera attached is threaded down your throat so that 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 physician 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.
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.
Some medical centers also are using capsule endoscopy, in which you swallow a pill with a tiny camera, to screen for celiac disease. 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.
It's also possible to have positive blood tests but a negative biopsy. This is known as "latent celiac disease." If this is the case, your physician should recommend regular repeat endoscopies, since most people with latent celiac disease ultimately develop full-blown intestinal damage. You also can discuss the possibility of following a gluten-free diet as a trial, to see if any symptoms clear up.
Read more on latent celiac disease:
If I have latent celiac disease, do I need to eat gluten-free?
Dermatitis Herpetiformis Diagnosis Usually Means Celiac
There's 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.
Celiac Disease Genetic Testing Also Plays Role
In some cases, your physician may recommend genetic testing for celiac disease. Genetic tests will look to see if you have one of the two main genes that predispose you to celiac disease.
If you don't have one of these two main genes, the odds of your having celiac disease are very slim, although some cases of celiac have been documented in people who don't carry either gene.
The genetic test for celiac is the one test you can undergo regardless of whether you're currently eating gluten or not the test looks for a genetic predisposition to the condition, not for antibodies that indicate an active case of celiac disease.
If you have a positive genetic test for celiac disease, it doesn't mean you definitely have celiac disease up to 40% of the population carries one of those genes. 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.
Read more on celiac disease gene testing:
Celiac Disease Genetic Tests
I tested positive for the celiac disease genes. Should I stop eating gluten now?
Positive Celiac Disease Diagnosis Means Gluten-Free Diet
Positive testing 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 may seem overwhelming at first (believe me!), you ultimately may find your health improves dramatically and that you don't really mind eating gluten-free.
Negative testing, meanwhile, doesn't mean you definitely don't have a problem with gluten you can test negative on celiac blood tests and biopsy and still suffer from problems related to gluten ingestion.
Some people who test negative for celiac disease nonetheless still have symptoms that clear up on a gluten-free diet. In some cases, people are being diagnosed with gluten sensitivity (sometimes also called gluten intolerance or gluten allergy), a newly recognized and as-yet poorly understood condition. There are no 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.
Read more on gluten sensitivity:
Gluten Sensitivity: Symptoms, Tests, Genetics and Research
Finally, if you test negative for celiac disease, that doesn't mean you definitely 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 catch celiac disease early, you can minimize the damage to your body and potentially ward off complications, such as osteoporosis and malnutrition.
Celiac Disease Center at Columbia University. Diagnosis of Celiac Disease. Accessed Jan. 5, 2012.
National Digestive Diseases Information Clearinghouse. Celiac Disease. Accessed Jan. 5, 2012.
University of Chicago Celiac Disease Center. Antibody Blood Tests. Accessed Jan. 5, 2012.
University of Chicago Celiac Disease Center. Genetic Testing. Accessed Jan. 5, 2012.