Diagnosing Celiac Disease & Gluten Sensitivity in Adults
NYU Langone gastroenterologists—doctors that specialize in diseases of the digestive system—are experts in diagnosing celiac disease and gluten sensitivity. Celiac disease is an autoimmune disorder in which the immune system mistakenly attacks the digestive tract after a person consumes gluten, a protein found in wheat, rye, barley, and other foods and beverages. Some vitamins, medications, and personal care products such as lip balm contain gluten.
During digestion, food passes through the intestines, where nutrients are absorbed into the body. Most of this absorption occurs in the small intestine, where tiny finger-like projections along the small intestinal lining, called villi, “sweep” the nutrients from food into the bloodstream.
People with celiac disease, however, have a genetic susceptibility to recognize gluten differently. When someone with celiac disease eats food that contains gluten, it triggers the immune system to attack the small intestine. The body forms antibodies, or proteins, that attempt to remove gluten from the body as if it were a foreign invader. The antibodies also attack the lining of the small intestine, causing inflammation.
Over time, recurrent inflammation damages the villi in the small intestine, and the body doesn’t absorb nutrients very well. This can lead to malnutrition and unwanted weight loss. The chronic inflammation also can cause abdominal discomfort.
Gluten sensitivity, also called non-celiac gluten sensitivity or gluten intolerance, may cause uncomfortable digestive symptoms similar to those of celiac disease, but the two conditions are not the same. Gluten sensitivity does not cause intestinal inflammation or damage, nor does it trigger the production of antibodies after a person consumes gluten.
Both of these conditions differ from a wheat allergy, in which the body produces an immune response to a specific component in wheat. A food allergy occurs when the immune system overreacts to a food protein. People with a wheat allergy can usually stop the symptoms by avoiding all foods with wheat. Unlike people with celiac disease, young people with a wheat allergy may eventually outgrow it in adulthood.
Symptoms and Causes of Celiac Disease
People who have celiac disease commonly experience weight loss, as well as digestive symptoms, including diarrhea, abdominal pain, and bloating.
Some people notice mental and emotional symptoms, such as an inability to concentrate, commonly described as “brain fog,” or depression.
Not everyone with celiac disease experiences the same symptoms. Some people have no digestive complaints whatsoever, yet routine blood tests reveal low levels of vital nutrients, such as iron, vitamin B12, or vitamin D. NYU Langone doctors take all of these signs and symptoms into account when making a diagnosis.
The exact cause of celiac disease remains largely unknown. However, more than 99 percent of people with celiac disease test positive for two genetic variations known as HLADQ2 and HLADQ8. Not everyone who carries these variations develops celiac disease; in fact, most people don’t.
Some theories suggest environmental factors trigger celiac disease in people with these genetic variations, but more research is needed. Researchers have found that a family history of the disease increases a person’s risk.
Because celiac disease is a chronic autoimmune disorder, people with the disease may be at risk for other conditions in which the body attacks healthy tissues. Among the most common are rheumatoid arthritis, an autoimmune condition in which there is painful swelling in joints, and autoimmune hepatitis, which causes persistent inflammation of the liver.
Other associated autoimmune conditions include Hashimoto’s thyroiditis, an inflammation of the thyroid gland that often leads to hypothyroidism, or an underactive thyroid; Sjogren’s syndrome, in which the glands that produce tears and saliva are inflamed and damaged; microscopic colitis, in which there is inflammation in the colon; dermatitis herpetiformis, a chronic, blistering skin rash; type 1 diabetes, in which the body has trouble maintaining healthy blood sugar levels; and others.
Infertility and changes in the menstrual cycle have also been observed in women with celiac disease. Osteoporosis, a condition that causes bones to become weak and fragile, may also occur more frequently in people with celiac disease because the lining of the small intestine doesn’t absorb enough calcium and vitamin D to maintain strong bones.
Rarely, long-standing, untreated celiac disease can result in a type of cancer called lymphoma—specifically, enteropathy-associated T-cell lymphoma—that affects the small intestine.
Diagnostic Tests for Celiac Disease
If you experience digestive symptoms or signs of poor vitamin and nutrient absorption, such as unexplained weight loss, an NYU Langone gastroenterologist can perform diagnostic tests to determine whether celiac disease may be the cause. For adults, doctors typically recommend both blood tests and biopsies, in which tissue samples are examined under a microscope, to confirm the diagnosis.
Most people with celiac disease have abnormal levels of certain antibodies—proteins that recognize and destroy foreign invaders, such as viruses and bacteria—in the blood as a result of the body’s immune response to gluten. Your doctor tests your blood to look for unusually high levels of these antibodies.
The blood test is not reliable unless you have been regularly eating gluten. If you have been on a gluten-free diet, the doctor may recommend eating foods containing gluten for two to four weeks before the blood test. As little as 3 grams of gluten per day may be sufficient. This is called a gluten challenge.
Your doctor may also order a blood test to look for the genetic variations associated with celiac disease, HLADQ2 and HLADQ8. While almost everyone with celiac disease has one of these genetic variations, they also occur in many people without the disease—25 to 30 percent of all Caucasians test positive. Therefore, genetic testing is effective only to exclude celiac disease as a diagnosis.
Genetic testing is not affected by whether or not gluten is consumed at the time of testing.
If a gastroenterologist suspects celiac disease, he or she may suggest a procedure called an upper endoscopy to obtain biopsies, or tissue samples, of the small intestine. By analyzing the tissue samples under a microscope, doctors can confirm whether celiac disease is the cause of symptoms. This procedure is routinely done under sedation to ensure comfort.
During the procedure, a gastroenterologist inserts a small, flexible tube with a camera and light on its end, called an endoscope, through the mouth and into the first part of the small intestine, called the duodenum. The physician examines the lining of the duodenum for signs of inflammation, such as damage to the villi, the carpet-like projections that line the small intestine.
The gastroenterologist takes several tissue samples, or biopsies, from the duodenum and sends them to a laboratory. A pathologist, a physician who studies diseases under a microscope, examines the tissue for characteristics of celiac disease, including damage to the villi and the presence of inflammatory cells in the intestine.
If a person’s symptoms, blood tests, and biopsy results are consistent with celiac disease, doctors prescribe a strict, lifelong, gluten-free diet and recommend testing to monitor for celiac disease-related health issues. If any test results are inconclusive, the gastroenterologist may recommend additional tests.
Diagnosing Non-Celiac Gluten Sensitivity
Currently, there is no test for gluten sensitivity. People with digestive symptoms that suggest celiac disease should see a gastroenterologist to determine their risk for either celiac disease or gluten sensitivity.
If celiac disease has been ruled out, your NYU Langone gastroenterologist may recommend avoiding gluten for a few weeks. If the digestive symptoms improve, you then reintroduce gluten into your diet to see if the symptoms return. If the symptoms improve on a gluten-free diet and return when you consume foods that contain it, gluten sensitivity may be responsible for your symptoms. It is important to do this under your gastroenterologist’s supervision to ensure the most accurate diagnosis.
Although non-celiac gluten sensitivity isn’t well understood, recent studies show that gluten sensitivity and irritable bowel syndrome, a disorder that affects the colon, may occur together. Neither gluten sensitivity nor irritable bowel syndrome pose a serious threat to a person’s health, but they can negatively affect wellbeing if left untreated.