Celiac Disease Screening & Diagnosis
Screening for Celiac Disease
People with celiac disease who eat gluten have higher than normal levels of certain antibodies in their blood. Antibodies are produced by the immune system in response to substances that the body perceives to be threatening.
These antibodies are:
- Anti-tissue transglutaminase (tTG)
- Anti-endomysium (EMA)
- Anti-deamidated gliadin peptides (DGP)
A positive antibody test suggests that a person might have celiac disease, but it is not conclusive. A biopsy is needed for confirmation.
Antibody tests are only accurate when a patient is on a gluten-containing diet. Those concerned about celiac disease are strongly discouraged from starting a gluten-free diet without having had a firm diagnosis. Any change in the diet, even as briefly as a month or two, can complicate diagnosis.
A screening test is often used when an individual is in a risk group for celiac disease, regardless of symptoms.
1. Every child 3 years and older or adult with a close relative who has biopsy-confirmed celiac disease.
A close relative is a parent, sibling, or child and they should be tested regardless of symptoms.
2. For children with celiac disease symptoms who are younger than 3 years old, antibody testing may not always be accurate.
However, they should be evaluated by a pediatric gastroenterologist, especially if they experience failure to thrive or persistent diarrhea. It can take up to a year for children eating wheat or barley-based cereals to generate an autoimmune response to gluten that will show up on a blood test.
3. Anyone who has a related autoimmune disorder. If they test negative, the test should be repeated on a periodic basis.
These conditions include insulin dependent diabetes mellitus, Hashimoto's thyroiditis, Graves' disease, Addison's disease, and genetic syndromes such as Down, Turner, or Williams.
4. Anyone who has experienced persistent miscarriage or infertility where a medical cause could not be found.
5. There are many other symptoms that could indicate celiac disease. This includes persistent gastrointestinal symptoms, bone density problems, dental enamel hypoplasia and fatigue.
If you are concerned about your symptoms, ask your doctor about testing.
When an individual is diagnosed with celiac disease, their entire family must be tested for the condition, since they are now at risk.
First-degree relatives (such as parents, children and siblings) have a 1 in 22 chance of developing celiac disease in their lifetime. Second-degree relatives (such as aunts, uncles and grandparents) have a risk of 1 in 39.
DNA testing is available (via either blood test or cheek swab) to determine if an at-risk individual carries the genes responsible for the development of celiac disease.
There are two main reasons for using the genetic test when evaluating an individual for celiac disease.
- If celiac disease needs to be ‘ruled out”. This is when an individual does not possess a necessary risk factor for the development of celiac disease or does not have a genetic predisposition.
- If an individual has celiac disease symptoms and has been on a prolonged gluten-free diet, but has not had a biopsy, the gene test is often the only way to determine if symptoms are related to celiac disease.
The gene test does not diagnose celiac disease. It places an individual into an at-risk group for celiac disease, which indicates the individual should be closely monitored with antibody testing in the future.
HLA gene testing measures the presence or absence of genetically programmed molecules found on the surface of some cells. This test for celiac disease can be performed at any time after birth (and even on the cord blood at birth), since an individual is either born with or without these factors and that does not change over time.
Diagnosis of Celiac Disease
If antibody tests and symptoms suggest celiac disease, the physician needs to establish the diagnosis by obtaining tiny pieces of tissue from the upper small intestine to check for damage to the villi. This is done in a procedure called an endoscopic biopsy. This remains the most accurate way to diagnose celiac disease.
This procedure is always performed by a gastroenterologist and is conducted most often in an outpatient surgical suite. The procedure lasts less than half an hour, and sedation and local anesthesia are used.
The procedure involves a long, thin tube with a small camera on the end. The physician will insert the tube into the patient's mouth, down the throat, and into the esophagus. When the tube reaches the patient's stomach, the physician finds the entryway into the small intestine (the duodenum) and inserts the tube there. As the tube is making its way to the small intestine, the camera on the end sends a video image to a monitor. On the monitor the physician can visually assess any evident abnormalities such as ulcers or gastritis.
In the small intestine, the physician examines most of the duodenum, the area affected by celiac disease. The surgical removal of tissue is so important. It is only under a microscope that a definitive diagnosis of celiac disease can be made.
To take some tissue for biopsy, the physician inserts a tiny surgical instrument through the endoscope tube. The physician will take 5 to 6 biopsies. Afterward, some patients experience a sore throat, but most have no memory of the procedure.
DH is diagnosed by a skin biopsy, which involves removing a tiny piece of skin near the rash and testing it for the IgA antibody. DH is treated with a gluten-free diet and medication such as dapsone or sulphapyridine to control the rash.
Drug treatment is short term, usually until the gluten-free diet starts to relieve symptoms. An intestinal biopsy is not necessary to diagnose celiac disease in a patient with DH, since the skin biopsy is definitive.
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