Screening & Diagnosis of Celiac Disease - Canadian Celiac Association

Screening and Diagnosis of Celiac Disease

Screening

Screening for celiac disease is recommended for any person, child or adult experiencing symptoms associated with the condition (link to page on associated conditions) or if the person is at higher risk of developing celiac disease. celiac screening may be inaccurate among children less than 2 years of age. Routine screening among individuals at higher risk for celiac disease is recommended, including:

First- and second-degree family members (parents, siblings, children, grandparents, aunt, uncle, niece, nephew) of a person with celiac disease

Celiac disease is a genetic disorder, meaning that if you have celiac disease, you carry the HLA DQ2, DQ7 and/or DQ8 gene inherited by one or both of your parents. Therefore, first and second-degree family members of a person with celiac disease have a higher risk of celiac disease

Genetic testing may be performed to rule out celiac disease. It is not used for diagnosis

People with another autoimmune disease, such as type 1 diabetes, Hashimoto’s thyroiditis or Grave’s disease, inflammatory bowel disease (IBD), rheumatoid arthritis, lupus and Sjӧgren’s syndrome.

People with chromosomal disorders such as Down syndrome, William Syndrome or Turner syndrome.

People with immunoglobulin A (IgA) deficiency or IgA nephropathy

Screening for celiac disease is done through a blood test. This test can be ordered by health care professionals such as your family doctor, nurse practitioner or a naturopath. In the medical community, this screening is called serological testing, which uses one or more antibody tests. The main test is called tissue transglutaminase IgA (tTG‑IgA). When screening for celiac disease, a total IgA test must also be done to make sure the body can produce IgA. If a person cannot make IgA, the tTG‑IgA test may not be accurate. People who cannot make IgA have a condition called IgA deficiency, and in these cases, different tests—such as tTG‑IgG—can be used instead. IgA deficiency affects about 2–3% of people with celiac disease.

Other celiac blood tests may be ordered by gastroenterology specialists. These include:

IgA endomysial antibody (EMA)

This test is the most specific for celiac disease, but it is not as sensitive as the tTG-IgA test. About 5-10% of people with celiac disease will not have a positive EMA result. It is usually reserved for specific cases.

Deamidated gliadin peptide (DGP IgA and IgG)

This test can be used to screen for celiac disease in people with IgA deficiency, or in people who test negative for tTG or EMA antibodies

When screening for celiac disease, it is VERY important that the person is eating enough gluten every day. The celiac test is less accurate if a person is avoiding or limiting gluten-containing foods. This is because the immune system may not be making enough antibodies for the test to detect, which can lead to a “false-negative” result. This means that the test did not show celiac disease even though the person may have it. In that case, more testing may be needed to confirm the diagnosis. Early diagnosis through blood testing is important because it helps prevent long-term health problems linked to active celiac disease, such as weak bones and certain types of cancer.

Diagnosis

The diagnosis of celiac disease is confirmed through a procedure called an upper endoscopy with intestinal biopsies.

An upper endoscopy is a relatively safe procedure that usually takes less than thirty minutes. Children are usually put under general anesthesia while adults receive local anesthetics. During the procedure, a gastroenterologist inserts a small tube with a camera through the mouth and down into the small intestine. From the small intestine, the doctor takes several small samples of tissue, called biopsies. These samples are examined under a microscope by a specialist called a pathologist. The pathologist looks for signs of celiac disease, such as villous atrophy (damage and flattening of the tiny finger‑like projections in the intestine) or an increase in certain white blood cells. The lining of the intestine does not have nerve cells, so taking biopsies is not painful, but a sore throat may occur afterward from the tube.

An upper endoscopy with biopsies is considered the best way to diagnose celiac disease because:

The tissue samples can confirm active celiac disease even if symptoms have improved

The proceliac diseaseure can also show if another digestive condition is present

Some children may qualify for a diagnosis based on blood tests and may not need an upper endoscopy. This approach is not recommended by the North American Pediatric Association (NASPGHAN), but it may be used in certain cases.

Note: CD occurs in 2-5% of people with selective IgA deficiency. All symptomatic IgA deficient patients should be referred for endoscopic small intestinal biopsies regardless of their serology results, as false negatives can occur. In asymptomatic individuals with IgA deficiency, the laboratory may be able to perform IgG-TTG or an IgG-deamidated gliadin peptide (IgG-DGP). Negative HLA-DQ2 or DQ8 genetic tests are helpful to exclude the diagnosis of CD because over 99% of patients with CD are positive for HLA-DQ2 or DQ8. However, approximately 30% of the general population tests positive for one of these HLA types and most do not develop CD.