The advent of antibody testing to diagnose celiac disease has led to a substantial increase in the number of cases detected among children, a new study suggests.

Celiac disease is a digestive disorder caused by an abnormal immune response to gluten, a protein found in wheat, rye and barley -- as well as in many everyday items like medicines and vitamins. The disease damages structures in the lining of the small intestine called villi, which then impairs the body's absorption of nutrients.

Traditionally, classic celiac disease was diagnosed when babies and young children developed symptoms like chronic diarrhea and significant weight loss. But in more recent years, experts have found that celiac disease has a wider variety of symptoms -- including chronic abdominal pain, acid reflux, vomiting and constipation -- particularly in older children.

This greater understanding of celiac symptoms has in large part been credited to blood tests that detect certain antibodies produced in people with the disorder.

These tests have allowed more and more people who have atypical celiac symptoms to be referred for definitive testing with an intestinal biopsy -- where a small piece of tissue is removed from the small intestine to check for damage to the villi.

In the new study, published in the journal Pediatrics, researchers found that the rate of celiac disease diagnoses at their children's hospital tripled after the introduction, in 1997, of antibody testing.

And most of those children, the study found, did not have classic celiac symptoms.

Although the study covered only a single center, the increase in celiac diagnoses is not an isolated situation, according to senior author Dr. J. Decker Butzner, of the University of Calgary and Alberta Children's Hospital in Canada.

Other research has similarly found increases in celiac diagnoses after the introduction of antibody testing.

The current findings are based on 266 children who were referred to Alberta Children's Hospital between 1990 and 2006 for an intestinal biopsy and ultimately diagnosed with celiac disease.

Between 1990 and 1996 -- before antibody tests were available -- 36 children were diagnosed with celiac, 67 percent of whom had been referred for testing because of classic symptoms. The children were typically about 2 years old when diagnosed.

In contrast, between 2000 and 2006, 199 children were diagnosed with celiac, with the typical age at diagnosis increasing to age 9. Only 19 percent of these children had classic celiac symptoms.

Instead, 38 percent had atypical digestive symptoms, like chronic abdominal pain, while 15 percent had non-digestive symptoms, such as iron deficiency and poor growth.

The rest of the children -- 28 percent -- had shown no clear symptoms, but were referred for testing because they had a family history of celiac disease or had medical conditions associated with a higher risk of the disorder, including type 1 diabetes and Down syndrome.

In an interview, Butzner said that blood testing for celiac disease should be performed when a child has chronic gastrointestinal symptoms of any kind that do not improve on their own or respond to treatment.

Testing might also be appropriate for children with a family history or celiac-associated medical conditions -- though, Butzner said, it is controversial whether this should be done in the absence of celiac symptoms.

He also stressed that the antibody blood tests are only a screening procedure and do not provide a definitive diagnosis. A positive test result, Butzner said, needs to be followed up by an intestinal biopsy.

This is important, Butzner explained, because the treatment for celiac disease is to go on a lifelong gluten-free diet. While effective at easing symptoms and healing and preventing intestinal damage, the diet can also be expensive and challenging to follow.

SOURCE: Pediatrics, December 2009.

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