Norwegian screening finds three-quarters of those with celiac disease undiagnosed

September 28, 2022

Subsequent gluten-free diet leads to improved health

By Amy Ratner, director of scientific affairs

A wide-spread screening study estimates that nearly 1.5 percent of the residents of one Norwegian county have celiac disease, and before the screening, 75 percent didn’t realize it.

Meanwhile, when those diagnosed with celiac disease through screening went on a gluten-free diet, a majority reported less abdominal discomfort and more energy, according to the study.

The high rate of undiagnosed celiac disease was “rather surprising” given the well-organized Norwegian healthcare system, noted authors of the study, which was published recently in the journal Scientific Reports.

Despite availability of blood tests for celiac disease, the proportion of people with undiagnosed celiac disease remains high, the study says. The authors noted that their study illustrates that a majority of cases of celiac disease were detected through screening of a large group of people unaware they had the condition.

“Such a high prevalence appears to be the rule,” wrote researchers from the University of Tromsø and colleagues.

A 2018 study that reviewed global evidence estimates that the prevalence of celiac disease based on serologic test results is 1.4 percent and based on biopsy results is 0.7 percent. The prevalence of celiac disease varies with sex, age, and location, the study noted. Estimates of undiagnosed celiac disease range from 50 to 80 percent.

Norwegian study results

One third of the entire adult population of Tromsø County, Norway, was included in the screening, a large sample size that was a major strength of the study, according to the authors.

The study was based on surveys that monitor the health of residents of the county, a mixed urban, rural community. More than 75,000 adult residents have participated in one or more surveys since the first was launched nearly 50 years ago.

Researchers based this study on a health survey done in 2007-2008. About 50 people who participated in that survey had previously been diagnosed with celiac disease, making up less than one half of one percent.

Researchers tested for celiac disease antibodies in blood samples from about 12,000 additional survey participants and found about 275 people with positive results. About 175 returned for a follow-up biopsy, and 84 were diagnosed with celiac disease. Biopsy evaluations included immunohistochemical examination as an additional tool for diagnosis. This technique involves performing special tests on biopsy tissue sample to help diagnose disease more precisely.

Estimating prevalence

Of the 103 participants who did not return for a biopsy, researchers estimated 50 had undiagnosed celiac disease based on the rate of positive results in those who did have biopsies and the nearly identical levels of antibodies found in both groups.

These methods of estimating celiac disease can lead to more accurate counting of prevalence, according to Edwin Liu, MD, director of the Colorado Center for Celiac Disease at Children’s Hospital Colorado, who was not involved in the study. “Without counting these individuals who are not biopsied would severely underestimate celiac disease,” said Liu, who has participated in the Diabetes and Autoimmunity Study of the Young (DAISY), the Environmental Determinants of Diabetes in the Young (TEDDY), and Autoimmunity for Kids (ASK), screen children for celiac disease, type 1 diabetes and other autoimmune conditions.

The Norwegian study calculated that .37 percent of survey participants were previously diagnosed, while 1.1 percent were undiagnosed, leading to prevalence of 1.47 percent.

Benefits of a gluten-free diet

Researchers went on to investigate whether those who had a biopsy and were newly diagnosed would improve after following a gluten-free diet for more than one year. Of those who adopted the diet, about three quarters reported reduced abdominal discomfort and nearly two thirds had more energy.

“A gluten-free diet resulted in significant improvements in overall gastrointestinal symptoms, diarrhea and health-related quality of life,” the study says.

Still, the difficulty in diagnosing celiac disease outside of widespread screening might be attributed to non-gastrointestinal symptoms in those who have celiac disease, who before being diagnosed report fewer abdominal complaints than those who don’t have celiac disease, as was found in the study. Meanwhile, the celiac disease patients were found to have significant intestinal damage when biopsied, the authors note.

“Many patients with celiac disease are not conscious of their symptoms prior to their diagnosis and may become fully aware of their disease burden only after adhering to a gluten-free diet for some time,” the study says.

The authors describe it as the largest screening study that includes biopsy-confirmed diagnosis and follow-up on the gluten-free diet along with the use of immunohistochemical examination. The study points to reduced gluten consumption as a perceived healthier way of eating and without a celiac disease diagnosis as potentially leading to fewer characteristic signs of intestinal damage that would be determined through a biopsy. The immunohistochemical examination could improve accuracy of a diagnosis in the case, the study says.

Study limitations include lack of a control group in the gluten-free diet follow-up portion. Additionally, there is the potential that some participants reduced the amount of gluten they consumed prior to their biopsy even though they were advised not to do so. In that case, the immunohistochemical examination would have helped reduce the impact on study results, the authors note.

There is a general lack of accepted celiac disease screening criteria and scientific doubts about whether the gluten-free diet would improve what is often considered asymptomatic celiac disease, the authors note. And a gluten-free diet can be challenging to follow for those diagnosed through screening with only vague symptoms.

However, the study showed that about 1 percent of the adult population had undiagnosed celiac disease, and more importantly, the majority of screen-detected celiac disease patients improved on a gluten-free diet, the authors conclude.

“Screening of either high-risk groups or individuals with abdominal symptoms may not be sufficient to identify the majority of patients,” the study says. “Screening of the general population may be the only way to identify the majority of untreated celiac disease patients.”

Additionally, physicians should test for celiac disease even in the absence of abdominal complaints “because most adult patients appear to consider their symptoms a part of their normal state and, therefore, remain untested and undiagnosed,” the study suggests.

Screening for celiac disease in the US

In 2017, the U. S. Preventative Services Task Force concluded there is insufficient evidence to assess the balance of benefits and harms of screening for celiac disease in those who do not have symptoms. The task force is a panel of experts in disease prevention that works to improve the health of Americans by making evidence-based recommendations about clinical preventive services.

A subsequent study of nearly 10,000 children in Colorado concluded that universal screening may be the only way to identify all the children in the United States who have celiac disease.

The study by researchers at University of Colorado also found that symptoms were not reliable predictors of which children would have celiac disease. And most children who had positive antibody screening did not have a family history of celiac disease.

In the first study of its kind in the United States, Marisa Gallant Stahl, MD, of Children’s Hospital Colorado, set out evaluate the impact of celiac disease on the health and quality of life of children who were identified through an earlier mass-screening program. The research is being funded by Beyond Celiac and Stahl recently updated its progress at the Beyond Celiac Research Summit

In the screening of 10,000 children, 242 or 2.4 percent, had an initial positive celiac disease test. Of the 185 children who returned for follow-up, 149 had a positive confirming test. Of those, 62 were seen by a gastroenterologist and 39 went on to be diagnosed with celiac disease. Since these children had no obvious symptoms of celiac disease, they would be unlikely to be diagnosed otherwise, said Stahl.

You can read more about the Norwegian study here.

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