Most Black People with Biopsy Confirmed Celiac Disease Have Negative TTG Blood Test Results

Celiac.com 08/15/2022 - In a significant finding, a celiac disease registry at University of Alabama reveals significant issues in accurately testing Black people for celiac disease using the TTG antibody test. The new registry of celiac disease patients at the University of Alabama at Birmingham is the work gastroenterologist Dr. Amanda Cartee, MD, and fellow colleagues at UAB.

Among the most important findings, the registry reveals that Black people with biopsy confirmed celiac disease are exponentially more likely than non-Hispanic whites to show negative results on the most common diagnostic celiac disease blood test. 

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For people with celiac disease, a positive TTG antibody test is the most common path to an endoscopy and biopsy to confirm or negate celiac disease.

For most people with celiac disease, especially non-Hispanic whites, a positive TTG test is highly predictive of celiac disease, hence the routine endoscopy and biopsy to follow-up a positive test. In fact, less than ten percent of non-Hispanic whites with biopsy-proven celiac disease have a "negative" TTG test. However, according to the registry data, high percentages of Black people with celiac disease are testing negative for TTG antibodies, and so being denied a swift and properly diagnosis, simply because they never meet themes common threshold for biopsy.

It's the TTG threshold currently used to determine the definition of positive and negative TTG that might just be at the heart of the problem. 

That's because the numbers are nearly reversed for Black people. While less than ten percent of non-Hispanic whites with celiac disease show negative TTG results, the registry data shows that a whopping eighty percent of Black people with biopsy-proven celiac disease have a "negative" TTG test. The means that these folks were unlikely to have gotten a biopsy as quickly as someone with a positive TTG test.

It also means they may have had to suffer longer, and/or self diagnose. And those facts are also borne out by the registry data, which point to longer times to diagnosis and less biopsy-driven diagnoses for Black celiac patients. Black patients were also much less likely to have received genetic testing for celiac-associated genes.

There is limited data on celiac disease and Black people, said Dr. Cartee, noting that only a single study with the primary goal of investigating the clinical characteristics of celiac disease and Black people has been done.

While the registry revealed differences in TTG test results and BMI, it showed similarities in celiac disease diagnosis for non-Hispanic white and Black patients.  These included symptoms as the primary cause for testing, length of time to diagnosis, and a diagnosis that did not include recommended blood tests and a biopsy.

Basically, the data show that TTG tests will be negative in the vast majority of Black patients with biopsy-proven celiac disease. That means further study is needed to determine whether the TTG test is useful for Black patients, and more research needs to be done to figure out how to make sure they can get quickly and properly diagnosed.

Stat tuned for more on this and related stories regarding celiac disease testing, screening, and diagnosis in Black people, and in other ethnic populations.

Read more about the celiac registry data and findings presented by UAB gastroenterologist Dr. Amanda Cartee, MD, at Digestive Disease Week.