Celiac Disease ACG Guidelines Update

Celiac disease is a gluten-sensitive enteropathy, with a global pooled prevalence of 1.4%, which is increasing. Injury to the small bowel results in loss of absorptive surface area that translates into malabsorption of fat-soluble vitamins, iron, folic acid, and vitamin B12, which result in gastrointestinal and systemic symptoms. Here, we will review the updated recommendations of the American College of Gastroenterology (ACG) guidelines on the evaluation and management of celiac disease.

Patients with symptoms and signs of malabsorption, including chronic diarrhea with steatorrhea, weight loss, abdominal pain, and bloating, should be considered for celiac disease testing. The new guidelines suggest that those with a first-degree family member with confirmed diagnosed of celiac disease should also be considered for testing, regardless of whether they have symptoms. Screening in the general population is not recommended.

A combination of positive celiac serologies and small-bowel biopsies showing villous abnormalities are required to make the diagnosis of celiac disease. The sensitivity and specificity of tissue transglutaminase IgA (TTG-IgA) for untreated celiac disease is 95%, making it the serologic testing of choice. Because the prevalence of IgA deficiency in patients with celiac disease is as high as 2 - 3%, it is advisable to measure total IgA levels at the beginning of testing. If the levels of IgA are insufficient, an IgG-based test like deamidated gliadin peptide IgG or TTG-IgG would be the preferred serologic testing. For diagnosis, it is important to confirm that patients are incorporating gluten in their diet, as antibody-based testing is grounded on the intake of gluten.

For patients with positive serologies, EGD with duodenal biopsies is required to confirm the diagnosis.Those with a high clinical probability of celiac disease (>5%) and negative serology should undergo upper endoscopy with duodenal biopsies due to the possibility of seronegative celiac disease and for evaluation of other enteropathies. Obtaining 1 or 2 biopsies from the duodenal bulb and at least 4 biopsies from the post-bulbar duodenum is important for an adequate diagnosis as celiac disease can be patchy. The diagnosis is confirmed based on the presence of villous blunting, intraepithelial lymphocytosis, and crypt hyperplasia per the Marsh or simplified Corazza classification. Intraepithelial lymphocytosis (≥25/100 epithelial cells) alone is not specific for celiac disease, hence alternative diagnoses should be considered.

In cases of serology and histology discordance, testing for high-risk HLA haplotypes of celiac disease is helpful to clarify the diagnosis. If HLA-DQ2 and HLA-DQ8 are negative, the diagnosis of celiac disease can be safely ruled out. HLA-DQ2 and HLA-DQ8 also play a role when patients have already started a gluten-free diet on presentation. In those who are positive, a gluten challenge can be pursued.

In the case of children, a combination of elevated TTG IgA and a positive endomysial antibody (EMA) in a second blood sample is recommended to confirm the diagnosis. This approach is also reasonable for adult patients foregoing EGD, although the diagnosis would be deemed possible, instead of confirmed. For children younger than 2 years, the guidelines recommend a combination of TTG-IgA and deaminated gluten peptide (DGP)-IgG, as EMA IgA is less accurate in this population.

The only effective therapy for celiac disease is gluten-free diet (GFD). Due to the importance of adherence to a gluten-free diet, consultation with a dietitian is recommended after diagnosis. About 80% of individuals with celiac disease who are on a GFD will have a negative serology after 6 to 12 months. Although clinical improvement and normalization of antibodies suggest adherence to GFD, intestinal mucosal healing should be one of the end-point goals of therapy. As healing can take time, particularly in adults, the guidelines suggest a follow-up endoscopy with biopsy after 2 years of following a GFD. Lack of mucosal healing correlates with lymphoproliferative malignancy, bone disease, and refractory celiac disease. In the case of asymptomatic children following a GFD, follow-up biopsies are not recommended.

Although multiple tools to detect gluten in food have come to the market recently, data is lacking about their impact on clinical outcomes and adherence to GFD. Hence, the guidelines suggest against gluten detection devices.

Although dysbiosis is present in patients with celiac disease, there is not enough data to support the use of probiotics. Although oat consumption is safe in most patients with celiac disease, some might react to the oat protein itself, and there is risk of contamination with wheat. Hence, the guidelines suggest consuming gluten-free oats.

Patients with celiac disease are at higher risk of pneumococcal infections compared with the general population, which is due to functional hyposplenism. Hence, the ACG guidelines recommend vaccination against pneumococcus after diagnosis as part of the preventative care of patients with celiac disease. For adults without previous vaccination, the ACG suggests 1 dose of PCV20 (pneumococcal conjugated vaccine 20) alone or 1 dose of PCV15, followed by 1 dose of PPSV23 (pneumococcal polysaccharide vaccine 23).

Measurement of bone density with dual-energy X-ray absorptiometry should also be considered.

The updated guidelines provide new recommendations about considering testing asymptomatic first-degree relatives of confirmed individuals with celiac disease, correlation between serologic and endoscopic diagnosis in children and adults, the role of mucosal healing, the lack of evidence of tools to detect gluten, and probiotics. It also highlights the importance of preferring gluten-free oats, and of preventative immunization and measurement of bone density. As research evolves in this field that affects an increasing number of individuals, more data will be available to facilitate their diagnosis, adherence to gluten-free diet, and preventative care.

Reference

^{Rubio-Tapia, Alberto MD1; Hill, Ivor D. MD2; Semrad, Carol MD3; Kelly, Ciarán P. MD4; Greer, Katarina B. MD, MS5; Limketkai, Berkeley N. MD, PhD, FACG6; Lebwohl, Benjamin MD, MS7. American College of Gastroenterology Guidelines Update: Diagnosis and Management of Celiac Disease. The American Journal of Gastroenterology 118(1):p 59-76, January 2023. | DOI: 10.14309/ajg.0000000000002075}