In October 2019, the European Society for Paediatric Gastroenterology, Hepatology and Nutrition published guidelines for the diagnosis of celiac disease.
There is no need for HLA-DQ2 and HLA-DQ8 typing in patients with positive transglutaminase immunoglobulin A (TGA-IgA) if they qualify for celiac disease (CD) diagnosis with biopsies or if high serum TGA-IgA (≥10 times the upper limit of normal [ULN]) and endomysial antibody (EMA)-IgA positivity exist. While patients testing negative for HLA-DQ2 and HLA-DQ8 have a very low CD risk, the diagnosis is not confirmed with a positive result.
If serum IgA values are normal for age, TGA-IgA should serve, regardless of patient age, as the initial serologic test.
Children with suspected CD should undergo total IgA and TGA-IgA testing as an initial screen. If total IgA concentrations are low, the second step should consist of an IgG-based test (deamidated gliadin peptide [DGP], EMA, or TGA). Testing for EMA, DGP, or AGA antibodies (IgG and IgA) is not recommended as an initial screen in clinical practice.
The TGA-IgA serum concentration should be at least 10x ULN for a diagnosis of CD made without biopsies. Antibody tests should be used only if they have proper calibration curve–based calculation and their measurement range accommodates a 10x ULN value. In patients in whom IgA is deficient but IgG-based serologic tests are positive, biopsies should not be omitted.
If the parents/patient have agreed to a no-biopsy approach to CD diagnosis, a positive EMA-IgA test performed on a second blood sample should be used to confirm the diagnosis in children with TGA ≥10x ULN.
While the patient is on a gluten-containing diet, histologic evaluation should be carried out using at least four biopsies from the distal duodenum and at least one from the duodenal bulb. Optimally orientated biopsies should be assessed. The presence of mucosal lesions is indicated by a villous-to-crypt ratio of less than 2. If the TGA results are discordant with the histopathology, the biopsies should be recut and/or a second opinion should be obtained from an experienced pathologist.
It is not necessary to consider that other pathologies or diagnoses may have been missed if the CD diagnosis omits upper endoscopy with biopsies.
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Cite this: Celiac Disease Diagnosis Clinical Practice Guidelines (2019) - Medscape - Oct 29, 2019.