Celiac Disease Screening Serology
A 9-month-old girl with trisomy 21 has had a weight plateau since 6 months of age, when wheat cereal was introduced, dropping from the 25th to below the 3rd percentile. Her parents describe three bulky pale stools daily. Examination shows a protuberant abdomen and wasted buttocks. Haemoglobin is 94 g/L with a mean corpuscular volume of 66 fL and ferritin 6 µg/L. Which is the most appropriate initial diagnostic test?
- A.Sweat chloride test
- B.Serum immunoglobulin levels
- C.Tissue transglutaminase IgA antibodyCorrect
- D.Duodenal biopsy
Explanation
Tissue transglutaminase IgA antibody, measured together with total serum IgA, is the recommended first-line screening test for celiac disease in a child with growth failure beginning after gluten introduction and iron deficiency anaemia refractory to diet. The antibody targets the enzyme that deamidates gliadin peptides, and its sensitivity and specificity both exceed 95 percent in IgA-sufficient children older than 2 years. Trisomy 21 is a recognised high-risk association, along with Turner syndrome, type 1 diabetes, autoimmune thyroiditis, and selective IgA deficiency, and screening is advised in these groups even when symptoms are subtle. Total IgA must accompany the tissue transglutaminase assay because selective IgA deficiency, which is over-represented in celiac disease, generates false negative results and mandates IgG-based testing such as deamidated gliadin peptide IgG. Endomysial antibody is highly specific but is more expensive and operator dependent, so it is used as a confirmatory rather than a screening test. Duodenal biopsy is the confirmatory step performed after positive serology and while the child still eats gluten, not the initial investigation. Sweat chloride testing screens for cystic fibrosis, which should be considered when malabsorption is accompanied by recurrent chest infections, and isolated immunoglobulin levels alone would not establish the diagnosis. Iron deficiency anaemia unresponsive to oral iron is a classic accompanying clue.
Why each option
- A.
- Sweat chloride testing is for cystic fibrosis, suggested by malabsorption plus chronic respiratory symptoms, which are absent here.
- B.
- Total IgA is measured alongside tissue transglutaminase to avoid false negatives, but immunoglobulin levels alone do not diagnose celiac disease.
- C.
- Correct. Tissue transglutaminase IgA with total IgA is the recommended initial screening test in suspected celiac disease.
- D.
- Duodenal biopsy confirms the diagnosis after positive serology; it is not the first-line initial test.
Reference: UpToDate 2025, Diagnosis of celiac disease in children
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