Autoimmune serology
Tissue transglutaminase IgAtTG-IgA
First-line celiac disease serology; high sensitivity and specificity on a gluten-containing diet.
Sample
Serum
Clinical reference range
— to 4 U/mL
Negative
Conv: —–4 U/mL
Biology
What it measures
IgA against tissue transglutaminase, the enzyme that deamidates gliadin in the gut mucosa.
Pitfalls
Pre-analytic & interpretation traps
- !Always co-order total IgA — selective IgA deficiency (1:500) gives false negatives. Switch to DGP-IgG or tTG-IgG if deficient.
- !Patient must be on a gluten-containing diet for ≥6 weeks before testing.
- !tTG-IgA ≥10× ULN + positive EMA-IgA may permit no-biopsy diagnosis in children (ESPGHAN).
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