Fig. 2
Adapted from Canadian Celiac Association Professional Advisory Council [20]
Algorithm for the evaluation and diagnosis of celiac disease. CD occurs in 2–5% of people with selective IgA deficiency. All symptomatic IgA deficient patients should be referred for endoscopic small intestinal biopsies regardless of their serology results, as false negatives can occur. In asymptomatic individuals with IgA deficiency, the laboratory may be able to perform IgG-TTG or an IgG-deamidated gliadin peptide (IgG-DGP). Negative HLA-DQ2 or DQ8 genetic tests are helpful to exclude the diagnosis of CD because over 99% of patients with CD are positive for HLA-DQ2 or DQ8. However, approximately 30% of the general population tests positive for one of these HLA types and most do not develop CD. IgA immunoglobulin A, TTG tissue transglutaminase antibody, EMA endomysium antibody, HLA human leukocyte antigens