B-092 Effect of the Increased Specificity in a Recombinant anti-tTG Assay on a Celiac Disease Diagnostic Algorithm

Abstract

Abstract Background Celiac disease is an autoimmune disease where ingestion of gluten results in damage in the small intestine. Celiac disease is estimated to affect 1 in 100 people worldwide, but only 30% of individuals are correctly diagnosed. If celiac disease is neither diagnosed nor treated, this can lead to additional health problems such as type 1 diabetes, multiple sclerosis, short stature, coronary artery disease and small intestine cancers. The celiac disease diagnostic algorithm at our institution begins with determination of IgA levels in the patient. If the patient is not IgA deficient (IgA > 7 mg/dL), an anti-tissue transglutaminase (anti-tTG) IgA level is determined. In patients who have anti-tTG IgA ≥ 4U/mL, an endomysial antibodies (EMA) IgA is performed by indirect immunofluorescence (IFA). Inova Diagnostics updated the reagent from human-derived native antigen to a more specific assay containing a recombinant antigen. We investigated the impact of this change on the downstream testing in our algorithm. Methods The new assay was implemented in August of 2023, and the monthly test counts and percentage of abnormal results were counted for both anti-tTG IgA and EMA IFA before and after the new assay was implemented. Results As shown in Figure 1., switching to the new recombinant anti-tTG reagent resulted in a decrease in the number of anti-tTG IgA results that were classified as abnormal. Subsequently, the abnormal samples that advanced in the algorithm for EMA IFA testing had a higher percentage of abnormal results, while the number of tests performed was lower. Conclusions Use of a more specific anti-tTG assay results in reduction of false positive results, and tests that continue through the celiac disease algorithm are more likely to represent a true diagnosis of celiac disease.