Objective: To investigate the prevalence of first-degree relatives (FDRs) with celiac disease detected at screening and diagnostic significance of anti-tissue transglutaminase (anti-TTG). Patients and Methods: We performed a retrospective cohort study of 104 patients with a diagnosis of celiac disease and their FDRs, collecting data from electronic records of Mayo Clinic and celiac disease registry from December 20, 1983, to May 22, 2017. We collected demographics, presenting symptoms, indication for testing, family history, number of other family members screened, biopsy reports, and results of serologic tests. Results: Of 477 FDRs identified, 360 were screened (mean screening rate per family, 79%±25%) and 160 FDRs (44.4%) were diagnosed with celiac disease, at a mean age 31.9±21.6 years (62% female). All diagnosed FDRs had positive anti-TTG titers. Clinical features were documented in 148 diagnosed FDRs, of those 9 (6%) had classic, 97 (66%) had non-classic symptoms, and 42(28%) had no reported symptoms. Histology reports were available from 155 FDRs: 12 (8%) had Marsh 1, 77 (50%) had Marsh 3a, and 66 (43%) had Marsh 3b. A level of anti-TTG greater than or equal to 2.75 of the upper limit of normal identified FDRs with villous atrophy with 87% sensitivity, 82% specificity, and a positive predictive value of 95%. Conclusion: In a retrospective cohort study of patients diagnosed with celiac disease, we found a high prevalence of celiac disease among screened FDRs. High anti-TTG titers associated with villous atrophy on small bowel biopsies, irrespective of symptoms.
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