Site-specific risks
In the HLA, sex, and family-adjusted model, Colorado children had a 2.5-fold higher risk of CD, compared with Washington children. Likewise, Swedish children had a 1.8-fold higher risk of CD than children in Germany, a 1.7-fold higher than children in the United States, and a 1.4-fold higher risk than children in Finland.
Among DQ2.5 participants, Sweden demonstrated the highest risk, with 63.1% of patients developing CDA by age 10 and 28.3% developing CD by age 10. Finland consistently had a higher incidence of CDA than Colorado, at 60.4% versus 50.9%, for DQ2.5 participants but a lower incidence of CD than Colorado, at 20.3% versus 22.6%.
The research team performed a post hoc sensitivity analysis using a lower tTGA cutoff to reduce bias in site differences for biopsy referral and to increase sensitivity of the CD definition for incidence estimation. When the tTGA cutoff was lowered to an average two-visit tTGA of 67.4 or higher, more children met the serologic criteria for CD.
“Even with this lower cutoff, the differences in the risk of CD between clinical sites and countries were still observed with statistical significance,” the authors write. “This indicates that the regional differences in CD incidence could not be solely attributed to detection biases posed by differential biopsy rates.”
Multiple environmental factors likely account for the differences in autoimmunity among regions, the authors write. These variables include diet, chemical exposures, vaccination patterns, early-life gastrointestinal infections, and interactions among these factors. For instance, the Swedish site has the lowest rotavirus vaccination rates and the highest median gluten intake among the TEDDY sites.
Future prospective studies should capture environmental, genetic, and epigenetic exposures to assess causal pathways and plan for preventive strategies, the authors write. The TEDDY study is pursuing this research.
“From a policy standpoint, this informs future screening practices and supports efforts toward mass screening, at least in some areas,” the authors write. “In the clinical setting, this points to the importance for clinicians to have a low threshold for CD screening in the appropriate clinical setting.”
The TEDDY study is funded by several grants from the National Institute of Diabetes and Digestive and Kidney Diseases, the National Institute of Allergy and Infectious Diseases, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institute of Environmental Health Sciences, the Centers for Disease Control and Prevention, and the Juvenile Diabetes Research Foundation. The authors have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.