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Rare and Atypical Diabetes Network (RADIANT)

The Rare and Atypical DIAbetes NeTwork (RADIANT) is a multicenter prospective cohort study that is dedicated to characterizing (discovering and defining) rare and atypical forms of diabetes. Individuals will be screened for evaluation of suspected atypical diabetes of unknown origin. Among the pool of evaluated individuals, those found to have a known form of diabetes will be excluded from further study. The remaining participants will be prioritized for genetic/genomic analysis and further testing.

Primary Objectives:

• Identify and enroll individuals and families with undiagnosed rare and atypical forms of diabetes.

• Determine the etiologic basis of the metabolic disorder among individuals and families with novel forms of rare and atypical diabetes.

• Understand the pathophysiology of individuals and families with novel forms of rare and atypical forms of diabetes.

RADIANT has three distinct stages.

Stage 1: Participants complete a consent form and a questionnaire to determine the potential for having atypical forms of diabetes. Participants identified as potentially having atypical forms of diabetes based on questionnaire responses are asked to provide a blood sample to test for islet autoantibodies and complete additional questionnaires.

The RADIANT Adjudication Committee, which is comprised of a team of experts in diabetes, assesses the data collected in Stage 1, then selects and prioritizes participants to proceed to Stage 2 and 3 for Whole Genome Sequencing (WGS) and other testing.

Stage 2: Genetic screening of participants for known forms of monogenic diabetes. Participants will consent for this stage of the study, complete a family history questionnaire, and have blood collected for DNA and RNA extraction, storage, and analysis. Whole genome sequencing (WGS) is performed on all DNA samples. If WGS does not identify a pathogenic/likely pathogenic variant in a known monogenic diabetes gene that is thought to explain the participant's diabetes, RNA Sequencing is performed at Baylor College of Medicine.

Stage 3: Deeper phenotyping of all participants who proceed to Stage 3. Participants visit a study clinic to consent and complete Stage 3 procedures which include: an Oral Glucose Tolerance Test (OGTT), additional blood collection, a detailed physical exam, and additional questionnaires.

The work of the Discovery Team is expected to be an iterative process analyzing all data collected up to this point in the study to understand the significance of novel variants. In some instances, the Discovery Team may determine that enrollment of the Proband's family members is necessary.

Family members with suspected atypical diabetes will follow the same study procedures as described above. Affected and unaffected family members may also be enrolled for Sanger Sequencing or trio WGS. The Discovery Team may also recommend additional optional procedures to better characterize the participant's form of diabetes.

Clinical and deeper phenotyping data can be requested from the NIDDK Central Repository (https://doi.org/10.58020/1wxp-dw53).