Index60 as an additional diagnostic criterion for type 1 diabetes

Area of Science:

• Endocrinology
• Metabolic Diseases
• Diabetes Research

Background:

• Type 1 diabetes (T1D) diagnosis relies on specific criteria, but individuals in peri-diagnostic ranges require further characterization.
• The Index60, a composite measure of glucose and C-peptide, is explored as a potential indicator in T1D prediction.

Purpose of the Study:

• To compare the characteristics of autoantibody-positive individuals identified by elevated 2-hour oral glucose tolerance test (OGTT) glucose, elevated Index60, or both.
• To assess the progression to diabetes in these distinct groups.

Main Methods:

• Analysis of 354 autoantibody-positive participants from the Type 1 Diabetes TrialNet Pathway to Prevention study.
• Categorization into three groups based on baseline OGTT: elevated glucose only [Glu(+)], elevated Index60 only [Ind(+)], or both [Glu(+)/Ind(+)].
• Comparison of demographic, metabolic (C-peptide, glucose), and immunological (autoantibodies) characteristics and diabetes progression rates.

Main Results:

• The Glu(+) group was older, had higher C-peptide responses and BMI, and lower multiple autoantibody positivity compared to Ind(+) and Glu(+)/Ind(+) groups.
• Both Glu(+) and Ind(+) groups showed high progression to diabetes (61% and 63%, respectively).
• The Ind(+) group, despite not meeting standard diagnostic criteria at baseline, had a 4-year cumulative diabetes incidence of 95%.

Conclusions:

• Individuals identified by elevated Index60 (Ind(+)) exhibit more typical type 1 diabetes characteristics and a high likelihood of diagnosis.
• Elevated Index60 is a strong predictor of type 1 diabetes, even when not identified by standard OGTT criteria.
• The findings highlight the utility of Index60 in identifying individuals at high risk for type 1 diabetes who might otherwise be missed at baseline screening.