Stimulated beta-cell function separates high-risk from low-risk single-autoantibody relatives

Design

Prospective natural-history cohort analysis (TrialNet Pathway to Prevention), Cox and random forest models

Population

First- and second-degree relatives of people with type 1 diabetes, confirmed single islet autoantibody positive

Primary outcome

Progression to multiple autoantibodies or stage 3 type 1 diabetes

Effect

Combined stimulated glucose and C-peptide measures consistently predicted progression; subsets with >50% two-year and <10% five-year progression identified

TrialNet's Pathway to Prevention study screens first- and second-degree relatives of people with type 1 diabetes for islet autoantibodies. This analysis followed those confirmed positive for a single autoantibody, a group whose risk of progressing to multiple autoantibodies or clinical (stage 3) type 1 diabetes varies widely.

Metabolic function varied widely too. Measures that combined OGTT-stimulated glucose with stimulated C-peptide, as an index of beta-cell dysfunction, were consistently associated with progression across age groups (0 to 8, 8 to 16, 16 and over) and antibody types. Traditional risk factors, glucose or C-peptide alone and insulin-resistance indices behaved inconsistently. Data-derived cut-offs identified small subsets with more than 50% two-year progression and large groups with under 10% five-year progression.

The practical message is that a single antibody is not one risk category. A stimulated OGTT can help decide who needs close surveillance, and who might be considered for disease-modifying therapy trials; the authors suggest lower-risk relatives may need less intensive surveillance, but the cut-offs are unvalidated.

• A relative with one islet autoantibody is not uniformly low risk; a small subset progresses within two years.
• An OGTT with both glucose and C-peptide measured is more informative than fasting glucose or HbA1c alone in this group.
• Age and antibody type still matter; interpret metabolic results alongside them.
• Large low-risk groups (<10% at five years) were identified, but the cut-offs are unvalidated; keep standard monitoring for autoantibody-positive relatives.

Why it matters

Single-autoantibody positivity is often filed as low risk; this shows a hidden high-risk subset that metabolic testing can find.

Don't overread it

The cut-offs are data-driven and have not been validated in an independent cohort.

The statistics, in plain English

The cut-offs were derived from the same data they were tested on, so their performance is likely to look better here than it will in a new population. The risk figures (over 50% at two years, under 10% at five years) describe groups, not individual certainty.

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