IDAA1c of 9 or less misses partial remission in youth with overweight

Design

Diagnostic accuracy analysis within a prospective cohort

Population

422 youth with type 1 diabetes, stimulated C-peptide within 12 months of diagnosis

Primary outcome

Accuracy of IDAA1c ≤9 for C-peptide-defined partial remission

Effect

Sensitivity 61%, specificity 79%, AUC 0.77 overall; sensitivity 45% in overweight or obesity

Investigators in the SEARCH for Diabetes in Youth study took 422 young people with type 1 diabetes who had a mixed-meal stimulated C-peptide measured within a year of diagnosis. They compared the familiar insulin dose-adjusted HbA1c (HbA1c plus four times the daily insulin dose per kg) against a C-peptide definition of partial remission.

The score behaved oddly by weight. Children with normal weight had a lower IDAA1c than those with overweight or obesity (8.95 v 9.28) even though their stimulated C-peptide was lower (1.25 v 1.88 ng/mL). Insulin resistance inflates the insulin dose, and the dose term inflates the score, so heavier children with more residual beta-cell function look as though they are not in remission.

Overall, IDAA1c of 9 or less picked up 61% of those with remission and correctly excluded 79% of those without. In the overweight group sensitivity fell to 45%. Raising the cut-off to 11.6 in that group caught 93% but specificity dropped to 54%.

In clinic this matters mainly when a family asks whether the honeymoon is ending, and when screening children for disease-modifying trials. The score is a convenience, not a measure of beta-cell function; where the answer changes a decision, a stimulated C-peptide is the better test.

• Treat an IDAA1c above 9 in a child with overweight as uninformative about remission, not as proof it has ended.
• Where remission status changes a decision, such as trial eligibility, consider a stimulated C-peptide instead.
• Record weight centile alongside IDAA1c when you document the honeymoon phase.
• Rising insulin needs in a heavier child may reflect insulin resistance as much as falling beta-cell reserve.

Why it matters

A score used to select children for disease-modifying trials systematically under-reads beta-cell function in the heavier ones.

Don't overread it

This is a US cohort within 12 months of diagnosis; the alternative cut-off of 11.6 has not been tested in a separate group.

The statistics, in plain English

Sensitivity of 45% means that of every 20 overweight children who truly had partial remission by C-peptide, the score flagged only about 9. An area under the curve of 0.77 is fair, not good: a coin toss scores 0.5 and a perfect test 1.0. Moving the cut-off to 11.6 trades misses for false alarms — sensitivity rose to 93% but nearly half of those without remission were then wrongly labelled as in it.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.