Prevalence of residual B-cell function related to age at onset and genetic profile in newly diagnosed type I diabetics.

Patients with type I (insulin-dependent) diabetes mellitus maintain B-cell function for a varying period of time after onset. This is commonly held to account for post-initial remission. To estimate residual B-cell function we measured plasma and 24-h urinary C-peptide in 68 type I diabetic patients (age range 4-35 years, within 10-180 days of the onset of symptoms, typed for HLA-A, -B, -C and DR loci. A positive correlation (r = 0.26; p less than 0.05) was found between urinary C-peptide levels and the age of the patient. The analysis of variance of urinary C-peptide values on the basis of the presence or absence of DR3 and DR4 antigens revealed that the DR3-positive patients had reduced excretion (15.2 +/- 9.2 SD micrograms/24h) with respect to the others (22.7 +/- 15.5 SD micrograms/24h) (F = 6.35; p less than 0.05). No interaction effect was found in DR3/4 positive patients. Hence, late onset patients appear to have higher residual C-peptide secretion. In the light of these findings, the assessment of B-cell function and genetic profile may be useful in predicting which patients are likely to have remission periods and identifying the metabolic consequences of even minimal endogenous insulin secretion.