Islet cell antibodies and fasting plasma C-peptide during the first 10 yr after diagnosis in patients with diabetes mellitus diagnosed in adult age

Abstract

Islet cell antibodies (ICA), fasting plasma C-peptide, and HbA(1c) were evaluated up to 10 years after diagnosis in 52 patients with diabetes diagnosed in adult age (mean age at diagnosis 53 ± 2 yr, range 21-76 yr) with a high (>20 IU/day) insulin requirement (group A) and in 50 matched control patients with diabetes diagnosed in adult age (mean age at diagnosis 54 ± 2 yr, range 24-73 yr) with low or no (<20 IU/day) insulin requirement (group B) during the first 3 yrs after diagnosis. Patients in group A showed a significantly higher frequency of ICA (37% [19/52] vs 10% [5/50]; p < 0.05), lower C-peptide (0.33 ± 0.06 nmol/l vs 0.56 ± 0.05 nmol/l; p < 0.001) and higher HbA(1c) (8.15 ± 0.35% vs 6.81 ± 0.25%; p < 0.01) values than group B patients. ICA positive group A patients (0.22 ± 0.06 nmol/l) showed significantly lower C-peptide values than ICA negative group A (0.40 ± 0.09 nmol/l; p < 0.05) patients. C-peptide values correlated with body mass index (BMI) in ICA negative patients both in group A (r = 0.66; p < 0.001) and in group B (r = 0.34; p < 0.05) but not in ICA positive group A patients in whom C-peptide values correlated with age (r = 0.48; p < 0.05). There was a correlation between HbA(1c) and C-peptide values in ICA negative (n = 78; r = -0.31; p < 0.01) but not in ICA positive patients (n = 24; r = -0.17; NS). ICA were most frequent in females (20/59 females vs 4/43 males; p < 0.01). ICA is associated with decreased pancreatic β-cell function in patients with diabetes diagnosed in adult age and may be detected up to 10 yr after diagnosis. Determination of ICA in patients with diabetes diagnosed in adult age improve the classification and etiological diagnosis of diabetes