Table 1

Regression models of analysis of predictors for stimulated C-peptide or HbA1c over time and correlation between peak C-peptide and IDAA1C over time by age

Estimates from regression models with stimulated peak C-peptide
Age (P value)Sex (P value)HbA1c (P value)Insulin (P value)BMI Z (P value)Baseline C-peptide (P value)R2
Log(stimulated C-peptide)
 6 months (n = 372)0.005 (0.19)−0.07 (0.23)−0.18 (<0.0001)−0.81 (<0.0001)0.009 (0.77)0.90 (<0.0001)0.58
 12 months (n = 370)0.01 (0.06)−0.13 (0.14)−0.19 (<0.0001)−0.90 (<0.0001)0.004 (0.92)1.22 (<0.0001)0.52
 24 months (n = 299)0.03 (0.003)−0.08 (0.54)−0.18 (0.0002)−0.97 (<0.0001)−0.01 (0.88)1.58 (<0.0001)0.46
 36 months (n = 73)0.02 (0.30)0.01 (0.96)−0.23 (0.03)−1.04 (0.06)−0.09 (0.60)1.76 (<0.0001)0.44
 48 months (n = 43)0.01 (0.62)0.02 (0.97)−0.27 (0.03)−0.69 (0.36)−0.09 (0.59)2.70 (<0.0001)0.52
Estimates from regression models with HbA1c
Age (P value)Sex (P value)Log(stimulated C-peptide) (P value)Insulin (P value)BMI Z (P value)Baseline HbA1c (P value)R2
HbA1c
 6 months (n = 354)−0.02 (0.004)−0.06 (0.58)−0.55 (<0.0001)0.56 (0.02)0.08 (0.15)0.16 (0.001)0.33
 12 months (n = 354)−0.02 (0.002)−0.09 (0.49)−0.28 (<0.0001)0.76 (0.001)0.08 (0.21)0.19 (0.0007)0.28
 24 months (n = 285)−0.03 (0.02)−0.05 (0.80)−0.16 (0.02)0.66 (0.02)0.009 (0.92)0.15 (0.04)0.16
 36 months (n = 73)−0.03 (0.21)−0.42 (0.23)−0.12 (0.32)1.42 (0.02)0.16 (0.37)0.29 (0.12)0.30
 48 months (n = 43)−0.06 (0.15)0.05 (0.93)−0.09 (0.67)1.02 (0.35)−0.04 (0.86)0.21 (0.46)0.19
Correlation between peak C-peptide and IDAA1C over time by age
Duration of diabetes (years)Peak C-peptide ≥0.2 nmol/LIDAA1C* ≤9Correlation coefficient (P value)
% (95% CI)% (95% CI)
At 1 year
 <1271.2 (62.1, 78.5)29.0 (21.1, 37.3)−0.55 (<0.0001)
 12–1785.7 (79.4, 90.2)29.7 (23.0, 36.7)−0.69 (<0.0001)
 ≥1894.7 (88.5, 97.6)63.7 (53.9, 71.9)−0.68 (<0.0001)
At 2 years
 <1242.8 (33.4, 51.8)9.8 (5.2, 16.0)−0.24 (0.03)
 12–1765.3 (57.4, 72.1)13.2 (8.6, 18.8)−0.45 (<0.0001)
 ≥1880.5 (71.6, 86.8)52.9 (43.0, 61.8)−0.65 (<0.0001)
At 3 years
 <1226.9 (17.6, 37.1)−0.41 (0.05)
 12–1736.4 (27.9, 45.0)6.3 (3.0, 11.2)−0.48 (0.003)
 ≥1864.0 (52.6, 73.4)39.1 (28.8, 49.2)−0.72 (<0.0001)
At 4 years
 <129.6 (3.1, 20.5)−0.06(0.85)
 12–1727.0 (18.5, 36.1)2.7 (0.8, 6.8)−0.34(0.18)
 ≥1861.2 (48.9, 71.4)20.4 (9.2, 34.8)−0.70 (0.003)
  • *IDAA1C = HbA1c (percentage) + 4 × (insulin dose [in units/kg/day]).