Utility of indices using C-peptide levels for indication of insulin therapy to achieve good glycemic control in Japanese patients with type 2 diabetes.
Aims/Introduction:  Type 2 diabetes is progressive in that therapy must be altered over time, which is partly as a result of the progressive loss of pancreatic β-cell function. To elucidate the relationship between residual endogenous insulin secretion and the necessity of insulin therapy to achieve good glycemic control, indices using serum C-peptide immunoreactivity (CPR) were analyzed in patients with type 2 diabetes.


METHODS
The data of 201 Japanese patients with type 2 diabetes who achieved the target of glycemic control during admission were analyzed retrospectively. Indices using CPR including fasting CPR (FCPR), CPR 6 min after intravenous injection of glucagon (CPR-6 min), increment of CPR (ΔCPR), secretory unit of islet in transplantation index (SUIT) and C-peptide index (CPI) were compared between the group requiring insulin (insulin group) and the group not requiring insulin (non-insulin group). A receiver-operator characteristic (ROC) curve was made, and optimal cut-off point and likelihood ratio were determined for each index.


RESULTS
All indices of CPR were lower in the insulin group compared with those in the non-insulin group. Likelihood ratios at the optimal point of FCPR, CPR-6 min, ΔCPR, SUIT, and CPI were 2.0, 2.1, 1.6, 2.3 and 2.8, respectively. Optimal cut-off point of CPI was 1.1 ng/mg. Sensitivity and specificity at optimal point of CPI were 61 and 78%, respectively.


CONCLUSIONS
The advantage of CPI of the indices of CPR to select insulin therapy to achieve good glycemic control was shown, but limitations of the predictive abilities of the indices using CPR should be taken into account. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00096.x, 2011).
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Shogo
S
Funakoshi
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Shimpei
S
Fujimoto
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Akihiro
A
Hamasaki
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Hideya
H
Fujiwara
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Yoshihito
Y
Fujita
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Kaori
K
Ikeda
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Shiho
S
Takahara
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Kazuaki
K
Nagashima
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Masaya
M
Hosokawa
Kansai Electric Power Hospital, Osaka, Japan.
Yutaka
Y
Seino
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Nobuya
N
Inagaki
C‐peptide; Glycemic control; Insulin therapy