Peninsula NIHR Clinical Research Facility, Peninsula Medical School, University of Exeter, Exeter, UK.
Diabet Med. 2011 Sep;28(9):1034-8. doi: 10.1111/j.1464-5491.2011.03272.x.
Serum C-peptide measurement can assist clinical management of diabetes, but practicalities of collection limit widespread use. Urine C-peptide creatinine ratio may be a non-invasive practical alternative. The stability of C-peptide in urine allows outpatient or community testing. We aimed to assess how urine C-peptide creatinine ratio compared with serum C-peptide measurement during a mixed-meal tolerance test in individuals with late-onset, insulin-treated diabetes.
We correlated the gold standard of a stimulated serum C-peptide in a mixed-meal tolerance test with fasting and stimulated (mixed-meal tolerance test, standard home meal and largest home meal) urine C-peptide creatinine ratio in 51 subjects with insulin-treated diabetes (diagnosis after age 30 years, median age 66 years, median age at diagnosis 54, 42 with Type 2 diabetes, estimated glomerular filtration rate > 60 ml min(-1) 1.73 m(-2) ).
Ninety-minute mixed-meal tolerance test serum C-peptide is correlated with mixed-meal tolerance test-stimulated urine C-peptide creatinine ratio (r = 0.82), urine C-peptide creatinine ratio after a standard breakfast at home (r = 0.73) and urine C-peptide creatinine ratio after largest home meal (r = 0.71). A stimulated (largest home meal) urine C-peptide creatinine ratio cut-off of 0.3 nmol/mmol had a 100% sensitivity and 96% specificity (area under receiver operating characteristic curve = 0.99) in identifying subjects without clinically significant endogenous insulin secretion (mixed-meal tolerance test-stimulated C-peptide < 0.2 nmol/l). In detecting a proposed serum C-peptide threshold for insulin requirement (stimulated serum C-peptide < 0.6 nmol/l), a stimulated (largest home meal) urine C-peptide creatinine ratio cut-off of 0.6 nmol/mmol had a sensitivity and specificity of 92%.
In patients with insulin-treated diabetes diagnosed after age 30 years, urine C-peptide creatinine ratio is well correlated with serum C-peptide and may provide a practical alternative measure to detect insulin deficiency for use in routine clinical practice.
血清 C 肽测定有助于糖尿病的临床管理，但采集的实际情况限制了其广泛应用。尿 C 肽肌酐比值可能是一种非侵入性的实用替代方法。C 肽在尿液中的稳定性允许门诊或社区检测。我们旨在评估尿 C 肽肌酐比值在接受混合餐耐量试验的迟发性、胰岛素治疗的糖尿病患者中与血清 C 肽测定的相关性。
我们将混合餐耐量试验中刺激后的血清 C 肽的金标准与 51 例胰岛素治疗的糖尿病患者的空腹和刺激后（混合餐耐量试验、标准家庭餐和最大家庭餐）尿 C 肽肌酐比值相关联。（诊断年龄>30 岁，中位年龄 66 岁，中位发病年龄 54 岁，42 例 2 型糖尿病，估计肾小球滤过率>60 ml min(-1) 1.73 m(-2)）。
90 分钟混合餐耐量试验血清 C 肽与混合餐耐量试验刺激后尿 C 肽肌酐比值相关（r = 0.82），与标准家庭早餐后尿 C 肽肌酐比值相关（r = 0.73），与最大家庭餐后尿 C 肽肌酐比值相关（r = 0.71）。刺激后（最大家庭餐）尿 C 肽肌酐比值截断值为 0.3 nmol/mmol 时，识别无临床显著内源性胰岛素分泌（混合餐耐量试验刺激后 C 肽<0.2 nmol/l）的患者的灵敏度为 100%，特异性为 96%（受试者工作特征曲线下面积=0.99）。在检测胰岛素需求的拟议血清 C 肽阈值时，刺激后（最大家庭餐）尿 C 肽肌酐比值截断值为 0.6 nmol/mmol 时，灵敏度和特异性分别为 92%。
在诊断年龄>30 岁的胰岛素治疗糖尿病患者中，尿 C 肽肌酐比值与血清 C 肽密切相关，可能为检测胰岛素缺乏提供一种实用的替代方法，用于常规临床实践。
