Urine C-peptide creatinine ratio is a noninvasive alternative to the mixed-meal tolerance test in children and adults with type 1 diabetes.
ABSTRACT Stimulated serum C-peptide (sCP) during a mixed-meal tolerance test (MMTT) is the gold standard measure of endogenous insulin secretion, but practical issues limit its use. We assessed urine C-peptide creatinine ratio (UCPCR) as an alternative.
Seventy-two type 1 diabetic patients (age of diagnosis median 14 years [interquartile range 10-22]; diabetes duration 6.5 [2.3-32.7]) had an MMTT. sCP was collected at 90 min. Urine for UCPCR was collected at 120 min and following a home evening meal.
MMTT 120-min UCPCR was highly correlated to 90-min sCP (r = 0.97; P < 0.0001). UCPCR ≥ 0.53 nmol/mmol had 94% sensitivity/100% specificity for significant endogenous insulin secretion (90-min sCP ≥ 0.2 nmol/L). The 120-min postprandial evening meal UCPCR was highly correlated to 90-min sCP (r = 0.91; P < 0.0001). UCPCR ≥ 0.37 nmol/mmol had 84% sensitivity/97% specificity for sCP ≥ 0.2 nmol/L.
UCPCR testing is a sensitive and specific method for detecting insulin secretion. UCPCR may be a practical alternative to serum C-peptide testing, avoiding the need for inpatient investigation.
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ABSTRACT: AIMS: To determine the prevalence and clinical characteristics of absolute insulin deficiency in long-standing Type 2 diabetes, using a strategy based on home urinary C-peptide creatinine ratio measurement. METHODS: We assessed the urinary C-peptide creatinine ratios, from urine samples taken at home 2 h after the largest meal of the day, in 191 insulin-treated subjects with Type 2 diabetes (diagnosis age ≥45 years, no insulin in the first year). If the initial urinary C-peptide creatinine ratio was ≤0.2 nmol/mmol (representing absolute insulin deficiency), the assessment was repeated. A standardized mixed-meal tolerance test with 90-min stimulated serum C-peptide measurement was performed in nine subjects with a urinary C-peptide creatinine ratio ≤ 0.2nmol/mmol (and in nine controls with a urinary C-peptide creatinine ratio >0.2nmol/mmol) to confirm absolute insulin deficiency. RESULTS: A total of 2.7% of participants had absolute insulin deficiency confirmed by a mixed-meal tolerance test. They were identified initially using urinary C-peptide creatinine ratio: 11/191 subjects (5.8%) had two consistent urinary C-peptide creatinine ratios ≤ 0.2 nmol/mmol; 9/11 subjects completed a mixed-meal tolerance test and had a median stimulated serum C-peptide of 0.18nmol/l. Five out of nine subjects had stimulated serum C-peptide <0.2 nmol/l and 9/9 subjects with urinary C-peptide creatinine ratio >0.2 had endogenous insulin secretion confirmed by the mixed-meal tolerance test. Compared with subjects with a urinary C-peptide creatinine ratio >0.2 nmol/mmol, those with confirmed absolute insulin deficiency had a shorter time to insulin treatment (median 2.5 vs. 6 years, P=0.005) and lower BMI (25.1 vs. 29.1kg/m(2) , P=0.04). Two out of five patients were glutamic acid decarboxylase autoantibody-positive. CONCLUSIONS: Absolute insulin deficiency may occur in long-standing Type 2 diabetes, and cannot be reliably predicted by clinical features or autoantibodies. Its recognition should help guide treatment, education and management. The urinary C-peptide creatinine ratio is a practical non-invasive method to aid detection of absolute insulin deficiency, with a urinary C-peptide creatinine ratio > 0.2nmol/mmol being a reliable indicator of retained endogenous insulin secretion. This article is protected by copyright. All rights reserved.Diabetic Medicine 05/2013; · 3.24 Impact Factor
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ABSTRACT: C-peptide is produced in equal amounts to insulin and is the best measure of endogenous insulin secretion in patients with diabetes. Measurement of insulin secretion using C-peptide can be helpful in clinical practice: differences in insulin secretion are fundamental to the different treatment requirements of Type 1 and Type 2 diabetes. This article reviews the use of C-peptide measurement in the clinical management of patients with diabetes, including the interpretation and choice of C-peptide test and its use to assist diabetes classification and choice of treatment. We provide recommendations for where C-peptide should be used, choice of test and interpretation of results. With the rising incidence of Type 2 diabetes in younger patients, the discovery of monogenic diabetes and development of new therapies aimed at preserving insulin secretion, the direct measurement of insulin secretion may be increasingly important. Advances in assays have made C-peptide measurement both more reliable and inexpensive. In addition, recent work has demonstrated that C-peptide is more stable in blood than previously suggested or can be reliably measured on a spot urine sample (urine C-peptide:creatinine ratio), facilitating measurement in routine clinical practice. The key current clinical role of C-peptide is to assist classification and management of insulin-treated patients. Utility is greatest after 3-5 years from diagnosis when persistence of substantial insulin secretion suggests Type 2 or monogenic diabetes. Absent C-peptide at any time confirms absolute insulin requirement and the appropriateness of Type 1 diabetes management strategies regardless of apparent aetiology. © 2013 The Authors. Diabetic Medicine © 2013 Diabetes UK.Diabetic Medicine 02/2013; · 3.24 Impact Factor
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ABSTRACT: Classically, type 1 diabetes is thought to proceed to absolute insulin deficiency. Recently developed ultrasensitive assays capable of detecting C-peptide under 5 pmol/l now allow very low levels of C-peptide to be detected in patients with long-standing type 1 diabetes. It is not known whether this low-level endogenous insulin secretion responds to physiological stimuli. We aimed to assess how commonly low-level detectable C-peptide occurs in long-duration type 1 diabetes and whether it responds to a meal stimulus. We performed a mixed-meal tolerance test in 74 volunteers with long-duration (>5 years) type 1 diabetes, i.e. with age at diagnosis 16 (9-23) years (median [interquartile range]) and diabetes duration of 30 (19-41) years. We assessed fasting and stimulated serum C-peptide levels using an electrochemiluminescence assay (detection limit 3.3 pmol/l), and also the urinary C-peptide:creatinine ratio (UCPCR). Post-stimulation serum C-peptide was detectable at very low levels (>3.3 pmol/l) in 54 of 74 (73%) patients. In all patients with detectable serum C-peptide, C-peptide either increased (n = 43, 80%) or stayed the same (n = 11) in response to a meal, with no indication of levels falling (p < 0.0001). With increasing disease duration, absolute C-peptide levels fell although the numbers with detectable C-peptide remained high (68%, i.e. 25 of 37 patients with >30 years duration). Similar results were obtained for UCPCR. Most patients with long-duration type 1 diabetes continue to secrete very low levels of endogenous insulin, which increase after meals. This is consistent with the presence of a small number of still functional beta cells and implies that beta cells are either escaping immune attack or undergoing regeneration.Diabetologia 10/2013; · 6.49 Impact Factor
Urine C-Peptide Creatinine Ratio Is a
Noninvasive Alternative to the
Mixed-Meal Tolerance Test in Children
and Adults With Type 1 Diabetes
RACHEL E.J. BESSER, MBBS1
JOHNNY LUDVIGSSON, PHD2
ANGUS G. JONES, MBBS1
TIMOTHY J. MCDONALD, MSC1,3
BEVERLEY M. SHIELDS, PHD1
BRIDGET A. KNIGHT, PHD1
ANDREW T. HATTERSLEY, DM1
is the gold standard measure of endogenous insulin secretion, but practical issues limit its use.
We assessed urine C-peptide creatinine ratio (UCPCR) as an alternative.
RESEARCH DESIGN AND METHODS—Seventy-two type 1 diabetic patients (age of
diagnosis median 14 years [interquartile range 10–22]; diabetes duration 6.5 [2.3–32.7]) had an
MMTT. sCP was collected at 90 min. Urine for UCPCR was collected at 120 min and following a
home evening meal.
RESULTS—MMTT 120-min UCPCR was highly correlated to 90-min sCP (r = 0.97; P ,
0.0001). UCPCR $0.53nmol/mmol had 94% sensitivity/100% specificity for significant endog-
enous insulin secretion (90-min sCP $0.2 nmol/L). The 120-min postprandial evening meal
UCPCR washighlycorrelated to 90-min sCP (r= 0.91;P, 0.0001). UCPCR$0.37 nmol/mmol
had 84% sensitivity/97% specificity for sCP $0.2 nmol/L.
CONCLUSIONS—UCPCR testing is a sensitive and specific method for detecting insulin
Diabetes Care 34:607–609, 2011
tion in type 1 diabetes, but practical
issues restrict testing to the hospital
setting (1,2). Ninety-minute stimulated
serum C-peptide (sCP) $0.2 nmol/L
($0.6 ng/L) is related to improved clini-
cal outcomes (3) and is used to indicate
significant endogenous insulin secretion
(4–6). We have recently shown urine
C-peptide creatinine ratio (UCPCR) to
be both reproducible and stable for
3 days at room temperature using boric
(MMTT) is the gold standard mea-
sure of endogenous insulin secre-
acid as a preservative (7). Here, we
assessed whether UCPCR is a noninva-
sive alternative to the 90-min sCP re-
sponse during the MMTT in type 1
RESEARCH DESIGN AND
about study design, ethical considerations,
and laboratory methods can be found in
Supplementary Materials. We studied 72
children (n = 21) and adults with type 1
diabetes without known renal impair-
ment (estimated glomerular filtration
rate ,60 mL/min/1.73 m2) (Supplemen-
tary Tables 1 and 2).
Patients underwent a standard MMTT
(1). sCP was collected at 0 and 90 min.
Additional samples were taken at 30, 60,
second morning void immediately before
the start of the MMTT (0 min) and after
Significant endogenous insulin secre-
tion was defined as 90-min sCP $0.2
nmol/L, in accordance with the Diabetes
Control and Complications Trial (8).
Home urine collections
Urine was collected in boric acid 120 min
after the evening meal following a pre-
meal void. Adult patients collected fur-
ther home urine samples 120 min after a
following the patients’ own lunch. Urine
frozen at 280°C.
We assessed the association between 90-
UCPCR and after the home evening meal
(Spearman rank correlation coefficient).
In the pediatric cohort, correlations
were also determined between AUC sCP
and 120-min UCPCR. UCPCR cutoffs
equivalent to 90-min sCP $0.2 nmol/L
were derived using linear regression equa-
tions. UCPCR (120 min) following a home
evening meal was compared with that
after a MMTT (Wilcoxon test for paired
UCPCR correlations with serum
MMTT 120-min UCPCR was highly cor-
related with the 90-min sCP (r = 0.97;
P , 0.0001). The equivalent 120-min
c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c
From the1Peninsula National Institute for Health Research Clinical Research Facility, Peninsula Medical
School, University of Exeter, Exeter, U.K.; the2Division of Pediatrics, Department of Clinical and Exper-
imental Medicine, Linköping University, Linköping, Sweden; and the
chemistry, Royal Devon & Exeter NHS Foundation Trust, Exeter, U.K.
Corresponding author: Andrew T. Hattersley, firstname.lastname@example.org.
Received 9 November 2010 and accepted 11 December 2010.
This article contains Supplementary Data online at http://care.diabetesjournals.org/lookup/suppl/doi:10.
R.E.J.B. and J.L. contributed equally to this study.
© 2011 by the American Diabetes Association. Readers may use this article as long as the work is properly
licenses/by-nc-nd/3.0/ for details.
3Department of Clinical Bio-
care.diabetesjournals.orgDIABETES CARE, VOLUME 34, MARCH 2011
C l i n i c a l C a r e / E d u c a t i o n / N u t r i t i o n / P s y c h o s o c i a l R e s e a r c h
B R I E F R E P O R T
MMTT UCPCR cutoff for significant en-
dogenous insulin secretion (90-min sCP
$0.2 nmol/L) was $0.53 nmol/mmol,
(Fig. 1A). A strong correlation was also
seen between AUC for sCP and 120-min
UCPCR during the MMTT (r = 0.96; P ,
Home postprandial evening meal
UCPCR (120 min) was well correlated
with 90-min sCP (r = 0.91; P , 0.0001)
(Fig. 1B). The equivalent UCPCR cutoff
was $0.37 nmol/mmol, with 84% sensi-
tivity and 97% specificity (Fig. 1B).
Using the UCPCR cutoff $0.53
nmol/mmol in the home evening meal
samples yielded lower levels of sensitivity
(71%) and specificity (97%) for signifi-
cant endogenous insulin secretion. This
as shown by the lower 120-min UCPCR
in the home postprandial samples than in
terquartile range 0.01–0.76] vs. 0.35
nmol/mmol [0.04–1.41]; P , 0.0001).
and children when analyzed separately
(Supplementary Tables 4 and 5). Result
tables for combined (Supplementary
Table 3) and separate analysis of adults
(Supplementary Table 4) and children
(Supplementary Table 5) are given in the
during an MMTT or after a home meal is
highly correlated with MMTT sCP.
UCPCR offers a sensitive and specific
method of detecting insulin secretion.
UCPCR as a practical alternative to
serum C-peptide measurement
Our results showed strong correlations
between stimulated UCPCR and serum
C-peptide (r = 0.91–0.97) during an
MMTT. UCPCR, while not superior, has
some clear practical advantages over sCP.
sCP requires separating the serum by
spinning rapidly and subsequent freezing
(2). This effectively limits testing to the
hospital setting. Because UCPCR is stable
at room temperature for 3 days in boric
be collected following a liquid mixed
meal or the patients’ own home meal
and a spot urine sample collected and
posted for analysis directly. This would
allow assessment to be done at home
and to be noninvasive—a particular ad-
vantage for children.
As would be predicted, UCPCR values
were lower after a meal compared with the
standard MMTT, and so a lower concen-
tration of UCPCR was required to suggest
slight loss of precision compared with the
standard MMTT needs to be balanced by
the practicality of this approach because it
would remove the need for inpatient test-
ing and allow widespread screening.
Other measures of urinary C-peptide
The strong correlation of UCPCR with
Figure 1—Scatter diagram showing the relationship between 90-min sCP and 120-min UCPCR
is equivalent to 90-min sCP $0.2 nmol/L (linear regression), with 94% sensitivity and 100%
specificity. B: 120-min postprandial UCPCR is well correlated with 90-min sCP in the MMTT
(r = 0.91). UCPCR $0.37 nmol/mmol is equivalent to 90-min sCP $0.2 nmol/L (linear re-
gression), with 84% sensitivity and 97% specificity.
DIABETES CARE, VOLUME 34, MARCH 2011 care.diabetesjournals.org
UCPCR: a noninvasive alternative to the MMTT
by previous studies that have shown that
timed measures of urinary C-peptide are a
useful marker of endogenous insulin se-
cretion (7,9–13). We used UCPCR to cor-
rect for dilution by measuring creatinine.
This allowed spot samples to be taken
rather than sampling over 24 h, in which
case complete collection is difficult. This
is similar to the practical reason why spot
albumin creatinine ratio is used as op-
posed to 24 h urine collections in the as-
sessment of renal protein excretion.
A strong correlation between AUC C-
peptide and 120-min UCPCR was dem-
onstrated (r = 0.96); however, numbers
were small (n = 18) and further work is
ited to patients who could void on de-
mand. The test can be difficult in young
children, especially those who are still in
nappies. Our results also only apply to
patients without renal impairment. Fur-
ther studies are needed to confirm our
findings in this subgroup.
The ease of use means that, if used in
conjunction with formal MMTT, UCPCR
may be useful for screening patients for
initial inclusion and also follow-up during
demonstrates that in children and adults
with type 1 diabetes, UCPCR may be a
practical noninvasive alternative to the
MMTT for use in routine clinical practice.
Acknowledgments—We acknowledge the
support of Diabetes UK for this project
through funding (through a clinical training
the Peninsula National Institute for Health
Research Clinical Research Facility and from
the European Community FP7 program
Collaborative European Effort to Develop
Diabetes Diagnostics (CEED3) (HEALTH-
F2-2008-223211). The study was also sup-
ported by Barndiabetesfonden (The Swedish
Child Diabetes Foundation) and the Swedish
No potential conflicts of interest relevant to
this article were reported.
R.E.J.B. researched data, contributed to
discussion, wrote the manuscript, and re-
viewed and edited the manuscript. J.L. re-
searched data, contributed to discussion, and
reviewed and edited the manuscript. A.G.J.
contributed to discussion and reviewed and
edited the manuscript. T.J.M., B.M.S., B.A.K.,
and A.T.H. researched data, contributed to
discussion, and reviewed and edited the
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