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-
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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 FR 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 Download full-text
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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