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Implications for the use of FPG and HbA1c for cost-effective screening
DAVID R. JESUDASON, MBBS, FRACP1
KERRIE DUNSTAN, RN1 DARRYL LEONG, MBBS1
GARY A. WITTERT, MBBCH, MD, FRACP1,2
OBJECTIVE -- The use of fasting plasma glucose (FPG) level 7.0 mmol/l leads to under-
diagnosis of type 2 diabetes compared with the oral glucose tolerance test (OGTT).The aims of this study were 1) to com-
pare the utility of HbA1c and FPG at dif-
ferent thresholds as screening tests for
diagnosing type 2 diabetes, as defined by
OGTT criteria; 2) to determine the rela-
tionship between HbA1c and FPG and
cardiovascular risk; and 3) to compare
HbA1c measured by HPLC with the result
obtained using a portable device
(DCA2000; Bayer Diagnostics, Mulgrave,
Australia) to assess the potential utility of
the latter in screening for type 2 diabetes. RESEARCH DESIGN AND
METHODS
Subjects
Subjects were recruited for this study by
community advertisement for people
with obesity, family history of diabetes,
history of gestational diabetes, or symp-
toms such as polyuria and polydipsia. All
individuals older than 18 years of age
without a previous diagnosis of type 2 di-
abetes were tested if they responded to the
advertisement with a request for screen-
ing. Pregnant women were excluded from
the study. Patients referred by general
practitioners and other hospital special-
ists for an OGTT were offered the oppor-
tunity to participate in the study. The Ethics Com-
mittee of the Royal Adelaide Hospital
approved the protocol. Informed consent
was obtained from all volunteers. Study design
Subjects fasted from food and fluid from
11:00 P.M. the previous night and at-
tended the Endocrine Test Unit at the
Royal Adelaide Hospital between 8:00
A.M. and 9:00 A.M. Subjects were asked to
complete a questionnaire to document
the presence of ischemic heart disease,
hypertension, and hyperlipidemia and
whether there was a family history of type
2 diabetes. Height, weight, and waist cir-
cumference were measured. A forearm
vein was then cannulated with a 19-g but-
terfly and 5 ml of venous blood was col-
lected for measurement of glucose and
HbA1c. Thereafter, 75 g of glucose was
administered orally and 5 ml of blood was
collected at 120 min for measurement of
plasma glucose. All patients and their
general practitioners were sent a letter in-
forming them of the results, and patients
were advised by telephone and by letter to
seek follow-up whenever either diabetes
or IGT was detected. Assays
Plasma glucose was measured by the hex-
okinase method, which has an interassay
CV of 1.9% at a glucose level of 4.8
mmol/l. HbA1c was measured by HPLC
using a spherical cation exchange gel,
which has an interassay CV of 2% at an
HbA1c level of 6%. HbA1c results from our
laboratory (Institute of Medical and Vet-
erinary Science) were referenced to the
National Glycohemoglobin Standardisa-
tion Program.Abbreviations: ADA, American Diabetes Association; CV, coefficient of variation; FPG, fasting plasma
glucose; HPLC, high-performance liquid chromatography; IFG, impaired fasting glycemia; IGT, impaired
glucose tolerance; OGTT, oral glucose tolerance test; ROC, receiver operating characteristic; WHO, World
Health Organization.Guerci B, Durain D, Leblanc H, Rouland
JC, Passa P, Godeau T, Charbonnel B,
Mathieu-Daude JC, Boniface H, Monnier
L, Dauchy F, Slama G, Drouin P: Multi-
centre evaluation of the DCA 2000 system
for measuring glycated haemoglobin:
DCA 2000 study group.Diabete Metab 23:
195-201, 1997
18.Macrovascular risk and diagnostic criteria for type 2 diabetes
488 DIABETES CARE, VOLUME 26, NUMBER 2, FEBRUARY 2003
used self-reported data to evaluate cardio-
vascular risk, our data relating to cardio-
vascular risk are consistent with the
results of other studies demonstrating an
association between cardiovascular dis-
ease and increasing FPG and HbA1c, even
in the nondiabetic range (18,20,29).McCance DR, Hanson RL, Charles MA,
Lennart THJ, Pettitt DJ, Bennett PH,
Knowler WC: Comparison of tests for gly-
cated haemoglobin and fasting and two
hour plasma glucose concentrations as di-
agnostic methods for diabetes.More-
over, data from the Diabetes Control and
Complications Trial (DCCT) (21) and
U.K. Prospective Diabetes Study (UK-
PDS) (22) demonstrate that there remains
a significant risk of microvascular disease
with HbA1c levels well below 8%, and
even at an HbA1c of 6%, there is a 75%
Figure 1--ROC curves comparing FPG (F), HbA1c by HPLC (OE), and HbA1c by DCA2000 ()
as diagnostic indicators for diabetes.In situations in which fasting blood
glucose can be readily obtained, a cutoff
of 6.4 mmol/l results in diagnosis of more
diabetic subjects than HbA1c as well as
identification of those at significant risk
for cardiovascular disease, in whom max-
imal intervention, whether pharmacolog-
ical or nonpharmacological, should be
targeted.Wahl PW, Savage PJ, Psaty BM, Orchard
TJ, Robbins JA, Tracey RP: Diabetes in
older adults: comparison of 1997 Ameri-
can Diabetes Association classification of
diabetes mellitus with 1985 WHO classi-
fication.Khaw KT, Wareham N, Luben R, Bing-
ham S, Oakes S, Welch A, Day N:
Glycated haemoglobin, diabetes, and
mortality in men in Norfolk cohort of Eu-
ropean Prospective Investigation of Can-
cer and Nutrition.Rohlfing CL, Little RR, Wiedmeyer HM,
England JD, Madsen R, Harris MI, Flegal
KM, Eberhardt MS, Goldstein DE: Use of
GHb (HbA1c) in screening for undiag-
nosed diabetes in the U.S. population.Perry RC, Shankar RR, Fineberg N, McGill
J, Baron AD: HbA1c measurement im-
proves the detection of type 2 diabetes in
high risk individuals with non-diagnostic
levels of fasting plasma glucose.The ADA
also created a new category termed im-
paired fasting glycemia (IFG) to describe
patients with FPG levels of 6.1-6.9
mmol/l (5) to categorize individuals at in-
creased risk for type 2 diabetes and those
who may be at increased cardiovascular
risk.Gabir MM, Hanson WC, Dabelea D, Im-
peratore G, Roumain J, Bennett PH,
Knowler WC: The 1997 American Diabe-
tes Association and 1999 WHO criteria
for hyperglycaemia in the diagnosis and
prediction of diabetes.The current OGTT and FPG thresh-
olds for diagnosis of diabetes are based on
their association with microvascular dis-
ease, the incidence of which increases
sharply above currently defined glycemic
thresholds.We hy-
pothesized that levels of HbA1c may in-
crease progressively with increasing
plasma glucose levels, even below con-
ventionally defined diabetic thresholds,
and are associated with the risk of macro-
vascular disease.Statistical analysis
Results are presented as means SD. The
receiver operating characteristic (ROC)
was used to describe the ability of HbA1c
(HPLC or DCA2000) and FPG to deter-
mine the presence or absence of type 2
diabetes as defined by the OGTT.Harris MI, Eastman RC, Cowie CC, Flegal
KM, Eberhardt MS: Comparison of diabe-
tes diagnostic categories in the U.S. pop-
ulation according to 1997 American
Diabetes association and 1980-85 World
Health Organization diagnostic criteria.Gabir MM, Hanson RL, Dabelea D, Im-
peratore G, Roumain J, Bennett PH,
Knowler WC: Plasma glucose and predic-
tion of microvascular disease and mortal-
ity.Franse LV, Di Bari M, Shorr RI, Resnick
HE, Van Eijk JTM, Bauer DC, Newman
AB, Pahor M: Type 2 diabetes in older
well-functioning people: who is undiag-
nosed?In contrast to other studies that have
evaluated the use of glucose and HbA1c as
screening tests, we studied smaller num-
bers of subjects prospectively rather than
derived data retrospectively but obtained
consistent results.The OGTT is a time-consuming,
poorly reproducible, inconvenient, and
expensive test that we would argue can
largely be avoided in favor of an HbA1c or
FPG, using lower diagnostic thresholds
and risk factor assessment to provide the
most rational approach to subsequent
management.The first subset should
be considered diabetic because they are at
increased risk for cardiovascular and mi-
crovascular complications; these subjects
should receive standard diabetic assess-
ment (e.g., for retinopathy, neuropathy,
and nephropathy) as well as for cardio-
vascular disease.The aim of this study was to evaluate the use of HbA1c and FPG as predictors of type 2
diabetes and cardiovascular risk and, accordingly, to develop a rational approach to screening for
abnormalities of glucose tolerance.Problems with the use of
HbA1c for screening have included vari-
ability and poor standardization of assays,
biological variability of HbA1c levels,
overlap between subjects with and with-
out diabetes as compared with fasting or
2-h glucose levels (5,14-17), and poor
sensitivity (12).Based on an ROC analysis, the areas
under the curve (predictive values) of
HbA1c as measured by HPLC and
DCA2000 for detecting type 2 diabetes,
compared with OGTT, were 0.893 and
0.911, respectively (2 0.53, df 2,
P 0.77) (Fig.CONCLUSIONS -- These results
show that FPG and HbA1c (by either
method) will diagnose or exclude diabe-
tes with certainty in only a minority
(15%) of subjects when the OGTT, with
currently defined cutoffs, is used as the
gold standard.Wiener K, Roberts NB: The relative merits
of haemoglobin A1c and fasting plasma
glucose as first line diagnostic tests for di-
abetes mellitus in non-pregnant subjects.The World Health Organization
(WHO) and subsequently the Australian
Diabetes Society similarly adopted an
FPG level of 7 mmol/l as the threshold for
diagnosing type 2 diabetes (6,7); how-
ever, these organizations continue to rec-
ommend use of the OGTT, because
patients with type 2 diabetes based on an
OGTT often have a nondiabetic FPG level
(1,8,9).Log-binomial regression was used to
determine the risk ratios (and 95% CIs)
for the presence of ischemic heart disease
for each SD increase in HbA1c, as mea-
sured by either HPLC or using the
DCA2000 method and the FPG.The regression data for HbA1c by
DCA2000 versus HPLC reveals a small in-
Macrovascular risk and diagnostic criteria for type 2 diabetes
486 DIABETES CARE, VOLUME 26, NUMBER 2, FEBRUARY 2003
tercept of 0.2 but no change in slope.Neither HbA1c (HPLC or DCA2000) nor
FPG remained independent risk factors
for cardiovascular disease after adjust-
ment for age, waist circumference, hyper-
tension, and high cholesterol.Table 1--The sensitivity, specificity, and cardiovascular risk ratio at each cutoff of HbA1c (by HPLC), HbA1c (by DCA2000), and FPG
HbA1c by HPLC HbA1c by DCA2000 FPG (mmol/l)
HbA1c (%) Sen (%) Spec (%) CV HbA1c (%) Sen (%) Spec (%) CV FPG Sen (%) Spec (%) CV
3.9 100 0.22 1 4.0 100 0.2 1 3.0 100 0 1.0
4.7 100 10.0 1.3 5.0 100 11.1 1.3 4.7 100 23.1 1.4
5.6 85.2 80.5 1.8 5.8 85.2 77.8 1.6 5.6 79.6 85.8 1.7
6.2 42.6 99.1 2.3 6.8 42.6 99.6 2.1 6.4 59.3 99.1 2.0
6.8 22.2 100 2.8 7.3 20.4 100 2.4 7.7 31.5 100 2.5
Sen, sensitivity; Spec, specificity.Peters AL, Davidson MB, Schringer DL,
Hasselblad V: A clinical approach for the
diagnosis of diabetes mellitus: an analysis
using glycosylated haemoglobin levels.Colman PG, Goodall GI, Garcia-Webb P,
Williams PF, Dunlop ME: Glycohaemo-
globin: a crucial measurement in modern
diabetes measurement.The Diabetes Control and Complications
Trial Research Group: The effect of inten-
sive treatment of diabetes on the develop-
ment and progression of long term
complications of insulin-dependant dia-
betes mellitus.N Engl J Med 329:977-986,
1993
23.Measurement of HbA1c
is used to determine average glycemic
control over an 8- to 12-week period, and
HbA1c level has been linked to develop-
ment of microvascular complications
such as neuropathy, nephropathy, and
retinopathy (7).Pathophysiology/Complications
ORIGINAL ARTICLE
DIABETES CARE, VOLUME 26, NUMBER 2, FEBRUARY 2003 485
the-spot results comparable to those
obtained with HPLC can be obtained us-
ing automated and portable devices (17).HbA1c was also measured
using the DCA2000 (Bayer Diagnostics),
a portable device that uses an immunoas-
say technique with a monoclonal anti-
body directed against a sequence of the
HbA1c molecule (19).When measured by DCA2000, HbA1c
6.2% (sensitivity 72.2%, specificity
94.7%) was the best predictor of diabetes,
and HbA1c levels 5.0 and 6.8% pre-
dict the absence or presence of diabetes,
respectively, with almost 100% certainty
(Table 1).Kilpatrick ES, Maylor PW, Keevil BG: Bi-
ological variation of glycated haemoglo-
bin.The corresponding
cutoffs were 5.0 and 6.8% for HbA1c (DCA2000 HPLC device; Bayer Diagnostics, Mulgrave,
Australia) and 4.7 and 6.4 mmol/l for FPG.The American Diabetes Asso-
ciation (ADA) based diagnosis of diabetes
on a fasting plasma glucose (FPG) level of
7.0 mmol/l because this level correlates
with a 2-h (post-75 g glucose) level of
11.1 mmol/l (5).Given
that a major part of the morbidity and
mortality from type 2 diabetes arises from
macrovascular disease such as ischemic
heart disease and not just microvascular
disease, any screening test for diabetes
would be more meaningful if it could also
predict cardiovascular disease.The repro-
ducibility of measurements of FPG, 2-h
glucose, and HbA1c by each method was
calculated for the 41 subjects, who were
tested twice, and the intrasubject CV was
determined (15).Accordingly, we propose that
there is a rational basis for using either
FPG or HbA1c for purposes of screening
and assigning risk and, therefore, target-
ing the most appropriate group of indi-
viduals for further investigation and
intervention.As with FPG, the risk of microvascular
disease is low with an HbA1c 6.1%, but
a relatively high risk of macrovascular
disease remains and accordingly aggres-
sive risk factor reduction is warranted.There is a relationship between HbA1c
and FPG and the risk of both microvascu-
lar (4) and macrovascular disease (1,20),
although the increased risk of macrovas-
cular disease occurs at lower glycemic
thresholds.Davidson MB, Schriger DL, Peters AL,
Lorber B: Relationship between fasting
plasma glucose and glycosylated haemo-
globin.RESEARCH DESIGN AND METHODS -- OGTT and measurement of HbA1c and FPG
levels were performed in 505 subjects screened for type 2 diabetes.When measured using
high-performance liquid chromatogra-
phy (HPLC), however, the test has high
precision (interassay coefficient of varia-
tion [CV] 1-2%).Sensitivity is the
fraction of individuals at or above the
HbA1c cutoff point who have diabetes,
whereas specificity is the fraction of indi-
viduals with an HbA1c level below the cut-
off point who do not have diabetes.Reproducibility
There was a within-subject CV of 2.2% for
HbA1c by HPLC, 2.7% for HbA1c by
DCA2000, 4.9% for FPG, and 16.0% for
120-min plasma glucose after a 75-g oral
glucose load.The detection of type 2 di-
abetes has been reported by others to
halve when ADA as opposed to WHO cri-
teria are applied (1).Wahl et al. (1)
showed that at an FPG level of 6.38
mmol/l, the prevalence of diabetes by
ADA and 1985 WHO criteria were simi-
lar.References
1. 1).2).
Implications for the use of FPG and HbA1c for cost-effective screening
DAVID R. JESUDASON, MBBS, FRACP1
KERRIE DUNSTAN, RN1 DARRYL LEONG, MBBS1
GARY A. WITTERT, MBBCH, MD, FRACP1,2
OBJECTIVE — The use of fasting plasma glucose (FPG) level 7.0 mmol/l leads to under-
diagnosis of type 2 diabetes compared with the oral glucose tolerance test (OGTT). The OGTT
is of limited use for population screening. Most of the increase in cardiovascular risk in relation
to increasing blood glucose occurs before the threshold at which the diagnosis of type 2 diabetes
is made. The aim of this study was to evaluate the use of HbA1c and FPG as predictors of type 2
diabetes and cardiovascular risk and, accordingly, to develop a rational approach to screening for
abnormalities of glucose tolerance.
RESEARCH DESIGN AND METHODS — OGTT and measurement of HbA1c and FPG
levels were performed in 505 subjects screened for type 2 diabetes. Anthropomorphic measure-
ments were obtained. A cardiovascular risk factor questionnaire was completed.
RESULTS — The subjects were aged 19–88 years (mean 53.8). The incidence of type 2
diabetes was 10.4% based on the OGTT and 4% based on an FPG level 7.0 mmol/l. Using
high-performance liquid chromatography (HPLC), HbA1c of 4.7 and 6.2% predicted with
certainty the absence or presence of type 2 diabetes as defined by the OGTT. The corresponding
cutoffs were 5.0 and 6.8% for HbA1c (DCA2000 HPLC device; Bayer Diagnostics, Mulgrave,
Australia) and 4.7 and 6.4 mmol/l for FPG. However, 75–85% of subjects in each case had
intermediate values, which were therefore nondiagnostic. Cardiovascular risk increased at least
2.2 times at an HbA1c level 6.2% (by HPLC), 1.8–2.2 times at an HbA1c level of 5.6–6.1% (by
HPLC), 2 times at an FPG level 6.4 mmol/l, and 1.7–1.9 times at an FPG level of 5.6–6.3
mmol/l.
CONCLUSIONS — Measurement of FPG and HbA1c levels will diagnose or exclude type 2
diabetes with certainty in a minority (15%) of people. There is a continuous relationship between
FPG and HbA1c and cardiovascular risk. Accordingly, we propose that there is a rational basis for
using either FPG and HbA1c for purposes of screening and assigning risk. Individuals with an
HbA1c level of 5.6–6.1% and an FPG level of 5.6–6.3 mmol/l are at greatest risk for cardiovas-
cular disease and should be targeted for further evaluation. An algorithm outlining a cost-
effective approach is presented.
Diabetes Care 26:485–490, 2003
T
he incidence of type 2 diabetes var-
ies from 3.6 to 14.8%, depending on
the population being screened (1,2)
and the diagnostic criteria used. Up to
50% of diabetic subjects remain undetec-
ted. The oral glucose tolerance test
(OGTT) is the gold standard for diagnos-
ing type 2 diabetes. It has limited use for
mass screening, due to the need for fast-
ing, the time-consuming nature of the
test, and poor reproducibility of the re-
sults (3,4). The American Diabetes Asso-
ciation (ADA) based diagnosis of diabetes
on a fasting plasma glucose (FPG) level of
7.0 mmol/l because this level correlates
with a 2-h (post–75 g glucose) level of
11.1 mmol/l (5). It was hoped the better
reproducibility of FPG and its relative
convenience would increase the number
of diabetic subjects diagnosed. The ADA
also created a new category termed im-
paired fasting glycemia (IFG) to describe
patients with FPG levels of 6.1–6.9
mmol/l (5) to categorize individuals at in-
creased risk for type 2 diabetes and those
who may be at increased cardiovascular
risk. The World Health Organization
(WHO) and subsequently the Australian
Diabetes Society similarly adopted an
FPG level of 7 mmol/l as the threshold for
diagnosing type 2 diabetes (6,7); how-
ever, these organizations continue to rec-
ommend use of the OGTT, because
patients with type 2 diabetes based on an
OGTT often have a nondiabetic FPG level
(1,8,9).
To improve the detection rate of type
2 diabetes, alternative approaches to
screening have been proposed, such as a
lower threshold for FPG (8) or the use of
HbA1c (4,10–12). Measurement of HbA1c
is used to determine average glycemic
control over an 8- to 12-week period, and
HbA1c level has been linked to develop-
ment of microvascular complications
such as neuropathy, nephropathy, and
retinopathy (7). Compared with the
OGTT, HbA1c measurement is quicker, is
more convenient, and avoids the need for
fasting (3). Problems with the use of
HbA1c for screening have included vari-
ability and poor standardization of assays,
biological variability of HbA1c levels,
overlap between subjects with and with-
out diabetes as compared with fasting or
2-h glucose levels (5,14–17), and poor
sensitivity (12). When measured using
high-performance liquid chromatogra-
phy (HPLC), however, the test has high
precision (interassay coefficient of varia-
tion [CV] 1–2%). Furthermore, rapid, on-
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
From the 1
Department of Endocrinology and Metabolism, Royal Adelaide Hospital, Adelaide, Australia; and
the 2
Department of Medicine, University of Adelaide, Adelaide, Australia.
Address correspondence and reprint requests to Associate Professor Gary Wittert, University of Adelaide
Department of Medicine, Royal Adelaide Hospital, North Terrace, Adelaide SA 5000, Australia. E-mail:
[email protected].
Received for publication 3 April 2002 and accepted in revised form 24 October 2002.
Abbreviations: ADA, American Diabetes Association; CV, coefficient of variation; FPG, fasting plasma
glucose; HPLC, high-performance liquid chromatography; IFG, impaired fasting glycemia; IGT, impaired
glucose tolerance; OGTT, oral glucose tolerance test; ROC, receiver operating characteristic; WHO, World
Health Organization.
A table elsewhere in this issue shows conventional and Syste`me International (SI) units and conversion
factors for many substances.
Pathophysiology/Complications
ORIGINAL ARTICLE
DIABETES CARE, VOLUME 26, NUMBER 2, FEBRUARY 2003 485
the-spot results comparable to those
obtained with HPLC can be obtained us-
ing automated and portable devices (17).
The current OGTT and FPG thresh-
olds for diagnosis of diabetes are based on
their association with microvascular dis-
ease, the incidence of which increases
sharply above currently defined glycemic
thresholds. Macrovascular disease, how-
ever, seems to increase gradually in pre-
diabetic states such as impaired glucose
tolerance (IGT) and IFG (4,18). Given
that a major part of the morbidity and
mortality from type 2 diabetes arises from
macrovascular disease such as ischemic
heart disease and not just microvascular
disease, any screening test for diabetes
would be more meaningful if it could also
predict cardiovascular disease. We hy-
pothesized that levels of HbA1c may in-
crease progressively with increasing
plasma glucose levels, even below con-
ventionally defined diabetic thresholds,
and are associated with the risk of macro-
vascular disease.
The aims of this study were 1) to com-
pare the utility of HbA1c and FPG at dif-
ferent thresholds as screening tests for
diagnosing type 2 diabetes, as defined by
OGTT criteria; 2) to determine the rela-
tionship between HbA1c and FPG and
cardiovascular risk; and 3) to compare
HbA1c measured by HPLC with the result
obtained using a portable device
(DCA2000; Bayer Diagnostics, Mulgrave,
Australia) to assess the potential utility of
the latter in screening for type 2 diabetes.
RESEARCH DESIGN AND
METHODS
Subjects
Subjects were recruited for this study by
community advertisement for people
with obesity, family history of diabetes,
history of gestational diabetes, or symp-
toms such as polyuria and polydipsia. All
individuals older than 18 years of age
without a previous diagnosis of type 2 di-
abetes were tested if they responded to the
advertisement with a request for screen-
ing. Pregnant women were excluded from
the study. Patients referred by general
practitioners and other hospital special-
ists for an OGTT were offered the oppor-
tunity to participate in the study. To
determine reproducibility of the tests
used, 41 subjects were tested on two oc-
casions (1 week apart). The Ethics Com-
mittee of the Royal Adelaide Hospital
approved the protocol. Informed consent
was obtained from all volunteers.
Study design
Subjects fasted from food and fluid from
11:00 P.M. the previous night and at-
tended the Endocrine Test Unit at the
Royal Adelaide Hospital between 8:00
A.M. and 9:00 A.M. Subjects were asked to
complete a questionnaire to document
the presence of ischemic heart disease,
hypertension, and hyperlipidemia and
whether there was a family history of type
2 diabetes. Height, weight, and waist cir-
cumference were measured. A forearm
vein was then cannulated with a 19-g but-
terfly and 5 ml of venous blood was col-
lected for measurement of glucose and
HbA1c. Thereafter, 75 g of glucose was
administered orally and 5 ml of blood was
collected at 120 min for measurement of
plasma glucose. All patients and their
general practitioners were sent a letter in-
forming them of the results, and patients
were advised by telephone and by letter to
seek follow-up whenever either diabetes
or IGT was detected.
Assays
Plasma glucose was measured by the hex-
okinase method, which has an interassay
CV of 1.9% at a glucose level of 4.8
mmol/l. HbA1c was measured by HPLC
using a spherical cation exchange gel,
which has an interassay CV of 2% at an
HbA1c level of 6%. HbA1c results from our
laboratory (Institute of Medical and Vet-
erinary Science) were referenced to the
National Glycohemoglobin Standardisa-
tion Program. HbA1c was also measured
using the DCA2000 (Bayer Diagnostics),
a portable device that uses an immunoas-
say technique with a monoclonal anti-
body directed against a sequence of the
HbA1c molecule (19). A result is available
within 6 min of testing, with a CV of
2.2%.
Statistical analysis
Results are presented as means SD. The
receiver operating characteristic (ROC)
was used to describe the ability of HbA1c
(HPLC or DCA2000) and FPG to deter-
mine the presence or absence of type 2
diabetes as defined by the OGTT. The
ROC describes the diagnostic properties
of a test by plotting sensitivity as a func-
tion of 1-specificity (20). Sensitivity is the
fraction of individuals at or above the
HbA1c cutoff point who have diabetes,
whereas specificity is the fraction of indi-
viduals with an HbA1c level below the cut-
off point who do not have diabetes. The
area under the ROC curve represents the
probability that a subject chosen at ran-
dom from the group with the outcome of
interest (type 2 diabetes) had a higher
value than a subject without. Wald 2
analysis was used to compare the respec-
tive areas under the curve for the different
diabetic screening tests. The relationship
between HbA1c as measured by HPLC
and using the DCA2000 was determined
using linear regression.
Log-binomial regression was used to
determine the risk ratios (and 95% CIs)
for the presence of ischemic heart disease
for each SD increase in HbA1c, as mea-
sured by either HPLC or using the
DCA2000 method and the FPG. A risk of
1 was arbitrarily assigned to a cutoff 2 SD
below the mean for each of the aforemen-
tioned measurements, and risk ratios
were then determined for higher levels.
The risk ratio was also calculated for each
parameter after adjusting for the presence
of the other stated risk factors. The repro-
ducibility of measurements of FPG, 2-h
glucose, and HbA1c by each method was
calculated for the 41 subjects, who were
tested twice, and the intrasubject CV was
determined (15).
RESULTS — A total of 505 subjects
aged 19–88 years (mean age 53.8 years)
were studied. There were 294 (58.2%)
women and 211 (41.8%) men. Using the
Australian Diabetes Society and WHO
criteria, the incidence of type 2 diabetes
was 10.7% (54 subjects) and the inci-
dence of IGT was 24.4% (123 subjects).
Using the ADA criteria, the incidence of
type 2 diabetes was 4.0% (20 subjects)
and the incidence of IFG was 7.1% (36
subjects).
Subjects were divided according to
the presence or absence of diabetes ac-
cording to OGTT criteria. Nondiabetic
subjects had a mean HbA1c (HPLC) of
5.2% (range 3.5– 6.6), a mean HbA1c
(DCA2000) of 5.5% (4–6.9), and a mean
FPG of 5.1 mmol/l (3–6.7). Diabetic sub-
jects had a mean HbA1c (HPLC) of 6.5%
(4.7–12.2), a mean HbA1c (DCA2000) of
7.0% (5–13.1), and a mean FPG of 7.4
mmol/l (4.7–15.7). There was a good cor-
relation between the HbA1c values ob-
tained by HPLC and DCA2000 (R2
0.876). The regression data for HbA1c by
DCA2000 versus HPLC reveals a small in-
Macrovascular risk and diagnostic criteria for type 2 diabetes
486 DIABETES CARE, VOLUME 26, NUMBER 2, FEBRUARY 2003
tercept of 0.2 but no change in slope.
Accordingly, there is a constant bias of
0.2 but no evidence of relative bias.
Based on our ROC curves, our cutoff cri-
teria showed higher values for DCA2000
than HPLC.
Based on an ROC analysis, the areas
under the curve (predictive values) of
HbA1c as measured by HPLC and
DCA2000 for detecting type 2 diabetes,
compared with OGTT, were 0.893 and
0.911, respectively (2 0.53, df 2,
P 0.77) (Fig. 1).
When measured by HPLC, HbA1c
5.7% predicted type 2 diabetes with a
sensitivity of 80.0% and a specificity of
86.3%. HbA1c levels 4.7 and 6.2%
have almost 100% accuracy for predicting
the absence and presence of type 2 diabe-
tes, respectively (Table 1).
When measured by DCA2000, HbA1c
6.2% (sensitivity 72.2%, specificity
94.7%) was the best predictor of diabetes,
and HbA1c levels 5.0 and 6.8% pre-
dict the absence or presence of diabetes,
respectively, with almost 100% certainty
(Table 1). Using FPG, the area under the
ROC curve was 0.9065. FPG 6.0
mmol/l (sensitivity 74.1%, specificity
94.5%) was the best predictor of type 2
diabetes as defined by OGTT. FPG levels
4.7 and 6.4 mmol/l had almost 100%
accuracy for detecting the absence or
presence of type 2 diabetes.
Cardiovascular risk
The mean SD for HbA1c by HPLC,
HbA1c by DCA2000, and FPG were 5.3
0.74%, 5.6 0.84%, and 5.3 1.2
mmol/l, respectively. The risk ratio (95%
CI) for each SD change in HbA1c by
HPLC, HbA1c by DCA2000, and FPG
were 1.3 (1.1–1.5; P 0.0002), 1.24
(1.1–1.4; P 0.0038), and 1.26 (1.1–
1.4; P 0.0001), respectively. The rela-
tive cardiovascular risks associated with
different cutoffs of HbA1c (HPLC and
DCA2000) and FPG are shown in Table 1.
Neither HbA1c (HPLC or DCA2000) nor
FPG remained independent risk factors
for cardiovascular disease after adjust-
ment for age, waist circumference, hyper-
tension, and high cholesterol. After
adjustment for these risk factors, the rel-
ative risk of ischemic heart disease for
HbA1c by HPLC, HbA1c by DCA2000, or
FPG was 1.1 (0.9–1.4; P 0.22), 1.1
(0.8–1.4; P 0.64), and 1.2 (0.99–1.4;
P 0.059). Only age and high cholesterol
were independent risk factors for cardio-
vascular disease. For example, when ana-
lyzed with HbA1c (HPLC) the relative risk
of ischemic heart disease for age was 2.0
(1.4–2.9; P 0.0002) and for high cho-
lesterol was 2.2 (1.2–3.9; P 0.01). The
ischemic heart disease risk for waist cir-
cumference was 1.2 (0.9–1.6; P 0.18)
and for hypertension was 1.7 (0.8–3.3;
P 0.14).
Reproducibility
There was a within-subject CV of 2.2% for
HbA1c by HPLC, 2.7% for HbA1c by
DCA2000, 4.9% for FPG, and 16.0% for
120-min plasma glucose after a 75-g oral
glucose load.
CONCLUSIONS — These results
show that FPG and HbA1c (by either
method) will diagnose or exclude diabe-
tes with certainty in only a minority
(15%) of subjects when the OGTT, with
currently defined cutoffs, is used as the
gold standard. Although FPG and HbA1c
do not seem to be independent measures
of cardiovascular risk, there is a continu-
ous relationship between both of these
measures and cardiovascular risk. More-
over, data from the Diabetes Control and
Complications Trial (DCCT) (21) and
U.K. Prospective Diabetes Study (UK-
PDS) (22) demonstrate that there remains
a significant risk of microvascular disease
with HbA1c levels well below 8%, and
even at an HbA1c of 6%, there is a 75%
Figure 1—ROC curves comparing FPG (F), HbA1c by HPLC (Œ), and HbA1c by DCA2000 ()
as diagnostic indicators for diabetes.
Table 1—The sensitivity, specificity, and cardiovascular risk ratio at each cutoff of HbA1c (by HPLC), HbA1c (by DCA2000), and FPG
HbA1c by HPLC HbA1c by DCA2000 FPG (mmol/l)
HbA1c (%) Sen (%) Spec (%) CV HbA1c (%) Sen (%) Spec (%) CV FPG Sen (%) Spec (%) CV
3.9 100 0.22 1 4.0 100 0.2 1 3.0 100 0 1.0
4.7 100 10.0 1.3 5.0 100 11.1 1.3 4.7 100 23.1 1.4
5.6 85.2 80.5 1.8 5.8 85.2 77.8 1.6 5.6 79.6 85.8 1.7
6.2 42.6 99.1 2.3 6.8 42.6 99.6 2.1 6.4 59.3 99.1 2.0
6.8 22.2 100 2.8 7.3 20.4 100 2.4 7.7 31.5 100 2.5
Sen, sensitivity; Spec, specificity.
Jesudason and Associates
DIABETES CARE, VOLUME 26, NUMBER 2, FEBRUARY 2003 487
increased risk of microvascular complica-
tions of type 2 diabetes. Gabir et al. (23)
have shown that retinopathy and ne-
phropathy increase at an FPG level of 6.0
mmol/l. Accordingly, we propose that
there is a rational basis for using either
FPG or HbA1c for purposes of screening
and assigning risk and, therefore, target-
ing the most appropriate group of indi-
viduals for further investigation and
intervention.
If an FPG level 7 mmol/l is used, the
incidence of type 2 diabetes is underesti-
mated, as compared with the OGTT
(1,8,9,24). Only 4.0% of our subjects
were diabetic using FPG based on the
ADA criteria, compared with 10.4% using
WHO criteria. The detection of type 2 di-
abetes has been reported by others to
halve when ADA as opposed to WHO cri-
teria are applied (1). Wahl et al. (1)
showed that at an FPG level of 6.38
mmol/l, the prevalence of diabetes by
ADA and 1985 WHO criteria were simi-
lar. In the DECODE study, the FPG level
that predicted a 2-h value of 11.1 mmol/l
was 6.4 mmol/l in men (25). Taken to-
gether, the data suggest that an FPG level
6.4 mmol/l is the most appropriate level
at which to diagnose type 2 diabetes and
only 40% (rather than 60%) of individ-
uals with type 2 diabetes would be
missed. Our study has also shown that
when the FPG level is 4.7 mmol/l, type
2 diabetes can be confidently excluded;
73% of all subjects had an FPG level
between 4.7 and 6.3 mmol/l, and 17%
of these individuals had an FPG level of
5.6 – 6.3 mmol/l. Of this latter group,
13.6% (12 of 88) were diabetic based on
an OGTT.
The relative cardiovascular risk was at
least 2 in the group with FPG 6.3
mmol/l and was 1.7–1.9 in those with an
FPG of 5.6–6.3 mmol/l. Therefore, al-
though an FPG of 5.6–6.3 mmol/l is as-
sociated with a low risk of microvascular
disease, there is a relatively high risk of
macrovascular disease. Aggressive treat-
ment of cardiovascular risk factors and at-
tention to lifestyle issues such as diet and
exercise are indicated. Moreover, we
would argue that lifestyle interventions to
prevent progression to type 2 diabetes
would be most appropriately targeted to
this group (26).
Our data also show that type 2 diabe-
tes is present at an HbA1c (HPLC) 6.2%,
and the detection rate is better than when
the ADA criteria are used. If an OGTT was
performed, however, 57% more of the in-
dividuals would have been diagnosed as
having type 2 diabetes. An HbA1c (HPLC)
4.7% excludes type 2 diabetes. How-
ever, 86% of all subjects had an HbA1c
between 4.7 and 6.1%; 21% of these sub-
jects had an HbA1c of 5.6–6.1%. Of the
latter subjects, 21.5% (23 of 107) were
diabetic on the OGTT.
We did not observe an independent
relationship between HbA1c and cardio-
vascular risk, although such an associa-
tion has previously been reported in a
larger study (20). The relative cardiovas-
cular risk in our group with an HbA1c
(HPLC) 6.1% was at least 2.3, and in
those with an HbA1c of 5.6–6.1%, the
relative cardiovascular risk was 1.8–2.2.
As with FPG, the risk of microvascular
disease is low with an HbA1c 6.1%, but
a relatively high risk of macrovascular
disease remains and accordingly aggres-
sive risk factor reduction is warranted.
The situation with HbA1c as measured us-
ing DCA2000 is analogous, although
the cutoffs were higher. Type 2 diabetes
is diagnosed at HbA1c 6.8%, whereas
HbA1c 5.0% excludes diabetes confi-
dently. The high cardiovascular risk
group were those subjects with an HbA1c
of 5.8–6.7%.
Wiener et al. (12) found that HbA1c
6.2% had 100% specificity for diagnos-
ing type 2 diabetes. They argued that
HbA1c should be used in screening to re-
duce the number of OGTTs performed
but that the OGTT should continue to be
used to avoid missing subjects with type 2
diabetes. Interestingly, they acknowl-
edged that if there were a relationship be-
tween HbA1c and complications of type 2
diabetes, then it could replace the OGTT.
Davidson et al. (27) suggested measuring
HbA1c to determine whether diabetes was
present in subjects with borderline FPG
(6.1–7.7 mmol/l) to avoid inappropriate
diagnosis of type 2 diabetes. In the study
by Perry et al. (28), an HbA1c 6.1% was
considered specific for type 2 diabetes
and was used to confirm the presence or
absence of the disease in subjects with an
FPG level between 5.5 and 8 mmol/l.
We have shown that a reduction in
the FPG level at which type 2 diabetes is
diagnosed will lead to a comparable in-
crease in the detection rate of diabetes. If
we combined FPG and HbA1c, we de-
tected an additional two subjects with di-
abetes (4%). We would argue, however,
that intervention is more logically based
on the risk of complications or associated
diseases rather than a comparison with
arbitrary cutoffs on the OGTT. In a large
meta-analysis, HbA1c was proposed as a
means to identify diabetic subjects requir-
ing pharmacological intervention (3).
There is a relationship between HbA1c
and FPG and the risk of both microvascu-
lar (4) and macrovascular disease (1,20),
although the increased risk of macrovas-
cular disease occurs at lower glycemic
thresholds.
In contrast to other studies that have
evaluated the use of glucose and HbA1c as
screening tests, we studied smaller num-
bers of subjects prospectively rather than
derived data retrospectively but obtained
consistent results. Moreover, although we
Figure 2—An algorithm for diagnosing type 2 diabetes and assigning cardiovascular risk using FPG or HbA1c by HPLC.
Macrovascular risk and diagnostic criteria for type 2 diabetes
488 DIABETES CARE, VOLUME 26, NUMBER 2, FEBRUARY 2003
used self-reported data to evaluate cardio-
vascular risk, our data relating to cardio-
vascular risk are consistent with the
results of other studies demonstrating an
association between cardiovascular dis-
ease and increasing FPG and HbA1c, even
in the nondiabetic range (18,20,29).
The OGTT is a time-consuming,
poorly reproducible, inconvenient, and
expensive test that we would argue can
largely be avoided in favor of an HbA1c or
FPG, using lower diagnostic thresholds
and risk factor assessment to provide the
most rational approach to subsequent
management. We have proposed an algo-
rithm for how this may occur (Fig. 2).
Using this algorithm, whether with HbA1c
or with FPG, the population is divided
into four subsets. The first subset should
be considered diabetic because they are at
increased risk for cardiovascular and mi-
crovascular complications; these subjects
should receive standard diabetic assess-
ment (e.g., for retinopathy, neuropathy,
and nephropathy) as well as for cardio-
vascular disease. The second subset is at
high cardiovascular risk and at greatest
risk for future progression to diabetes.
Clinicians should target the cardiovascu-
lar risk factors of these subjects and screen
for diabetes with HbA1c or FPG every
12–24 months, depending on previous
results. The third subset has a cardiovas-
cular risk above baseline although lower
than the first two subsets. In the absence
of any other indications, these subjects do
not require any specific intervention but
could receive general dietary and lifestyle
advice as well as appropriate follow-up.
The fourth subset is at lowest risk and can
be reassured, although it is always appro-
priate to encourage healthy behaviors.
The algorithm in Fig. 2 illustrates this ap-
proach using FPG and HbA1c (HPLC).
Portable devices for measuring HbA1c
are suitable for transport to community
settings and, accordingly, provide the po-
tential for mass screening. Fasting is not
required and there is no need for further
HbA1c measurement in those subse-
quently determined to have type 2 diabe-
tes. In situations in which fasting blood
glucose can be readily obtained, a cutoff
of 6.4 mmol/l results in diagnosis of more
diabetic subjects than HbA1c as well as
identification of those at significant risk
for cardiovascular disease, in whom max-
imal intervention, whether pharmacolog-
ical or nonpharmacological, should be
targeted.
Acknowledgments— This research was sup-
ported by the Royal Adelaide Hospital, the In-
stitute of Medical and Veterinary Science, and
a grant from Bayer Diagnostics.
References
older adults: comparison of 1997 Ameri-
can Diabetes Association classification of
diabetes mellitus with 1985 WHO classi-
fication. Lancet 352:1012–1015, 1998
1000–1001, 1998
3. Peters AL, Davidson MB, Schringer DL,
Hasselblad V: A clinical approach for the
diagnosis of diabetes mellitus: an analysis
using glycosylated haemoglobin levels.
JAMA 276:1246–1252, 1996
4. McCance DR, Hanson RL, Charles MA,
Lennart THJ, Pettitt DJ, Bennett PH,
Knowler WC: Comparison of tests for gly-
cated haemoglobin and fasting and two
hour plasma glucose concentrations as di-
agnostic methods for diabetes. BMJ 308:
1323–1328, 1994
5. American Diabetes Association: Report of
the Expert Committee on the Diagnosis
and Classification of Diabetes Mellitus.
Diabetes Care 20:1183–1197, 1997
Aust 170:375–379, 1999
7. Alberti KGMM, Zimmet PZ: Definition,
diagnosis and classification of diabetes
mellitus and its complications. Part 1.
Diagnosis and classification of diabetes
mellitus: provisional report of a WHO
consultation. Diabet Med 15:539–553,
1998
Knowler WC: The 1997 American Diabe-
tes Association and 1999 WHO criteria
for hyperglycaemia in the diagnosis and
prediction of diabetes. Diabetes Care 23:
1108–1112, 2000
9. Harris MI, Eastman RC, Cowie CC, Flegal
KM, Eberhardt MS: Comparison of diabe-
tes diagnostic categories in the U.S. pop-
ulation according to 1997 American
Diabetes association and 1980–85 World
Health Organization diagnostic criteria.
Diabetes Care 20:1859–1862, 1997
10. Rohlfing CL, Little RR, Wiedmeyer HM,
England JD, Madsen R, Harris MI, Flegal
KM, Eberhardt MS, Goldstein DE: Use of
GHb (HbA1c) in screening for undiag-
nosed diabetes in the U.S. population. Di-
abetes Care 23:187–191, 2000
for undiagnosed diabetes in the U.S. pop-
ulation (Letter). Diabetes Care 23:1207,
2000
12. Wiener K, Roberts NB: The relative merits
of haemoglobin A1c and fasting plasma
glucose as first line diagnostic tests for di-
abetes mellitus in non-pregnant subjects.
Diabet Med 15:558–563, 1998
Kilpatrick ES, Maylor PW, Keevil BG: Bi-
ological variation of glycated haemoglo-
bin. Diabetes Care 21:261–264, 1998
Colman PG, Goodall GI, Garcia-Webb P,
Williams PF, Dunlop ME: Glycohaemo-
globin: a crucial measurement in modern
diabetes measurement. Med J Aust 167:
96–98, 1997
Quality Control Surveys. Diabetes Care
21:265–270, 1998
17. Guerci B, Durain D, Leblanc H, Rouland
JC, Passa P, Godeau T, Charbonnel B,
Mathieu-Daude JC, Boniface H, Monnier
L, Dauchy F, Slama G, Drouin P: Multi-
centre evaluation of the DCA 2000 system
for measuring glycated haemoglobin:
DCA 2000 study group.Diabete Metab 23:
195–201, 1997
diabetes. Curr Opin Endocrinol Diabetes
7:197–202, 2000
HbA1c immunoassay analyser. Ann Clin
Biochem 31:367–370, 1994
Glycated haemoglobin, diabetes, and
mortality in men in Norfolk cohort of Eu-
ropean Prospective Investigation of Can-
cer and Nutrition. BMJ 322:1–6, 2001
Intensive blood glucose control with sul-
phonylureas or insulin compared with
conventional treatment and risk of com-
plications in-patients with type 2 diabetes
(UKPDS 33). Lancet 352:837–852, 1998
22. The Diabetes Control and Complications
Trial Research Group: The effect of inten-
sive treatment of diabetes on the develop-
ment and progression of long term
complications of insulin-dependant dia-
betes mellitus.N Engl J Med 329:977–986,
1993
Knowler WC: Plasma glucose and predic-
tion of microvascular disease and mortal-
ity. Diabetes Care 23:1113–1118, 2000
well-functioning people: who is undiag-
nosed? Diabetes Care 24:2065–2070,
2001
Jesudason and Associates
DIABETES CARE, VOLUME 26, NUMBER 2, FEBRUARY 2003 489
Is fasting glucose sufficient to define dia-
betes? Epidemiological data from 20 Eu-
ropean studies. Diabetologia 42:647–654,
1999
26. Diabetes Prevention Program Research
Group: Reduction in the incidence of type
2 diabetes with lifestyle intervention or
metformin. N Engl J Med 346:393–403,
2002
27. Davidson MB, Schriger DL, Peters AL,
Lorber B: Relationship between fasting
plasma glucose and glycosylated haemo-
globin. JAMA 281:1203–1210, 1999
J, Baron AD: HbA1c measurement im-
proves the detection of type 2 diabetes in
high risk individuals with non-diagnostic
levels of fasting plasma glucose. Diabetes
Care 24:465–471, 2001
29. Barrett-Connor E, Wingard DL: Normal
blood glucose and coronary
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