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What
is the Cutoff for impaired fasting glucose for the diagnosis of
Prediabetes?
1. A postprandial BG of over 180mg/dL.
2. A postprandial BG of over 200mg/dl
3. A postprandial BG of over 140mg/dl
4. A FPG of over 110mg/dL and below 126mg/dL.
5. A Fasting Plasma Glucose over 126mg/dL
6. A FPG of over 100mg/dL and below
126mg/dL.
7. A FPG of over 110mg/dl and or a Postprandial BG of over 140mg/dl
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The threshold for prediabetes
was lowered from 110mg/dL. to 100mg/dL.
New Revised Guidelines for PreDiabetes
will increase diagnosis of prediabetes by 20%. That will increase those
with Prediabetes by 5 million more.
Oct. 24, 2003 — An international expert committee
on the diagnosis and classification of diabetes mellitus has published
revised guidelines, which incorporate new data since the last report
of 1997, in the November issue of Diabetes Care. Decreasing the cutoff
for impaired fasting glucose from 110 mg/dL to 100 mg/dL could increase
diagnoses of prediabetes by approximately 20%.
"Lowering the threshold should help pick up more people who are
at increased risk for developing diabetes," Committee Chair Saul
Genuth, MD, from Case Western Reserve University in Cleveland, Ohio,
says in a news release. "What's important about that is that we
now know — through studies such as the Diabetes Prevention Program
(DPP) and the Finnish Diabetes Study — that we can prevent or
delay the progression to diabetes from impaired glucose tolerance, the
original component with the term pre-diabetes, through intensive lifestyle
treatment, such as exercise and diet therapy. We hope, but don't yet
know, that intervening earlier might also reduce the risk of diabetic
complications, including cardiovascular complications."
Modest weight loss and regular exercise can prevent or delay the development
of type 2 diabetes by up to 58%, based on results of the DPP and other
studies.
Criteria for the diagnosis of diabetes remain unchanged, and the committee
recommended against using the HbA1C as a routine diagnostic test for
diabetes. Although clinical evidence is currently inadequate for superiority
of either the fasting plasma glucose (FPG) test or the oral glucose
tolerance test (OGTT), the committee prefers the FPG because of its
greater convenience and lower cost.
The American Diabetes Association (ADA) recommends that individuals
aged 45 years or older, especially those who are overweight or obese,
be screened for diabetes/prediabetes and retested every three years
if normal. Individuals at increased risk because of obesity, family
history, gestational diabetes, or other recognized risk factors for
diabetes should be considered for screening every few years, according
to Dr. Genuth.
Unanswered questions mandating further research include defining the
best approach to diabetes detection, understanding the pathophysiology
and risks of IPG and glucose tolerance, and determining to what extent
cardiovascular risk can be lowered by starting treatment of glycemia
earlier.
"The answers to these and other questions will necessitate regular
surveillance and reconsideration of new data that may lead to appropriate
revisions to the diagnostic and classification criteria for diabetes
over time," the authors write.
Diabetes Care. 2003;26:3160-3167
Clinical Context
The 1997 International Expert Committee was convened to examine the
classification and diagnostic criteria of diabetes, based on the 1979
report of the National Diabetes Data group and the World Health Organization
(WHO) study group. The WHO criteria for diagnosing diabetes is FPG of
126 mg/dL or higher or two-hour plasma glucose (PG) of 200 mg/dL or
higher in the OGTT after a 75 g oral glucose challenge. The criteria
were adopted by the ADA in 1997. The two-hour PG has been considered
the de facto "gold standard" because it is a better predictor
of all-cause mortality or cardiovascular mortality than an elevated
FPG value. The FPG cutoff value is based on the prediction of retinopathy
beginning at approximately 126 mg/dL. Impaired glucose tolerance is
defined as FPG of 110 mg/dL or higher when two-hour PG after a 75 g
oral glucose challenge is 140 to 199 mg/dL. The lack of a suitable marker
of diabetes has led to a reliance on metabolic abnormalities such as
hyperglycemia to determine risk and diagnosis of diabetes.
Currently, diabetes and prediabetes screening is recommended by the
ADA for patients with risk factors for the disease including obesity,
age 45 years or older, family history, or gestational diabetes. If the
test is normal, retesting is recommended every three years. If prediabetes
or impaired glucose tolerance is diagnosed, there is a higher risk of
developing diabetes within 10 years and lifestyle modification is recommended.
The expert committee was reconvened for this position statement to reconsider
the questions of (1) cut point of the FPG and two-hour PG for diabetes
diagnosis, (2) reduction of the lower limit for impaired fasting glucose
from 110 mg/dL to 100 mg/dL, (3) inclusion of the HbA1C as a diagnostic
criterion for diabetes, and (4) use of the two-hour PG in addition to
the FPG for diagnosis of diabetes. The recommendations are based on
new studies that have emerged since 1997.
Study Highlights
The cut point for FPG and 2-hour PG will remain unchanged from 1997.
There is no consistent difference in the prevalence of diabetes across
populations observed by using the 1997 criteria. Recent studies have
not shown an advantage for reducing the 2-hour PG cut point to 180 mg/dL.
It was noted that the 2 tests measure slightly different constructs
and result in different prevalence of diabetes.
In patients with a new diagnosis of diabetes, a confirmatory test is
recommended after the initial test.
The cut point for impaired fasting glucose was reduced from a definition
of 110 mg/dL to 100 mg/dL. Impaired fasting glucose is now redefined
as an FPG of 100-125 mg/dL. This is based on observations that the receiver
operator characteristic curve closest to the ideal of 100% sensitivity
and specificity for the glycemic range of 81-126 mg/dL was 103 mg/dL
in a Dutch population, 97 mg/dL in a Pima Indian population, 94 mg/dL
in a Mauritius population, and 94 mg/dL in a San Antonio population,
all values below the older 110 mg/dL cut point.
This proposed new definition for impaired fasting glucose will increase
the number of individuals with prediabetes and thus increasing the number
of people who may benefit from intensive lifestyle modification such
as weight reduction and exercise to prevent diabetes onset.
HbA1C is not recommended as an additional criterion for the diagnosis
of diabetes. The reasons are lack of international standardization of
reference ranges and the confounding effect of other conditions (such
as pregnancy, uremia, hemoglobinopathies, blood transfusion, and hemolytic
anemia). HbA1C is still recommended as an indicator of therapeutic response.
Both FPG and 2-hour PG may be used for diagnosis, but the FPG has the
benefits of ease of testing (no waiting and better tolerated), better
reproducibility and reliability, and lower cost. There is inadequate
evidence to show that either test is superior.
The 2-hour PG is recommended after an abnormal FPG, and, if abnormal,
will lead to lower blood pressure and lipid goals compared with nondiabetic
individuals.
It is uncertain from current evidence whether treating asymptomatic
elevated 2-hour PG or changing the cut points for impaired fasting glucose
and impaired glucose tolerance will reduce mortality from cardiovascular
disease, and more research is needed in this area.
Pearls for Practice
The cut point for FPG has been reduced from 110 to 100 mg/dL, which
will increase the number of individuals diagnosed with prediabetes.
There is inadequate evidence to choose between the FPG and 2-hour PG
tests, and judgment may be based on test feasibility, reliability, and
reproducibility. Both may be performed in any one patient to confirm
diabetes diagnosis.
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