NR 601: Week 6 Quiz Review
Week 5
Diabetes
· ADA screening recommendations: when to screen to repeat screens based on
findings
Recommendations
Screening for type 2 diabetes with an informal assessment of risk factors or validated tools
should be considered in asymptomatic adults. B
Testing for type 2 diabetes in asymptomatic people should be considered in adults of any age
who are over- weight or obese (BMI >25 kg/m2 or $23 kg/m2 in Asian Americans) and who
have one or more additional risk factors for diabetes. B
For all people, testing should be- gin at age 45 years. B
If tests are normal, repeat testing carried out at a minimum of 3-year intervals is reasonable. C
To test for type 2 diabetes, fasting plasma glucose, 2-h plasma glucose after 75-g oral glucose
tolerance test, and A1C are equally appropriate. B
In patients with diabetes, identify and treat other cardiovascular disease risk factors.
Updated recommendations emphasize that testing for prediabetes and type 2 diabetes should
be considered in children and adolescents younger than 18 years of age who are overweight or
obese (BMI >85th percentile for age and sex, weight for height >85th percentile, or weight
>120% of ideal for height), and have one or more additional risk factors for diabetes such as (1)
maternal history of diabetes or gestational diabetes during the child’s gestation; (2) family
history of type 2 diabetes in first- or second-degree relative; (3) race/ethnicity (Native American,
African American, Latino, Asian American, Pacific Islander; and/or (4) signs of insulin resistance
or conditions associated with insulin resistance (acanthosis nigricans, hypertension,
dyslipidemia, polycystic ovary syndrome, or small-
DIAGNOSTIC TESTS FOR DIABETES
Diabetes may be diagnosed based on plasma glucose criteria, either the fasting plasma glucose
(FPG) or the 2-h plasma glucose (2-h PG) value after a 75-g oral glucose tolerance test (OGTT)
or A1C criteria (1,6) (Table 2.2).
FPG, 2-h PG after 75-g OGTT, and A1C are equally appropriate for diagnostic testing. It should
be noted that the tests do not necessarily detect diabetes in the same individuals. The efficacy
of
interventions for primary prevention of type 2 diabetes (7,8) has primarily been demonstrated
among individuals with impaired glucose tolerance (IGT), not for individuals with isolated
impaired fasting glucose (IFG) or for those with prediabetes defined by A1C criteria.
The same tests may be used to screen for and diagnose diabetes and to detect individuals with
prediabetes. Diabetes may be identified anywhere along the spectrum of clinical scenarios: in
seemingly low-risk individuals who happen to have glucose testing, in individuals tested based
on diabetes risk assessment, and in symptomatic patients.
,Fasting and 2-Hour Plasma Glucose
The FPG and 2-h PG may be used to diagnose diabetes (Table 2.2). The concordance between
the FPG and 2-h PG tests is imperfect, as is the concordance be- tween A1C and either
glucose-based test. Numerous studies have confirmed that, compared with FPG and A1C cut
points, the 2-h PG value diagnoses more people with diabetes.
A1C
The A1C test should be performed using a method that is certified by the NGSP (www.ngsp.org)
and standardized or traceable to the Diabetes Control and Complications Trial (DCCT)
reference as- say. Although point-of-care A1C assays may be NGSP certified, proficiency
testing is not mandated for performing the test, so use of point-of-care assays for diagnostic
purposes is not recommended but may be considered in the future if proficiency testing is
performed and documented.
The A1C has several advantages com- pared with the FPG and OGTT, including greater
convenience (fasting not required), greater preanalytical stability, and less day-to-day
perturbations during stress and illness. However, these
advantages may be offset by the lower sensitivity of A1C at the designated cut point, greater
cost, limited availability of A1C testing in certain regions of the developing world, and the
imperfect correlation between A1C and average glucose in certain individuals. National Health
and Nutrition Examination Survey (NHANES) data indicate that an A1C cut point of $6.5% (48
mmol/mol) identifies one-third fewer cases of undiagnosed diabetes than a fasting glucose cut
point of $126 mg/dL (7.0 mmol/L) (9).
When using A1C to diagnose diabetes, it is important to recognize that A1C is an indirect
measure of average blood glucose levels and to take other factors into consideration that may
impact hemoglobin glycation independently of glycemia including age, race/ethnicity, and
anemia/ hemoglobinopathies.
Confirming the Diagnosis
Unless there is a clear clinical diagnosis (e.g., patient in a hyperglycemic crisis or with classic
symptoms of hyperglycemia and a random plasma glucose $200 mg/dL [11.1 mmol/L]), a
second test is required for confirmation. It is recommended that the same test be repeated
without delay using a new blood sample for confirmation because there will be a greater
likelihood of concurrence. For ex- ample, if the A1C is 7.0% (53 mmol/mol) and a repeat result
is 6.8% (51 mmol/mol), the diagnosis of diabetes is confirmed. If two different tests (such as
A1C and FPG) are both above the diagnostic threshold, this also confirms the diagnosis. On the
other hand, if a patient has discordant results from two different tests, then the test result that is
above the diagnostic cut point should be repeated. The diagnosis is made on the basis of the
confirmed test. For example, if a patient meets the diabetes criterion of the A1C (two results
$6.5% [48 mmol/mol]) but not
FPG (,126 mg/dL [7.0 mmol/L]), that person should nevertheless be considered to have
diabetes.
Since all the tests have preanalytic and analytic variability, it is possible that an abnormal result
(i.e., above the diagnostic threshold), when repeated, will produce a value below the diagnostic
, cut point. This scenario is likely for FPG and 2-h PG if the glucose samples remain at room
temperature and are not centrifuged promptly. Because of the potential for preanalytic
variability, it is critical that samples for plasma glucose be spun and separated immediately after
they are drawn. If patients have test results near the margins of the diagnostic threshold, the
health care professional should follow the patient closely and repeat the test in 3–6 months.
Description
In 1997 and 2003, the Expert Committee on the Diagnosis and Classification of Diabetes
Mellitus (17,18) recognized a group of individuals whose glucose levels did not meet the criteria
for diabetes but were too high to be considered nor- mal. “Prediabetes” is the term used for
individuals with IFG and/or IGT and/or A1C 5.7–6.4% (39–47 mmol/mol). Pre- diabetes should
not be viewed as a clinical entity in its own right but rather as an increased risk for diabetes
(Table 2.3) and cardiovascular disease (CVD). Prediabetes is associated with obesity
(especially abdominal or visceral obesity), dyslipidemia with high triglycerides and/or low HDL
cholesterol, and hypertension.
Diagnosis
The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus (17,18) defined
IFG as FPG levels be- tween 100 and 125 mg/dL (between 5.6 and 6.9 mmol/L) and IGT as 2-h
PG after 75-g OGTT levels between 140 and 199 mg/dL (between 7.8 and 11.0 mmol/L). It
should be noted that the World Health Organization (WHO) and numerous other diabetes
organizations define the IFG cutoff at 110 mg/dL (6.1 mmol/L).
As with the glucose measures, several prospective studies that used A1C to predict the
progression to diabetes as defined by A1C criteria demonstrated a strong, continuous
association between A1C and subsequent diabetes. In a systematic review of 44,203 individuals
from 16 cohort studies with a follow-up interval averaging 5.6 years (range 2.8– 12 years), those
with A1C between 5.5 and 6.0% (between 37 and 42 mmol/mol) had a substantially increased
risk of diabetes (5-year incidence from 9 to 25%). An A1C range of 6.0–6.5% (42–48 mmol/mol)
had a 5-year risk of developing diabetes between 25 and 50% and a relative risk 20 times
higher compared with A1C of 5.0% (31 mmol/mol) (19). In a community- based study of African
American and non-Hispanic white adults without diabetes, baseline A1C was a stronger
predictor of subsequent diabetes and cardiovascular events than fasting glucose (20). Other
analyses suggest that A1C of 5.7% (39 mmol/mol) or higher is associated with a diabetes risk
similar to that of the high-risk participants in the Diabetes Prevention Program (DPP) (21), and
A1C at baseline was a strong predictor of the development of glucose- defined diabetes during
the DPP and its follow-up (22).
Hence, it is reasonable to consider an A1C range of 5.7–6.4% (39–47 mmol/mol) as identifying
individuals with prediabetes. Similar to those with IFG and/or IGT, individuals with A1C of 5.7–
6.4% (39– 47 mmol/mol) should be informed of their increased risk for diabetes and CVD and
counseled about effective strategies to lower their risks (see Section 5 “Prevention or Delay of
Type 2 Diabetes”). Similar to glucose measurements, the continuum of risk is curvilinear, so as
A1C rises, the diabetes risk rises disproportionately (19). Aggressive interventions and vigilant
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