section 22.8
Abnormalities of Metabolic Homeostasis
T A B L E 2 2 - 5
Criteria for the Diagnosis o f Diabetes Mellitus
1. Symptoms of diabetes plus casual plasma glucose
concentration >200 mg/dl (11.1 mmol/1). Casual is
defined as any time of day without regard to time
since last meal. The classic symptoms of diabetes
include polyuria, polydipsia, and unexplained weight
2. FPG >126 mg/dl (7.0 mmol/1). Fasting is defined as
no caloric intake for at least
3. 2hPG >200 mg/dl during an OGTT. The test should
be performed as described by WHO using a glucose
load containing the equivalent of 75-g anhydrous
glucose dissolved in water.
In the absence of unequivocal hyperglycemia with acute metabolic de-
compensation, these criteria should be confirmed by repeat testing on a
different day. The third measure (OGTT) is not recommended for rou-
tine clinical use.
FPG = Fasting plasma glucose; OGTT = Oral glucose tolerance test;
2hPG = 2 hour post load glucose. The diagnostic criteria are based upon
the report by the Expert committee on the diagnosis and classification
of Diabetes mellitus.
D ia b e te s C a re
24(suppl. 1), 55 (2001).
in Table 22-5. Subjects who have fasting plasma glucose
levels between >110 mg/dL and <126 mg/dL are said to
have impaired glucose tolerance and may require addi-
tional as well as periodic testing.
The diagnosis of gestational diabetes mellitus consists
of two parts. A screening glucose challenge test is per-
formed between 24 and 28 weeks of gestation after the
oral administration of 50-g of glucose. This test is per-
formed at any time of the day and irrespective of food
intake. If the plasma glucose after the 50-g challenge is
>140 mg/dL (7.8 mmol/L), the test is considered positive
and requires a diagnostic test consisting of oral ingestion
1 0 0
g of glucose after a fasting for
hours, followed
by 3-hour oral glucose tolerance test (Table 22-6). In the
50-g challenge test, if the threshold for the abnormality
is decreased to >130 mg/dL (7.2 mmol/L), the sensitivity
for identifying patients with gestational diabetes mellitus
increases from 80% to 90%.
Since diabetes mellitus is an insidious disorder, testing
of asymptomatic patients may be desirable under certain
conditions, including age 45 years or older; obesity; first-
degree relatives of diabetics; members of high-risk eth-
nic population (e.g., Native American, Hispanic, African-
American); women who have delivered an infant weighing
more than 9 lb (4.08 kg) or have had gestational diabetes
mellitus; hypertension; abnormal lipid studies; recurring
T A B L E 2 2 - 6
Screening and Diagnosis Scheme for Gestational Dia-
betes Mellitus (GDM)
Screening Test
Diagnostic Test
95 mg /dl
140 mg/dl
180 mg/dl
155 mg/dl
140 mg/dl
Screening for GDM may not be necessary in pregnant women who
meet all of the following criteria: <25 years of age, normal body
weight, no first degree relative with diabetes, and not Hispanic,
Native-American, Asian-, or African-American. The 100-g diagnostic
test is performed on patients who have a positive screening test. The
diagnosis of GDM requires any two of the four plasma glucose values
obtained during the test to meet or exceed the values shown above. To
convert values for glucose to mmol/ L, multiply by 0.05551. The diag-
nostic criteriais based upon the report by the American Diabetes
Association on Gestational Diabetes Mellitus.
D ia b e te s C a re
23(suppl. 1), S77 (2000).
skin, genital, or urinary tract infections; and previous im-
paired glucose intolerance.
After the diagnosis of diabetes mellitus has been made
and with the initiation of appropriate therapy (discussed
later), assessment of other biochemical parameters is nec-
essary in the management phase of the disorder to main-
tain the fasting blood glucose level as close to normal as
possible and to prevent long-term complications. These
biochemical tests include measurement of a stable form
of glycosylated hemoglobin (hemoglobin AJc), determi-
nation of urine albumin excretion rate, measurement of
serum fructosamine levels, and self-monitoring of blood
glucose levels. Hemoglobin Aic levels are used to assess
average glucose control over a 2 to 3-month period, since
the red blood cell’s life span is ahout
1 2 0
days. Entty_of
glucose into red blood cells depends only on the prevailing
plasma glucose concentration. (Formation of hemoglobin
Aic, which is nonenzymatic, is discussed in Chapters 2 and
10). The normal hemoglobin Alc concentration is about
4—6%; spurious values for hemoglobin AJc levels can oc-
cur in uremic states, hemoglobinopathies (Chapter 28),
hemolytic anemia and blood transfusion. Fructosamine is
a generic term applied to the stable condensation product
of glucose with serum proteins (albumin, with a circulat-
ing half-life of about
2 0
days, is the major contributor).
Thus, serum fructosamine levels reflect glucose control
over a period of 2-3 weeks.
One of the chronic complications of diabetes melli-
tus is diabetic nephropathy, which leads to end-stage re-
nal disease. An initial biochemical parameter of diabetic
nephropathy in the asymptomatic state is a persistent
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