Doctors who give their afternoon patients the fasting
plasma glucose test are likely to miss half of the diabetes
cases in this group, according to research published in
"The Journal of the American Medical Association" on
27 December 2000. The American Diabetes Association currently
recommends the fasting plasma glucose test for detecting
type 2 diabetes. The test is diagnostic for diabetes if a
person has a blood glucose level of 126 milligrams per
deciliter (mg/dl) or higher, and a second test on another
day confirms the same high level of blood glucose.
The recommendation is based on studies of plasma glucose
measured in the morning after an 8-hour fast. However,
many patients are seen in the afternoon after variable
periods of fasting. In the "JAMA" study, researchers from
the National Institute of Diabetes and Digestive and Kidney
Diseases (NIDDK) and Social and Scientific Systems, Inc.,
analyzed fasting plasma glucose levels taken at different
times of day from adults participating in the Third
National Health and Nutrition Examination Survey (NHANES
III) conducted from 1988 to 1994. The researchers
compared the plasma glucose levels of 6,483 people tested
in the morning after a median fasting time of 13.5 hours to
the glucose levels of 6,399 people tested in the afternoon
after a median fasting time of 7 hours. Participants in
both groups were otherwise similar in age, sex, race,
weight, physical activity, waist-to-hip ratio, family
history of diabetes, and other factors that may affect
blood glucose levels.
The researchers found that fasting plasma glucose levels
were consistently higher in the morning group compared to
the afternoon, with an overall mean difference of 5 mg/dl.
Moreover, the afternoon patients had blood glucose levels
suggestive of diabetes at half the rate of the morning
group. "If the current recommended criteria for diagnosing
diabetes were applied to the afternoon patients, about half
the cases of diabetes would be missed," says NIDDK's Dr.
To accurately detect diabetes in afternoon patients, the
researchers suggest that the diagnostic standard of glucose
levels for this group should be lower--114 mg/dl or greater
instead of the current standard of 126 mg/dl or greater.
In any case, the researchers advise physicians to confirm
the diagnosis by repeat testing on a different day,
preferably in the morning.
About 16 million people in the United States have diabetes,
the most common cause of blindness, kidney failure, and
amputations in adults. Type 2 accounts for about 90
percent of diabetes cases in the United States, and a third
of these cases are undiagnosed. Type 2 is most common in
people who are overweight, inactive, age 40 and older, and
have a family history of diabetes. The disease is also
more common in minorities: African Americans,
Hispanic/Latino Americans, American Indians, and some Asian
Americans and Pacific Islanders are at particularly high
risk for type 2. Many people can control their blood
glucose by following a careful diet and exercise program,
losing excess weight, and taking oral medication. However,
the longer a person has type 2 diabetes, the more likely he
or she will need insulin injections, either alone or
combined with oral drugs.
About 10 percent, or 1.6 million of people with diabetes,
have type 1, formerly known as juvenile onset diabetes or
insulin-dependent diabetes. This form of diabetes, which
usually occurs in children and adults under age 30,
develops when the body's immune system attacks the insulin-
producing cells of the pancreas.