October 23, 20175:02 PM ET
KATHERINE
HOBSON
Undiagnosed diabetes
may not be as big of a public health problem as thought.
That's the takeaway from a study published Monday in the Annals of Internal Medicine that says that some
previous efforts have likely overestimated the number of people with undiagnosed
diabetes because they relied on a single positive test result.
By contrast, this new
measure used the American Diabetes Association's diagnostic criteria,
which recommend that people with one positive fasting blood glucose or A1C test
should have a second test to confirm a diagnosis in all but the most severe and
obvious cases of Type 2 diabetes. That's because there's some inherent
variability in the tests and because blood sugar levels fluctuate naturally
because of exercise, illness and even the time of day.
If left untreated,
Type 2 diabetes can contribute to kidney disease, nerve damage, high blood
pressure and stroke.
The Centers for Disease
Control and Prevention has applied the less stringent standard
to data from the National Health and Nutrition
Examination Survey and the U.S. Census to come up with an
estimate of 33.3 million people with diabetes in 2015, 7.2 million of whom, or
almost 24 percent, were undiagnosed. When researchers in this study applied the
stricter clinical diagnostic standard to the same data, they came up with an
estimate of 25.5 million people with diabetes, with about 2.8 million, or about
11 percent, of them undiagnosed.
"This is good
news," says Elizabeth Selvin,
a professor of epidemiology at the Johns Hopkins Bloomberg School of Public
Health and the lead author of the study. "We're doing a good job with
screening and diagnosis."
But she says that
doesn't mean diabetes isn't a public health problem, and a significant one at
that; the study found the prevalence of diabetes in the U.S. population has
risen from 5.5 percent in 1988-1994 to 10.8 percent in 2011-2014. The
proportion of undiagnosed cases has dropped from 16.3 percent over the same
period, the study found.
The difference in how
the estimates are calculated is due to the difference between epidemiological
studies, which track patterns and trends across an entire population, and
clinical practice, which focuses on individual patients. If you're just
studying historical trends, using a single-test value isn't such a big deal,
says Selvin. "But if we are focused on the burden of undiagnosed diabetes,
or the percentage of diabetes that's undiagnosed, it becomes important,"
she says. (A CDC spokeswoman says the agency doesn't directly comment on
studies that aren't its own.)
The results suggest
that public health efforts to promote screening should be focused more closely
on the people who are most likely to have undiagnosed diabetes rather than the
population as a whole. According to the study, that group includes people who
are obese, a racial or ethnic minority, and who don't have health insurance or
get regular health care. While increased age is also a risk factor, the authors
noted that there's an undiagnosed group of overweight and obese younger adults
with very high A1C levels who are likely not engaged with the health care
system and are falling through the cracks.
"We're not
missing hordes of people, which isn't to say we aren't missing some
people," says Anne Peters,
an endocrinologist and professor of medicine at the Keck School of Medicine at
USC, who wrote an editorial accompanying the study. "We need to continue
to reach out to the people who do need help."
She says more and more
programs are focused on preventing diabetes in the first place, focusing on people with
risk factors such as obesity and high cholesterol. That can
help people avoid the complications of full-blown diabetes, and the label of
having a chronic disease, which have long-term psychological effects as well as
consequences for buying life insurance and long-term care insurance, Peters
says. (And health insurance, if current Affordable Care Act rules about
pre-existing conditions should change.)
The study's authors
pointed out some limitations of their work. Among them: the data includes
fasting glucose and A1C levels taken only at one point in time, and the results
might differ if samples were taken later. And the diagnosis of diabetes depends
on study participants' self-reports, which may not be accurate.
Katherine
Hobson is a freelance health and science writer based in Brooklyn, N.Y. She's
on Twitter: @katherinehobson.
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