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[IPu] Utility of HbA1c in Preducting Diabetes Risk, Underused

Hi All,
This is from DiabetesInControl Newsletter Issue 241 Jan 5.  Looks like our
HbA1c tests could be used more widely.

Items for the Week: Utility of Hemoglobin A1c in Predicting Diabetes Risk,
on Tuesday, January 04 @ 14:47:42 EST

HbA1c testing helps predict the likelihood that patients will develop diabetes
in the future.

There is controversy surrounding the issue of whether, and how, to screen
adults for type 2 diabetes. The objective was to measure the incidence of new
diabetes among outpatients enrolled in a health care system, and to determine
whether hemoglobin A1c (HbA1c) values would allow risk stratification for
patients' likelihood of developing diabetes over 3 years.

A prospective cohort study was done with 3-year follow-up at a single large,
tertiary care, Department of Veterans Affairs Medical Center (VAMC). A
convenience sample of 1,253 outpatients without diabetes, age 45 to 64, with a
scheduled visit at the VAMC, were screened for diabetes using an initial HbA1c
measurement. All subjects with HbA1c 6.0% (normal, 4.0% to 6.0%) were invited
for follow-up fasting plasma glucose (FPG). We then surveyed patients annually
for 3 years to ascertain interval diagnosis of diabetes by a physician. The
baseline screening process was repeated 3 years after initial screening. After
the baseline screening, new cases of diabetes were defined as either the
self-report of a physician's diagnosis of diabetes, or by HbA1c 7.0% or FPG
7.0 mmol/L at 3-year follow-up. The incidence of diabetes was calculated as
the number of new cases per person-year of follow-up.

One thousand two hundred fifty-three patients were screened initially, and 56
(4.5%) were found to have prevalent unrecognized diabetes at baseline. The
1,197 patients without diabetes at baseline accrued 3,257 person-years of
follow-up. There were 73 new cases of diabetes over 3 years of follow-up, with
an annual incidence of 2.2% (95% confidence interval [CI], 1.7% to 2.7%). In a
multivariable logistic regression model, baseline HbA1c and baseline body mass
index (BMI) were the only significant predictors of new onset diabetes, with
HbA1c having a greater effect than BMI. The annual incidence of diabetes for
patients with baseline HbA1c 5.5 was 0.8% (CI, 0.4% to 1.2%); for HbA1c 5.6 to
6.0, 2.5% (CI, 1.6% to 3.5%); and for HbA1c 6.1 to 6.9, 7.8% (CI, 5.2% to
10.4%). Obese patients with HbA1c 5.6 to 6.0 had an annual incidence of
diabetes of 4.1% (CI, 2.2% to 6.0%).

>From the results it was concluded, that HbA1c testing helps predict the
likelihood that patients will develop diabetes in the future. Patients with
normal HbA1c have a low incidence of diabetes and may not require rescreening
in 3 years. However, patients with elevated HbA1c who do not have diabetes may
need more careful follow-up and possibly aggressive treatment to reduce the
risk of diabetes. Patients with high-normal HbA1c may require follow-up sooner
than 3 years, especially if they are significantly overweight or obese. This
predictive value suggests that HbA1c may be a useful test for periodic
diabetes screening.
Journal of General Internal Medicine
Volume 19 Issue 12 Page 1175 - December 2004
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