A1c testing as a screen for Impaired Glucose Tolerance and Diabetes – potential for anti-selection?

by Betsy on October 7, 2010

Many clients are currently including A1c as part of a screening blood profile, but those that aren’t may be leaving themselves open to anti-selection. Multiple internal A1c pilots have shown that anywhere from 8-33% of applicants with normal serum glucose, fructosamine, and urine glucose will have A1c > 6%.

The American Diabetes Association recently published new guidelines for diagnosing and treating Diabetes as a supplement to the January issue of Diabetes Care (http://care.diabetesjournals.org/content/33/Supplement_1). One of the biggest changes was the recommendation that A1c now be used to diagnose pre-diabetes and diabetes. Studies have shown that approximately 25% of type 2 diabetics do not know that they have the disease. And more efforts need to be made to screen for the disease. There are numerous advantages to using A1c to perform screening.  A1C is a better index of glycemic exposure than blood glucose, is at least as good at predicting risk of long-term complications, has similar if not better standardization, and is better in its lack of day to day variability. The new ADA guidelines suggest who should be tested for diabetes, and with the renewed emphasis on preventative medicine they will likely be followed by most primary care physicians. The guidelines suggestion on who should be tested is as follows:

Criteria for testing for diabetes in asymptomatic adult individuals

  1. Testing should be considered in all adults who are overweight (BMI _25 kg/m2*) and have additional risk factors:
    • physical inactivity
    • first-degree relative with diabetes
    • members of a high-risk ethnic population (e.g., African American, Latino, Native American, Asian American, Pacific Islander)
    • women who delivered a baby weighing _9 lb or were diagnosed with GDM
    • hypertension (_140/90 mmHg or on therapy for hypertension)
    • HDL cholesterol level _35 mg/dl (0.90 mmol/l) and/or a triglyceride level _250 mg/dl (2.82 mmol/l)
    • women with polycystic ovary syndrome
    • A1C _5.7%, IGT, or IFG on previous testing
    • other clinical conditions associated with insulin resistance (e.g., severe obesity,acanthosis nigricans)
    • history of CVD
  2. In the absence of the above criteria, testing diabetes should begin at age 45 years
  3. If results are normal, testing should be repeated at least at 3-year intervals, with consideration of more frequent testing depending on initial results and risk status.” (1) The new guidelines also state that: “Individuals with an A1C of 5.7–6.4% should be informed of their increased risk for diabetes as well as cardiovascular disease and counseled about effective strategies, such as weight loss and physical activity, to lower their risks. As with glucose measurements, the continuum of risk is curvilinear, so that as A1C rises, the risk of diabetes rises disproportionately. Accordingly, interventions should be most intensive and follow-up should be particularly vigilant for those with A1C levels above 6.0%, who should be considered to be at very high risk.” (2) One prospective study showed that 88% or those with A1c 5.7-6.4% will develop diabetes within 6 years without weight loss or exercise programs. Regarding the diagnosis of diabetes, the guidelines state: “A1C assays are now highly standardized so that their results can be uniformly applied both temporally and across populations. In their recent report, an International Expert Committee, after an extensive review of both established and emerging epidemiological evidence, recommended the use of the A1C test to diagnose diabetes, with a threshold of _6.5%, and ADA affirms this decision. The diagnostic A1C cut point of 6.5% is associated with an inflection point for retinopathy prevalence…” (2) These new ADA guidelines will likely result in more individuals being aware of their A1c value, and if it is elevated, they might be in a position to anti-select against companies who are not testing.

References:

  1. Diabetes Care January 2010 33:S11-S61
  2. Diabetes Care January 2010 33:S62-S69

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