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Using A1c Test is Cost-Effective to Diagnose Prediabetes

Posted: Monday, March 26, 2012

Using A1c to catch prediabetes is cost-effective if the threshold for diagnosis is set at 5.7%.

The cost of treating patients for an HbA1c level less than 5.7% would likely outweigh the savings from improvement in long-term outcomes, according to an analysis by Xiaohui Zhuo, PhD, of the CDC in Atlanta, and colleagues largely at the same agency.

Those diagnostic cutoffs wouldn't fall within the $50,000 per quality life-year gained, typically considered cost-effective.

"Lowering the cutoff from 5.7% to 5.6% also may be cost effective, however, if the costs of preventive interventions were to be lowered," the group noted.

The threshold for diagnosing prediabetes became controversial in 2009, when the American Diabetes Association recommended using hemoglobin A1c as the new standard diagnostic test for diabetes and prediabetes.

That organization indicated 6.5% as the cutoff for frank diabetes, but the level indicating prediabetes has variably been set anywhere from 6.0% to 5.5% by different professional groups.

"Establishing an A1c cutoff for prediabetes, however, has been more challenging than for diabetes because the relationship between the incidence of type 2 diabetes and A1c below 6.5% is continuous, with no clearly demarcated threshold that is associated with an accelerated risk of diabetes or other morbidities," Zhou's group explained.

They ran simulations using a nationally-representative sample of the nondiabetic adult population in the National Health and Nutritional Examination Survey (NHANES 1999 to 2006), modeling the impact of each 0.1% increment in the threshold for prediabetes from 6.4% to 5.5%.

Each lower threshold progressively improved health of the population considered over a lifetime from the healthcare system perspective but also increased costs.

Assuming that prediabetes found in that population was treated with a higher-cost approach similar to that seen in the Diabetes Prevention Program study averaging about $1,000 a year, moving the cutoff for prediabetes diagnosis as low as 5.7% was cost-effective.

The cost per quality life-year gained was:

$27,000 to go from 6.0% to 5.9%
$34,000 to further drop from 5.9% to 5.8%
$45,000 to go from 5.8% to 5.7%

But bringing the threshold for diagnosis down further exceeded the $50,000 mark per quality life-year gained, at $58,000 to go from 5.7% to 5.6% and $96,000 to go from 5.6% to 5.5%.

The numbers were better assuming use of lower cost interventions averaging about $300 per year to treat prediabetes as in the Promoting a Lifestyle of Activity and Nutrition for Working to Alter the Risk of Diabetes (PLAN4WARD) study.

The cost per quality life-year gained in that analysis was just $24,000 to lower the HbA1c cutoff from 6.0% to 5.9% and $34,000 to get down to 5.7%.

Even going from 5.7% to 5.6% would be considered cost-effective in that less expensive scenario, costing $43,000 per quality life year gained, although the next increment to 5.6% wasn't at $70,000.

The group cautioned that use of hemoglobin A1c for diagnosis isn't universally agreed upon and does have some limitations.

Practice Pearls:

Point out that this study using a simulation model suggests that lowering the A1c cutoff for prediabetes to 5.7% would be cost effective.
The American Diabetes Association recommended adoption of hemoglobin HbA1c testing for identifying diabetes and prediabetes and an HbA1c value of 6.5% was selected as the diagnostic cutoff.

Source: http://www.diabetesincontrol.com/index.php?option=com_content&view=article&id=12418&catid=53&Itemid=8, Zhuo X, et al "Alternative HbA1c cutoffs to identify high-risk adults for diabetes prevention: a cost-effectiveness perspective" Am J Prev Med 2012; DOI: 10.1016/j.amepre.2012.01.003.