HbA1c Threshold of 5.7% Cost-Effective as Prediabetes Screen

Elizabeth DeVita-Raeburn

March 14, 2012

March 14, 2012 — Setting the hemoglobin A1c (HbA1c) threshold to 5.7% when screening for prediabetes would be a cost-effective strategy for making more people eligible for interventions to prevent progression to type 2 diabetes, according to a study published in the April issue of the American Journal of Preventive Medicine.

The American Diabetes Association recommends HbA1c testing as a criterion by which to diagnose diabetes and prediabetes. However, although an HbA1c value of 6.5% has been established as the diagnostic figure associated with diabetes, a similarly clear-cut number designating risk for prediabetes has remained elusive.

"[T]he relationship between the incidence of type 2 diabetes and HbA1c below 6.5% is continuous, with no clearly demarcated threshold that is associated with an accelerated risk of diabetes or other morbidities," write lead author Xiaohui Zhuo, PhD, from the Division of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, and colleagues.

At least 3 different professional organizations have recommended 3 different cutoffs: 6.0%, 5.7%, and 5.5%.

The goal of this study "was to examine the change in the cost effectiveness of diabetes-preventive interventions because of progressive 0.1% decremental reductions in the HbA1c cutoff from 6.4% to 5.5%," the authors write.

The researchers used a simulation model developed by the Centers for Disease Control and Prevention and Research Triangle Institute International, using data from nondiabetic adults enrolled in the National Health and Nutritional Examination Survey from 1999 to 2006.

Individuals identified as having prediabetes were assumed to receive either a high-cost intervention that costs almost $1000 per year or a low-cost intervention with an annual cost of $300 per year. The simulation analysis was performed using each of these 2 scenarios.

For the high-cost intervention (HCI), lowering HbA1c from 6.0% to 5.9% cost $27,000 per quality-adjusted life-year (QALY) gained. Similarly, using the HCI scenario, reducing HbA1c from 5.9% to 5.8% cost $34,000 per QALY gained, and $45,000, $58,000, and $96,000 per QALY gained for lowering HbA1c from 5.8% to 5.7%, 5.7% to 5.6%, and 5.6% to 5.5%, respectively.

For the low-cost intervention (LCI), lowering HbA1c from 6.0% to 5.9% and from 5.9% to 5.8% would result in $24,000 and $27,000 per QALY gained, respectively. Further lowering of the cutoff from 5.8% to 5.7%, 5.7% to 5.6%, and 5.6% to 5.5% "would cost $34,000, $43,000 and $70,000 per QALY gained, respectively," the authors write.

Based on a $50,000/QALY benchmark, HbA1c cutoffs of 5.7% and above were deemed cost-effective using either the LCI or HCI scenario. The QALY is "a widely recognized threshold for the cost-effective use of healthcare resources," the authors write. They add that lowering the cutoff from 5.7% to 5.6% or even lower also might be cost-effective, if the costs of preventive interventions could be reduced.

The limitations of the study included that the population characteristics and health profiles of the participants might not be representative of the population at large. The analysis was also restricted to middle-aged and elderly adults. As the cost per QALY increased with age, the researchers may have underestimated the cost-effectiveness of the interventions in younger age groups. The analysis also did not include the use of measures other than HbA1c, such as body mass index, that might be used to determine eligibility for diabetes intervention programs.

This research uses data from the Atherosclerosis Risk in Communities Study, which is supported by National Heart, Lung, and Blood Institute. The authors have disclosed no relevant financial relationships.

Am J Prev Med. 2012;42:374-381. Full text