Research article
Alternative HbA1c Cutoffs to Identify High-Risk Adults for Diabetes Prevention: A Cost-Effectiveness Perspective

https://doi.org/10.1016/j.amepre.2012.01.003Get rights and content

Background

New recommendations about the use of hemoglobin A1c (HbA1c) for diagnosing diabetes have stimulated a debate about the optimal HbA1c cutoff to identify prediabetes for preventive intervention.

Purpose

To assess the cost effectiveness associated with the alternative HbA1c cutoffs for identifying prediabetes.

Methods

A Markov simulation model was used to examine the cost effectiveness associated with a progressive 0.1% decrease in the HbA1c cutoff from 6.4% to 5.5%. The target population was the U.S. nondiabetic population aged ≥18 years. The simulation sample was created using the data of nondiabetic American adults from the National Health and Nutritional Examination Survey (NHANES 1999–2006). People identified as having prediabetes were assumed to receive a preventive intervention, with effectiveness the same as that in the Diabetes Prevention Program study under a high-cost intervention (HCI) scenario and in the Promoting a Lifestyle of Activity and Nutrition for Working to Alter the Risk of Diabetes study under a low-cost intervention (LCI) scenario. The analysis was conducted for a lifetime horizon from a healthcare system perspective.

Results

Lowering the HbA1c cutoff would increase the health benefits of the preventive interventions at higher costs. For the HCI, lowering the HbA1c cutoff from 6.0% to 5.9% and from 5.9% to 5.8% would result in $27,000 and $34,000 per QALY gained, respectively. Continuing to decrease the cutoff from 5.8% to 5.7%, from 5.7% to 5.6%, and from 5.6% to 5.5% would cost $45,000, $58,000, and $96,000 per QALY gained, respectively. For the LCI, lowering the HbA1c cutoff 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. Continuing to lower 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.

Conclusions

Lowering the HbA1c cutoff for prediabetes leads to less cost-effective preventive interventions. Assuming a conventional $50,000/QALY cost-effectiveness benchmark, the HbA1c cutoffs of 5.7% and higher were found to be 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.

Introduction

In 2010, the American Diabetes Association (ADA) recommended adoption of hemoglobin HbA1c testing as one basis for identifying diabetes and prediabetes.1 Under the recommendation, an HbA1c value of 6.5% was selected as the diagnostic cutoff for diabetes. This selection was based on observations of an accelerated risk of diabetes-related microvascular complications.2 This recommendation has stimulated a debate about what HbA1c cutoff should be used to define the high-risk state, sometimes referred to as prediabetes, to determine the eligibility for intervention.3, 4, 5, 6, 7, 8 Establishing an HbA1c cutoff for prediabetes, however, has been more challenging than for diabetes because the 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. Therefore, the debate continues over what HbA1c level should be used to define prediabetes, and professional organizations have independently recommended at least three different cutoffs—6.0%, 5.7%, and 5.5%.2, 9, 10

Selecting an accepted HbA1c cutoff for defining prediabetes would determine eligibility for receiving diabetes-preventive interventions and, thus, ultimately affects the cost effectiveness of interventions. A lower HbA1c cutoff might result in a less cost-effective intervention, because a larger number of false positives would lead to intervening among many individuals at a lower risk for type 2 diabetes and thus less likely to benefit. However, it also would result in a larger number of individuals being eligible for intervention, which might produce a greater societal health benefit. Conversely, a higher cutoff might lead to greater cost effectiveness, but fewer cases of diabetes would be prevented.

Previous studies11 have evaluated the cost effectiveness of interventions to prevent type 2 diabetes. However, no study has compared the cost effectiveness of type 2 diabetes–preventive intervention when using alternative HbA1c cutoffs to determine eligibility for intervention. The goal of the current 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%.

Section snippets

Methods

A prediabetes/type 2 diabetes simulation model was employed for this analysis. The model was originally developed by the CDC and Research Triangle Institute International.12, 13, 14, 15 The model has a Markov structure and includes the annual transition probabilities between health states. The model has been used to evaluate the lifestyle intervention in the Diabetes Prevention Program (DPP)13 as well as other interventions designed to manage risk factors for diabetes-related complications

Results

Figure 1 illustrates the comparison of cost per QALY gained among the HbA1c cutoffs. Lowering the HbA1c cutoff would increase the QALY gains but at higher costs. Under the HCI (panel A in Figure 1), compared with an HbA1c cutoff of 6.4%, using an HbA1c cutoff of 6.3% would cost $16,000 more per QALY gained. The cost per QALY gained would continue to increase with each successive 0.1% decrease in the HbA1c cutoff from 6.3% to 5.5%. For example, decreasing the cutoff from 6.0% to 5.9% and from

Discussion

Large-scale implementation of evidence-based type 2 diabetes prevention depends on a clear and efficient strategy to identify individuals at high risk for type 2 diabetes and refer them for intervention. New recommendations call for the adoption of an HbA1c measure for identifying individuals at high risk, but the optimal HbA1c cutoff for such efforts remains unclear. This study is the first study of which the authors are aware that examines the impact and cost effectiveness of using

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