Results from a novel study demonstrated that lowering the glycosylated hemoglobin cutoff for prediabetes leads to less cost-effective preventive interventions.
The study, which used a simulation sample of U.S. adults from the NHANES (National Health and Nutrition Examination Survey) from 1999 to 2006, found that the cost per quality-adjusted life-year (QALY) associated with an HbA1c cutoff of 5.7% or higher was identified as being below $50,000 per QALY, "a widely recognized threshold for the cost-effective use of [health care] resources," wrote the researchers, who reported their findings in the April issue of the American Journal of Preventive Medicine.
Led by Xiaohui Zhuo, Ph.D., of the division of diabetes translation at the National Center for Chronic Disease Prevention and Health Promotion, the researchers used a Markov simulation model to assess the cost-effectiveness associated with a progressive 0.1% decrease in the HbA1c cutoff from 6.4% to 5.5%. "Previous studies have evaluated the cost-effectiveness of interventions to prevent type 2 diabetes," the researchers wrote. "However, no study has compared the cost-effectiveness of type 2 diabetes preventive intervention when using alternative HbA1c cutoffs to determine eligibility for intervention."
Establishment of an HbA1c cutoff for prediabetes, however, has been more challenging than that for diabetes because the relationship between the incidence of type 2 diabetes and HbA1c below 6.5% is continual, 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%.
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% (Am. J. Prev. Med. 2012;42:374-81).
The simulation sample included NHANES participants who had baseline HbA1c values below 6.5%. Analysis was conducted under two scenarios for type 2 diabetes prevention interventions: a high-cost intervention, as implemented in the Diabetes Prevention Program (DPP) clinical trial, which costs about $1,000 per year, and a low-cost intervention as implemented in the PLAN4WARD (Promoting a Lifestyle of Activity and Nutrition for Working to Alter the Risk of Diabetes) study, which costs about $300 per year.
The following costs were considered: the cost of a one-time HbA1c test for all participants; the costs of lifestyle interventions, annual screening tests, and the associated direct medical costs for people with prediabetes; and – after the diagnosis of type 2 diabetes – the direct medical costs of type 2 diabetes and diabetes-related complications. Direct medical cost associated with prediabetes was based on the DPP, and costs were expressed in 2009 dollars.
The simulation analysis was performed under two scenarios for type 2 diabetes–preventive interventions: a high-cost lifestyle intervention as implemented in the DPP clinical trial, and a low-cost lifestyle intervention as implemented in the PLAN4WARD study.
Dr. Zhuo and associates determined that in the high-cost intervention, lowering the HbA1c cutoff from 6.0% to 5.9% would cost $27,000 per QALY gained, whereas lowering the cutoff from 5.9% to 5.8% would cost $34,000 per QALY gained. In addition, they found that lowering the HbA1c 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.
In the low-cost intervention, the researchers determined that lowering the HbA1c cutoff from 6.0% to 5.9% would cost $24,000 per QALY gained, whereas lowering the cutoff from 5.9% to 5.8% would cost $27,000 per QALY gained. In addition, they found that lowering the HbA1c from 5.8% to 5.7%, from 5.7% to 5.6%, and from 5.6% to 5.5% would cost $34,000, $43,000, and $70,000 per QALY gained, respectively.
"Assuming a conventional cost-effectiveness benchmark of $50,000 [per QALY], setting the HbA1c cutoff at no lower than 5.7% was found to be cost effective," Dr. Zhuo and associates wrote. "However, 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 researchers acknowledged certain limitations of the study, including the fact that the analysis did not include other measures, such as fasting plasma glucose and body mass index; that the population studied was restricted to middle-aged and elderly adults; and that study participants who were identified as having prediabetes "were assumed to receive the same lifestyle intervention and to attain the same relative diabetes risk reduction regardless of baseline HbA1c level."
This study used data from a trial supported by the National Heart, Lung, and Blood Institute. Dr. Zhuo and associates stated that they had no relevant financial conflicts to disclose.