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International Journal for Quality in Health Care 15:283-285 (2003)
© 2003 International Society for Quality in Health Care

Editorial

Setting evidence-based priorities for diabetes care improvement

Patrick J. O'Connor

Senior Clinical Investigator, HealthPartners Research Foundation PO Box 1524, Minneapolis, MN, USA

A decade ago, only about one-third of adults with diabetes had acceptable levels of glycemic control [1]. In this issue of International Journal for Quality in Health Care, a report from Sweden demonstrates that ~60% of adults with diabetes have achieved acceptable levels of glycemic control [measured as glycated hemoglobin (HbA1c)], as defined according to national guidelines [2]. Reports from various other settings also show improved levels of glycemic control. For example, median HbA1c reached 6.9% in one managed care population in Minnesota in 2001 [3], and others [4–9] have reported similarly good levels of HbA1c. Although substantive issues related to measurement of HbA1c remain, there is little doubt that widespread improvement in glycemic control has occurred since the publication of the Diabetes Control and Complications Trial in 1993 [10].

To assess progress in diabetes care, however, it is not sufficient to focus only upon glycemic control [11]. About 75% of those with type 2 diabetes die from macrovascular complications, including heart attack and stroke [12]. These macrovascular complications of diabetes also account for the majority of excess health care costs associated with diabetes [13,14]. Although epidemiological evidence links elevated HbA1c to macrovascular complications [6], clinical trials have not yet proven that HbA1c lowering significantly reduces the risk of heart attacks or strokes [15,16]. On the other hand, many clinical trials show that control of hypertension, control of lipid disorders, and aspirin use substantially reduce cardiovascular morbidity or mortality in those with diabetes. Therefore, cardiovascular risk factor control deserves high priority in evaluating the overall quality of diabetes care.

The importance of blood pressure control, lipid control, and aspirin use increases as the proportion of patients with acceptable glycemic control increases. Thus, in populations where the median A1c is within 1.5% of normal, a shift in focus of diabetes quality improvement efforts from glycemic control to other important dimensions of diabetes care should be carefully considered. There is a tendency to continue to focus on HbA1c, and to attempt to drive the population HbA1c even lower, without considering the opportunity costs of such a strategy. In the setting of improved glycemic control, a strong clinical and economic argument [17,18] can be made for much greater emphasis on blood pressure control [20], lipid control [21], and aspirin use [22].

Blood pressure control is of particular importance for several reasons. Firstly, the UK Prospective Diabetes Study Group (UKPDS) study demonstrated that a 10 mm drop in systolic blood pressure was superior to a drop in HbA1c from 8% to 7.1% for the reduction of both microvascular and macrovascular complications [15,16]. Secondly, in the Hypertension Optimal Treatment (HOT) study, lowering diastolic blood pressure to 80 mm Hg appeared to significantly improve outcomes for adults with diabetes [23]. Thirdly, the use of blood pressure medications such as angiotensin-converting enzyme inhibitors [24,25] or chlorthalidone [26] reduce cardiovascular events in adults with diabetes.

In most care settings, the gap between observed and recommended levels of blood pressure exceeds the gap between observed and recommended levels of HbA1c. For example, in today's report from Sweden, while 59% had good or acceptable HbA1c, only 23% of those receiving hypertension medications had blood pressure levels of <=140/85 mm Hg. This gap would be even worse if it were measured against the current blood pressure goal of <130/80 mm Hg. In settings with reasonably good levels of glycemic control (HbA1c level within 1.5% of upper normal), the most effective and efficient way to reduce both macrovascular and microvascular complications may be to direct increasing attention to blood pressure control, while maintaining efforts to improve glycemic control.

An economic argument can also be made for the precedence of blood pressure control over glycemic control as a quality improvement goal for adults with type 2 diabetes. A recent analysis by a panel of experts at the U.S. Centers for Disease Control shows that in those with diabetes, blood pressure reduction is a much more efficient way to maximize quality adjusted life years (QALY) than either glycemic control or lipid control. Glycemic control averaged approximately $41 384 per QALY, and increased to $154 376 for patients aged 65–74 years. Lipid control averaged $51 889 per QALY. Blood pressure control, in contrast, was cost saving at all ages up to 85 years. Blood pressure control was more cost-effective than glycemic control or lipid control at all ages, and across a wide ranging sensitivity analysis.

This is not to say that glycemic control is unimportant. When an individual patient has HbA1c >=1.5% above upper limit of normal, it is the duty of the physician to improve HbA1c, as well as to optimize blood pressure control, lipid control, tobacco control, and aspirin use. However, on a population level, it is important to emphasize diabetes quality improvement goals that maximize the health of the entire diabetes population, especially when they also maximize cost-effectiveness. In many populations, the time has come to place greater emphasis on blood pressure control, along with glycemic control, as a means to reduce mortality, morbidity, and costs attributable to diabetes mellitus.

Although I have argued for the precedence of blood pressure control over glycemic control as an appropriate focus for diabetes care improvement in some settings, a more unified approach to setting quality improvement goals might also be considered. In such an approach, several measures that meet the criteria listed in Figure 1 could be combined into a comprehensive measure of diabetes care quality. For example, a comprehensive quality measure may include in the denominator all adults with diabetes, and in the numerator those who are in the denominator who simultaneously meet a defined set of quality measures. These could include such things as HbA1c within 1.5% of normal, systolic blood pressure <130 mm Hg, and LDL cholesterol <100 mg/dl. Even in care settings with excellent levels of HbA1c, it is typical that <20% of those with diabetes currently satisfy this comprehensive measure. It is difficult to significantly improve such comprehensive measures without making fundamental changes in how chronic disease care is organized and delivered. Thus, adoption of these challenging measures may stimulate investments in office systems that can better support chronic disease (and preventive) care.



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  		Figure 1 Evidence-based criteria for the selection of quality improvement measures (improvement measures should meet all four criteria).

 
In summary, et al. should be congratulated for successfully achieving impressive levels of glycemic control in a defined population, and for presenting us with useful information that suggests the need for a systematic, evidence-based approach to selection of quality improvement goals. It is not surprising that our approach to quality improvement must evolve as the scientific basis of diabetes care changes and patterns of care in the community improve. Diabetes is increasingly recognized as an essentially vascular disease, and a principal objective of diabetes care is heart attacks and stroke prevention. In this context, blood pressure control, lipid control, tobacco control, and aspirin use deserve increased attention and focus, especially in patient populations with reasonably good glycemic control.

References

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