Improving Treatment Success Rates for Type 2 Diabetes: Recommendations for a Changing Environment

Abstract

As demonstrated by suboptimal levels of therapeutic goal achievement, there exists significant room for improvement in type 2 diabetes management. Despite widespread disease awareness and high rates of risk-factor testing in managed care, effective metabolic control in patients with type 2 diabetes is lacking and points toward a phenomenon known as clinical inertia. Clinical inertia, defined as a failure to initiate or advance therapy in a patient who is not at the evidence-based goal, is a key contributing factor in the suboptimal rates of therapeutic target achievement for type 2 diabetes. The causes of clinical inertia are multifactorial and interactive, arising among patients, providers, and health systems and from specific characteristics of available treatments. Therapeutic nonadherence is perhaps the most significant factor contributing to clinical inertia, with recent analyses demonstrating that providers are more likely to prescribe a dose escalation in patients who are adherent to therapy compared with those who are not. While the concept may be counterintuitive, antihyperglycemic agents also have the potential to cause or contribute to the phenomenon of clinical inertia. This often occurs via factors inherent to the drugs themselves, such as treatment-related adverse effects (eg, hypoglycemia, weight gain, edema, gastrointestinal symptoms), perception of long-term safety profiles, and the complexity of the treatment regimen. Often not considered, but equally important, is the durability of an antihyperglycemic agent to maintain glycosylated hemoglobin (A1C) level goals. Because no monotherapy exists to arrest the pancreatic β-cell failure of type 2 diabetes, early combination therapy with thiazolidinediones and glucagon-like protein-1 agonists that is associated with sustained A1C level reduction is the only hope to change the progressive nature of type 2 diabetes mellitus.

(Am J Manag Care. 2010;16:S195-S200)

In the United States, most patients with type 2 diabetes fail to meet therapeutic goals. Recent estimates of the proportion of patients achieving the American Diabetes Association's (ADA's) glycosylated hemoglobin (A1C) goal of less than 7.0% range from 49.8% to 57.1%, and only 33.0% of patients achieve the American Association of Clinical Endocrinologists' more aggressive goal of less than 6.5%.^1-3 Similar results have been reported for goals related to blood pressure (BP <130/80 mmHg; 45.5%), low-density lipoprotein cholesterol (LDL-C <100 mg/dL; 45.6%), and an aggregate of A1C level, BP, and LDL-C (12.2%).³

The proportion of patients with type 2 diabetes meeting these therapeutic target measures has improved since 2002, but barriers to optimizing diabetes care in the United States still exist.³ In a retrospective cohort study, Grant et al analyzed data from 30 US academic medical centers to assess measurement and control of A1C level, BP, and cholesterol, as well as the corresponding medical regimen changes at the most recent clinic visit.⁴ Despite very high annual testing rates for the 3 therapeutic markers (97.4% for A1C level, 96.6% for BP, and 87.6% for total cholesterol), few patients achieved ADA-recommended goals (A1C level, 34.0%; BP, 33.0%; LDL-C, 46.1%; aggregate, 10.0%).⁴ Furthermore, at the most recent clinic visit, only 40.4% of patients with A1C concentrations above goal underwent adjustment of their corresponding regimens.⁴ Even among patients with elevated BP or LDL-C who were not receiving therapy for these conditions, the majority remained untreated (89.9% and 94.4%, respectively).⁴ These results underscore that high rates of risk-factor testing do not necessarily translate to effective metabolic control, and point toward a phenomenon known as clinical inertia as a contributing factor to the poor goal achievement in patients with type 2 diabetes.⁴

Clinical Inertia: Contributing Factors and Potential Solutions

Clinical inertia is defined as a failure to initiate or advance therapy in a patient who is not at the evidence-based goal. This phenomenon in healthcare is propagated by a number of multifactorial, interactive situations among patients, providers, and health systems, and by available treatment options. While specific scenarios or characteristics in any one of these areas may cause clinical inertia, it is more likely to be the result of several contributing factors that combine to stall or thwart the initiation or advancement of effective, evidence-based therapy.

Therapeutic nonadherence is perhaps the most significant factor contributing to clinical inertia. Among patients with type 2 diabetes, 10.5% fail to refill prescriptions for antidiabetic medications after the first fill and 37.0% discontinue therapy within 12 months of the initial prescription.⁵ According to a recent claims database analysis, providers are more likely to prescribe a dose escalation in patients who are adherent to therapy compared with those who are not, demonstrating the correlation between therapeutic adherence and clinical inertia.⁶ In doing so, providers tend to "reward" adherence and persistence by being more likely to advance or intensify therapy to effective levels in patients who take their antidiabetic medications as prescribed but are still not reaching ADA-recommended goals.

Despite the integral role that therapeutic nonadherence plays in determining the likelihood of clinical inertia, it should be noted that these phenomena also exist independent of each other. In one of the first studies to examine both medication adherence and treatment intensification rates in a single diabetes population, Schmittdiel et al reported no treatment intensification in 30% of patients with hyperglycemia who were above A1C level goal and had no evidence of poor adherence.⁷ These results indicate the existence of clinical inertia even among patients who are adherent to therapy.

Beyond therapeutic adherence, providers are also influenced by a number of other factors that contribute to clinical inertia. Delayed diagnosis and initiation of therapy can result in clinical inertia when physicians attribute elevated A1C levels to patient diet and lifestyle and do not actively treat the disease.⁶ In addition to therapeutic nonadherence, providers often assume that patients will not adhere to the treatment plan they really want to recommend, resulting in a reluctance to prescribe the appropriate intensity of therapy.⁶ Despite knowing evidence-based-recommended A1C goals, A1C levels above goal may be labeled as "good enough," further contributing to clinical inertia from the provider perspective.⁶ Exacerbating this is the common overestimation of personal guideline adherence among providers.⁶ In addition to all the factors that propagate clinical inertia on the part of providers, the movement toward patient-driven care in physician training influences thinking that is detrimental to overcoming this phenomenon. With this line of thinking, healthcare providers are taught to prioritize the patients' immediate concerns and comfort in therapeutic considerations. This trend leads providers to address only conditions that are symptomatic, or rather, those symptoms which cause patient complaint. This "one visit, one problem" philosophy can result in clinical inertia among providers, and ultimately in unaddressed and serious, asymptomatic chronic disease, despite clinical laboratory results or other pertinent data.⁸

In addition to the standard initiatives to improve therapeutic adherence among patients, a number of provider-directed strategies may be applied to address clinical inertia at the patient-provider level in managed care. Provider education initiatives create the foundation on which to base these strategies, and are rooted in the concept that type 2 diabetes, although asymptomatic, eventually culminates in significant morbidity and mortality. Also, education on updated pathophysiologic treatment of type 2 diabetes mellitus is imperative. Furthermore, providers need to be familiar with guideline recommendations and consensus therapeutic goals for the disease. Electronic medical records (EMRs) are an information technology (IT)-based initiative in which data prompts allow the computer system to notify providers whether a particular intervention is appropriate based on current lab work; however, EMR-prompt effectiveness is controversial. Other provider-directed interventions that may assist in overcoming clinical inertia include pay-for-performance initiatives, which use payment methods and other incentives to encourage quality improvement and patient-focused, high-value care. These initiatives, however, are relatively new in managed care, and further evaluation is needed to determine their full worth in the real-world setting.

Although certain components of the managed healthcare process may serve to propagate clinical inertia based on their inherent characteristics, success factors associated with health systems can reduce clinical inertia. First, the system should be designed to achieve and maintain evidence-based goals while preserving the cost-controlling tenets of managed care. For example, an appropriate tier structure for coverage of medications, such as value-based benefit design, can assist in maintaining access to therapies for chronic disease while continuing to manage utilization. Time and data issues contributing to clinical inertia can be overcome through the use of IT-based interventions that maximize efficiency and make the most of providers' time while supporting appropriate, evidence- based care. EMRs and clinical decision support tools (eg, algorithms, data prompts) are examples of such managed care initiatives. Finally, implementing and integrating a chronic care model can help managed care organizations minimize clinical inertia by providing a planwide appropriate strategy for treating chronic conditions. This approach is supported by cost savings generated through the prevention of disease-related complications and the cost-effectiveness of evidence-based treatments for type 2 diabetes.

While the concept may be counterintuitive, antihyperglycemic agents also have the potential to cause or contribute to the phenomenon of clinical inertia. This often occurs via factors inherent to the drugs themselves, such as treatment-related adverse effects (eg, hypoglycemia, weight gain, edema, gastrointestinal symptoms), perception of long-term safety profiles, and the complexity of the treatment regimen. Often not considered, but equally important, is the durability of an antihyperglycemic agent to maintain A1C goals. These considerations for traditional and novel antihyperglycemic medications will be subsequently reviewed.

Considerations for Antihyperglycemic Agents

Diabetes is a chronic disease, and the horizon for treating patients with diabetes is indefinite and continues for life. Therefore, the sustainability of A1C level reduction is a critical consideration for type 2 diabetes therapies. In addition, type 2 diabetes is a condition characterized by true endocrine organ failure, manifesting as progressive pancreatic β-cell failure. Unlike the failure associated with other organs, such as kidneys, the provider community may not fully understand the impact of arresting progressive β-cell dysfunction and its central role in the progression of type 2 diabetes mellitus. Pancreatic β-cell dysfunction begins well before a patient is diagnosed with type 2 diabetes; the most common diagnostic marker for diabetes, plasma glucose level, only becomes high enough for providers to intervene when there is 50% to 80% loss of β-cell function. Currently, no antihyperglycemic agents approved for the treatment of type 2 diabetes have proved to halt the progressive organ failure associated with the advanced stages of this disease. Some novel agents that have come to the market, however, may maintain or significantly slow β-cell function decline. Although β-cell function declines progressively for years prior to diagnosis, current treatment strategies fail to address this until plasma glucose levels significantly increase to current diagnostic levels.⁹ There is some logic behind this, as many patients with prediabetes may return to normal glucose tolerance without pharmacologic intervention. Unfortunately, currently defined and diagnosed diabetes may be treated too late to arrest this organ failure, and no antihyperglycemic monotherapy will stop β-cell decline (as evidenced by data based on durability of A1C level reduction).

Figure 1

Due to the progressive pancreatic β-cell failure characteristic of type 2 diabetes, patients' A1C concentrations slowly increase over time, regardless of which of the 3 most common antidiabetic agents is prescribed.10 Comparative studies in newly diagnosed patients with type 2 diabetes mellitus have demonstrated that thiazolidinediones (TZDs) are more effective than metformin or sulfonylureas at slowing this progression, yet no monotherapy is capable of fully arresting β-cell failure as measured by the decay of A1C level control over time.¹⁰ The sulfonylureas in particular tend to demonstrate a robust initial response in A1C level reduction, and thus can be used acutely for glucose control, but the initial response is followed by rapid deterioration of A1C level control over several years.^9,10 For this reason, clinician advocacy of the sulfonylureas is declining, and consensus recommendations are moving away from this class of antihyperglycemics. Sulfonylureas may also be contributing to clinical inertia, as a decline in treatment effect is often attributed to patients' diet and lifestyle adherence rather than poor durability in treatment effect. In contrast, metformin and the TZDs, namely rosiglitazone and pioglitazone, have demonstrated effective, sustained A1C level reductions over years ().^9,10

Figure 2

Figure 3

Another antihyperglycemic drug class that has demonstrated potential benefit in durability of A1C level reduction is the glucagon-like protein-1 (GLP-1) agonists.¹¹ In an open-label completers-only trial, the GLP-1 agonist exenatide demonstrated sustained A1C level reductions out to 3 years ().¹¹ Another relatively new class of antihyperglycemic agents, the dipeptidyl peptidase-4 (DPP-4) inhibitors, have demonstrated efficacy in reducing A1C concentration to optimal levels and are well tolerated; however, these agents do not appear to possess the sustainability for decreasing A1C levels. In a randomized, double-blind, 2-year study, addition of sitagliptin or glipizide to metformin background therapy produced no statistically different A1C levels, and both agents were associated with similar deteriorations in A1C level over time. When sitagliptin was combined with metformin over 2 years in an extension study, increases in A1C levels were similar ().^12-14

This difference in effect among the GLP-1 agonists and DPP-4 inhibitors is likely a function of their mechanisms of action. The DPP-4 inhibitors reduce degradation of endogenous GLP-1, hence increasing GLP-1 levels. Administration of the DPP-4 inhibitor sitagliptin doubled GLP-1 levels in a study by DeFronzo et al.¹⁵ However, this doubling effect results in only normal, nondiabetic physiologic GLP-1 plasma levels. In the same study, administration of exenatide, which has a potency similar to that of endogenous GLP-1, increased the plasma exenatide levels 4-fold, demonstrating pharmacologic levels of GLP-1 receptor agonism.¹⁵ This may account for the difference in sustained A1C level effects between the 2 classes of medication. Physiologic GLP-1 levels achieved by the administration of DPP-4 inhibitors have a weight-neutral effect with no gastric emptying, nausea, or vomiting. Conversely, the pharmacologic levels of GLP-1 achieved by GLP-1 agonists result in weight loss, slowing of gastric emptying, satiety, and more nausea and vomiting. Because both drug classes release insulin in a glucose-dependent manner, the risk of hypoglycemia is minimized as long as these agents are not combined with other agents that can produce hypoglycemia.

Similar results demonstrating the improved sustainability of A1C level reduction among GLP-1 agonists were reported at the 70th Annual Scientific Sessions of the American Diabetes Association.15 Patients treated with the GLP-1 agonist liraglutide in combination with metformin experienced greater sustained reductions in A1C levels at 52 weeks than those treated with sitagliptin (a DPP-4 inhibitor) plus metformin (-1.5% vs -0.9%).¹⁶ Greater weight loss was observed in patients treated with the liraglutide compared with sitagliptin (3.7 vs 1.2 kg).¹⁶

Table

Although combination therapy agents with durable A1C level reductions should be the mainstay in treating the chronic, progressive pathophysiology of type 2 diabetes, drug regimens should be tailored to each patient's clinical characteristics and therapeutic needs. The diverse array of antihyperglycemic agents warrant consideration based on their unique attributes, such as adverse-event profile and nonglycemic effects, in addition to durability of A1C level reduction. A brief synopsis of these agents, along with recommendations for their use in specific patient populations, is found in the .

Conclusions

Failure to achieve therapeutic targets in type 2 diabetes mellitus is multifactorial. Clinical inertia is the result of interrelated factors among patients, providers, and managed care organizations. In addition to these 3 key contributors to clinical inertia, a component often overlooked is the attributes of antihyperglycemic agents.

Antihyperglycemic agents drive clinical inertia as a result of their inherent characteristics, such as treatment-related adverse effects, perceptions related to their long-term safety, complexity of the treatment regimen, and durability of sustained A1C level reduction. Although further research is needed to assess the durability of sustained A1C level reduction with antihyperglycemic agents, it has the potential to be very influential in predicting the likelihood of clinical inertia. This is exemplified with the sulfonylureas, which produce robust and immediate, although unsustained, longterm reductions in A1C levels. This characteristic of the sulfonylurea class has led many diabetes experts to move away from the use of sulfonylureas in practice and to the gradual de-emphasis of these agents in some consensus treatment recommendations. Oral TZDs and novel GLP-1 agonists appear to have the most durable effects in terms of A1C level reduction, making these agents ideal for use in combination therapy. In addition, combination therapy has a low risk of hypoglycemia, and may offset some unwanted nonglycemic effects of the TZD class. Because no monotherapy exists to arrest the pancreatic β-cell failure of type 2 diabetes, early combination therapy with TZDs and GLP-1 agonist agents that feature sustained A1C level effects is the only hope of changing the progressive nature of type 2 diabetes mellitus, although long-term data are lacking.

Despite these forward-looking recommendations, an extensive armamentarium of antihyperglycemic agents is available to clinicians, and therapy should be tailored to the individual patient as indicated by their disease characteristics and therapeutic needs (Table). Pharmacotherapy should be targeted to patients based on the underlying pathophysiology, clinical characteristics, achievement of glycemic goals, drug side effects, durability of A1C level reduction, and nonglycemic effects.

Author Affiliations: Texas Diabetes Institute and the University of Texas Health Science Center at San Antonio, San Antonio, TX.

Funding Source: Financial support for this work was provided by Novo Nordisk.

Author Disclosure: Dr Triplitt reports receipt of lectureship fees and payment for involvement in the preparation of this manuscript from Novo Nordisk.

Authorship Information: Drafting of the manuscript; analysis and interpretation of data; and critical revision of the manuscript for important intellectual content.

Address correspondence to: Curtis Triplitt, PharmD, CDE, University of Texas Health Science Center at San Antonio, 701 S Zarzamora St, San Antonio, TX 78207. E-mail: curtis.triplitt@uhs-sa.com.

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