Prevalence, Incidence, and Outcomes of Critical Limb Ischemia in the US Medicare Population
- Volume 10 - Issue 2 - February 2013
- Posted on: 2/8/13
- 0 Comments
- 8104 reads
Onur Baser, MS, PhD,1 Patrice Verpillat,2 Sylvie Gabriel,2 Li Wang3
From 1STATinMED Research/The University of Michigan, Ann Arbor, Michigan, USA, 2Market Access and Pricing Strategy Department, Sanofi Groupe, Paris, France, and 3STATinMED Research, Dallas, Texas, USA.
ABSTRACT: Objective. This study aimed to assess annual prevalence and incidence of critical limb ischemia (CLI) and associated outcomes (amputation, leg revascularization, death) in elderly persons in the United States. Method. Medicare beneficiaries ages 65 and older were retrospectively analyzed and compared for demographic and clinical characteristics from January 2007 to December 2008. Using the direct standardization method, year, age, gender, and race, as well as diabetes-specific prevalence and incidence rates were estimated for the CLI burden in the United States. Potential risk factors for CLI outcomes, events, and mortality were selected using Cox proportional hazard regression models. CLI prevalence and incidence was 0.23% and 0.20% respectively. Similar to prevalence, incidence increased sharply among beneficiaries ages 65 to 69 (0.13%) to 85 and older (0.31%). Results. Among black patients, 0.41% had CLI, compared to 0.18% among white patients. Diabetes caused 7.6 times increased CLI risk compared to nondiabetic patients. In the multivariate analysis, younger, male, diabetic (HR 1.21), or proliferative retinopathy (HR 1.112) patients were significantly associated with nontraumatic amputation, while hypertension (HR 1.043), angina pectoris (HR 1.074), myocardial infarction (HR 1.08), or hyperlipidemia (HR 1.1) were significantly related to leg revascularization. Black patients had a lower revascularization probability and a higher amputation probability than white patients (after adjustment for age, gender, CLI severity, comorbidities), and displayed a longer time to first revascularization and shorter time to amputation. Older, male and black patients had higher CLI prevalence. Conclusion. CLI management differs among the US population according to ethnicity, leading to varying outcomes (revascularization, amputation). Since outcome event risk varies, patients should be examined individually.
VASCULAR DISEASE MANAGEMENT 2013:10(2):E26-E36
Key words: critical limb ischemia, prevalence, incidence, revascularization, amputation
Critical limb ischemia (CLI) is a severe obstruction of the arteries that seriously decreases blood flow to the extremities.1 Although the hallmark of peripheral arterial occlusive disease is an inadequate blood flow to supply vital oxygen demanded by the limb, CLI occurs after a chronic lack of blood supply resulting in a cascade of pathophysiologic events that ultimately leads to severe pain in the feet or toes, even while resting,2 and at a later stage sores and wounds that will not heal on the legs and feet. Thus, these patients would be classified as stage III or IV in the Fontaine classification, given that CLI is considered the “end stage” of peripheral arterial disease (PAD).3,4 If left untreated, CLI will lead to amputation of the affected limb.5
Although CLI continues to be a significantly morbid disease process for the aging population, the epidemiology of CLI remains sparse in the US population. To date, the number of US patients suffering from CLI has been estimated indirectly, from the estimated number of amputations,6 CLI incidence in the United Kingdom and Ireland based on a 1995 survey of vascular surgeons,7,8 estimated progression from intermittent claudication (IC) or a combination of amputations, revascularizations, and progression from IC in Italy.9
The estimations from these indirect calculations vary widely. Although CLI incidence of 300 per million per year has been calculated by Weitz et al, who estimated that 1% of Americans over age 50 years may ultimately acquire chronic CLI,10 Goodney et al. claims that diagnosed CLI currently affects roughly 1 million Americans.11 Recently published analysis by The Sage Group concluded that an estimated 2 million people in the United States have CLI, including undiagnosed patients.12 Reflecting the aging population, this number is projected to grow to almost 2.8 million by 2020. However, if the prevalence of diabetes continues to increase, there could be over 3.5 million cases of CLI by 2020.12
Prompt medical care is crucial in all patients with CLI to immediately improve blood flow and prevent nontraumatic lower-extremity amputation (LEA). LEA is often an expensive and catastrophic complication leading to permanent disability and a reduction in functional status, which thereby decreases quality of life.13 The Centers for Disease Control and Prevention reported in 1997 that, in the United States, the LEA rate among those with diabetes was 28 times that of those without diabetes.14 In another report by Bertele et al15 in 1999, a 6-month amputation rate of 12% and a 1-year mortality rate of 19.1% were observed in CLI patients. In a study of Medicare patients who underwent lower extremity amputation from 2003 to 2006, variation was evident in the intensity of vascular care given before amputation, which was likely due to regional practice patterns.11 Up to 80% of patients in various regions throughout the United States received a vascular procedure within 1 year of amputation, and less than 12% of patients in other regions underwent a vascular procedure 1 year before amputation.