title: Comparative Assessment of Medical Resource Use and Costs Associated with Patients with Symptomatic Peripheral Artery Disease in the United States.
abstract: BACKGROUND
  There is growing concern about appropriate disease management for peripheral artery disease (PAD) because of the rapidly expanding population at risk for PAD and the high burden of illness associated with symptomatic PAD. A better understanding of the potential economic impact of symptomatic PAD relative to a matched control population may help improve care management for these patients.
  
  
  OBJECTIVE
  To compare the medical resource utilization, costs, and medication use for patients with symptomatic PAD relative to a matched control population.
  
  
  METHODS
  In this retrospective longitudinal analysis, the index date was the earliest date of a symptomatic PAD record (symptomatic PAD cohort) or any medical record (control cohort), and a period of 1 year pre-index and 3 years post-index was the study time frame. Symptomatic PAD patients and control patients (aged ≥ 18 years) enrolled in the MarketScan Commercial and Encounters database from January 1, 2006, to June 30, 2010, were identified. Symptomatic PAD was defined as having evidence of intermittent claudication (IC) and/or acute critical limb ischemia requiring medical intervention. Symptomatic PAD patients were selected using an algorithm comprising a combination of PAD-related ICD-9-CM diagnostic and diagnosis-related group codes, peripheral revascularization CPT-4 procedure codes, and IC medication National Drug Code numbers. Patients with stroke/transient ischemic attack, bleeding complications, or contraindications to antiplatelet therapy were excluded from the symptomatic PAD group but not the control group. A final 1:1 symptomatic PAD to control population with an exact match based on age, sex, index year, and Charlson Comorbidity Index (CCI) was identified. Descriptive statistics comparing patient demographics, comorbidities, medical resource utilization, cost, and medication use outcomes were generated. Generalized linear models were developed to compare the outcomes while controlling for residual difference in demographics, comorbidities, pre-index resource use, and pre-index costs.
  
  
  RESULTS
  3,965 symptomatic PAD and 3,965 control patients were matched. In both cohorts, 54.7% were male, with a mean age (SD) of 69.0 (12.9) years and a CCI score of 1.3 (0.9). Symptomatic PAD patients had more cardiovascular comorbidities than control patients (27.7% vs. 12.6% coronary artery disease, 27.1% vs. 15.9% hyperlipidemia, and 49.8% vs. 28.2% hypertension) in the pre-index period. Post-index rates of ischemic stroke, non-ST segment elevation myocardial infarction, unstable angina, and cardiovascular- or PAD-related procedures (limb amputations, endovascular procedures, open surgical procedures, percutaneous coronary intervention, and coronary artery bypass graft) were higher among symptomatic PAD patients versus control patients. All-cause annualized inpatient admissions (0.46 vs. 0.22 admissions), emergency department/urgent care days (0.27 vs. 0.22 days), and office visit days (12.5 vs. 10.2 days) were higher among symptomatic PAD versus control patients post-index. Annualized all-cause inpatient costs ($8,494 vs. $3,778); outpatient costs ($8,459 vs. $5,692); and total costs ($20,880 vs. $12,501) were higher among symptomatic PAD versus control patients post-index. Only 17.8% of symptomatic PAD patients versus 6.6% of control patients were on clopidogrel pre-index. In the post-index period, clopidogrel prescriptions in the symptomatic PAD population increased to 38.0%. Results were consistent in the regression models with the symptomatic PAD population having a higher number of all-cause post-index inpatient admissions, emergency department/urgent care days, office visit days, inpatient costs, outpatient costs, and total costs versus control patients (P ≤ 0.026).
  
  
  CONCLUSIONS
  Symptomatic PAD patients have significantly higher medical resource use and costs when compared with a matched control population. As the prevalence of symptomatic PAD increases, there will be a significant impact on the population and health care system. The rates of use of evidence-based secondary prevention therapies, such as antiplatelet medication, were low. Therefore, greater effort must be made to increase utilization rates of appropriate treatments to determine if the negative economic and clinical impacts of symptomatic PAD can be minimized.
  
  
  BACKGROUND
  This study was funded by Merck & Co., Kenilworth, New Jersey. Chase and Heithoff are employees of Merck & Co., Kenilworth, New Jersey, and Upper Gwynedd, Pennsylvania. Friedman and Navaratnam are paid consultants for Merck & Co. Simpson is a paid consultant for Merck, Pfizer, and Amgen and has received speaker's fees from Merck and Pfizer. Study concept and design were contributed by Chase, Navaratnam, and Heilhoff, along with Simpson and Friedman. Friedman collected the data, which was interpreted by Simpson and Navaratnam, along with Friedman. The manuscript was written by Navaratnam and Friedman, along with Chase, Heilhoff and Simpson, and revised by all of the authors.
authors.affiliation: 1 Merck & Co., Kenilworth, New Jersey.
authors.forename: Monica Reed
authors.initials: MR
authors.lastname: Chase
authors.affiliation: 2 DataMed Solutions, New York, New York.
authors.forename: Howard S
authors.initials: HS
authors.lastname: Friedman
authors.affiliation: 2 DataMed Solutions, New York, New York.
authors.forename: Prakash
authors.initials: P
authors.lastname: Navaratnam
authors.affiliation: 1 Merck & Co., Kenilworth, New Jersey.
authors.forename: Kim
authors.initials: K
authors.lastname: Heithoff
authors.affiliation: 3 University of North Carolina School of Medicine, Chapel Hill.
authors.forename: Ross J
authors.initials: RJ
authors.lastname: Simpson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D057186:Comparative Effectiveness Research / Q000191:economics* / Q000379:methods; D003362:Cost-Benefit Analysis / Q000191:economics / Q000379:methods; D005260:Female; D006295:Health Resources / Q000191:economics* / Q000706:statistics & numerical data*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D058729:Peripheral Arterial Disease / Q000191:economics* / Q000453:epidemiology / Q000628:therapy*; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology