title: Epidemiology of peripheral arterial disease and critical limb ischemia in an insured national population.
abstract: BACKGROUND
  Critical limb ischemia (CLI) represents the most severe clinical manifestation of peripheral arterial disease (PAD) and is the major cause of ischemic amputation in the United States. Risk factors and the associated incidence and prevalence of CLI have not been well described in the general population. This study describes the risk factors for PAD progression to CLI and estimates the annual incidence and prevalence of CLI in a representative United States patient cohort.
  
  
  METHODS
  This was a retrospective cohort analysis of adults with commercial, Medicare supplemental, or Medicaid health insurance who had at least one PAD or CLI health care claim from January 1, 2003, through December 31, 2008, and 12 months of continuous coverage. Two subgroups of CLI presentation were identified: primary CLI (patients without any prior PAD or subsequent PAD diagnostic code >30 days after CLI diagnostic code) and secondary CLI (patients with prior PAD or subsequent PAD diagnostic codes ≤30 days of a CLI diagnostic code). Patterns of presentation, annual incidence, and prevalence of CLI were stratified by health care plan. Risk factors for progression to CLI were compared by presentation type.
  
  
  RESULTS
  From 2003 to 2008, the mean annual incidence of PAD was 2.35% (95% confidence interval [CI], 2.34%-2.36%) and the incidence of CLI was 0.35% (95% CI, 0.34%-0.35%) of the eligible study population, with primary and secondary presentations occurring at similar rates. The mean annualized prevalence of PAD was 10.69% (95% CI, 10.67%10.70%) and the mean annualized prevalence of CLI was 1.33% (95% CI, 1.32%-1.34%) of the eligible study population, and two-thirds of the cases presented as secondary CLI. CLI developed in 11.08% (95% CI, 11.30%-11.13%) of patients with PAD. A multivariable model demonstrated that diabetes, heart failure, stroke, and renal failure were stronger predictors of primary rather than secondary CLI presentation.
  
  
  CONCLUSIONS
  These data establish new national estimates of the incidence and prevalence of CLI and define key risk factors that contribute to primary or secondary presentations of CLI within a very large contemporary insured population cohort in the United States.
authors.affiliation: Vascular Surgery Section, Department of Surgery, University of Colorado Denver, Aurora, Colo. Electronic address: mark.nehler@ucdenver.edu.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Nehler
authors.affiliation: Lillehei Clinical Research Unit, Cardiovascular Division, Department of Medicine, University of Minnesota Medical School, Minneapolis, Minn.
authors.forename: Sue
authors.initials: S
authors.lastname: Duval
authors.affiliation: Department of Medicine, CPC Clinical Research, Aurora, Colo.
authors.forename: Lihong
authors.initials: L
authors.lastname: Diao
authors.affiliation: Division of Cardiovascular Medicine, Department of Medicine, University of Virginia, Charlottesville, Va.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Annex
authors.affiliation: Division of Cardiology, Department of Medicine, University of Colorado School of Medicine, and Department of Medicine, CPC Clinical Research, Aurora, Colo.
authors.forename: William R
authors.initials: WR
authors.lastname: Hiatt
authors.affiliation: Division of Cardiology, Department of Medicine, University of Colorado School of Medicine, and Department of Medicine, CPC Clinical Research, Aurora, Colo.
authors.forename: Kevin
authors.initials: K
authors.lastname: Rogers
authors.affiliation: Lockheed Martin, Aurora, Colo.
authors.forename: Armen
authors.initials: A
authors.lastname: Zakharyan
authors.affiliation: Vascular Medicine Program, Lillehei Heart Institute and Cardiovascular Division, University of Minnesota Medical School, Minneapolis, Minn.
authors.forename: Alan T
authors.initials: AT
authors.lastname: Hirsch
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D016638:Critical Illness; D018450:Disease Progression; D005260:Female; D006333:Heart Failure / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007511:Ischemia / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008484:Medicaid; D006278:Medicare; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D058729:Peripheral Arterial Disease / Q000175:diagnosis / Q000453:epidemiology*; D015995:Prevalence; D051437:Renal Insufficiency / Q000453:epidemiology; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology; D013997:Time Factors; D014481:United States / Q000453:epidemiology