title: Validity of International Classification of Diseases, Ninth Revision, Clinical Modification codes for estimating the prevalence of venous ulcer.
abstract: BACKGROUND
  The American Venous Forum issued a call to reduce the prevalence of venous ulcers (VUs) by 50% in 10 years. The objectives of this study were to determine the validity of the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes for VU and to estimate the prevalence of VU in a well-defined geographic population (Olmsted County, Minn).
  
  
  METHODS
  Rochester Epidemiology Project resources and 18 VU ICD-9-CM codes were used to identify residents with possible VUs during the 2-year period 2010-2011 (n = 1551). The complete medical records in the community were reviewed for a 15% random sample (n = 227) of these residents, and on the basis of prespecified criteria, patients were categorized as a VU or non-VU case. Continuous and categorical variables were compared between groups by the two-sample t-test and χ(2) test.
  
  
  RESULTS
  Ninety-three patients (41%) had active or healed VUs, 83 had non-VUs, and 51 never had ulcers but had stasis skin changes or skin infection. ICD-9-CM code 454.0 best identified VU cases (sensitivity, 24%; specificity, 100%). VU patients were older and heavier and more frequently had bilateral ulcers. On the basis of the random sample review, an estimated 635 patients had healed or active VUs during the 2-year period of the study. The prevalence of VUs in the Olmsted County population was estimated to be 210 per 100,000 person-years, with VU incidence (newly diagnosed ulcers) of 85 per 100,000 person-years.
  
  
  CONCLUSIONS
  ICD-9-CM VU codes operated poorly for VU identification. VU surveillance for estimating trends in incidence and prevalence of VUs will require better methods. The estimated prevalence of VUs in Olmsted County is 210 per 100,000 person-years. New ulcers developed each year in 85 of 100,000 people, an incidence that seems to be higher than in the previous epidemiologic study in this population.
authors.affiliation: Gonda Vascular Center, Mayo Clinic, Rochester, Minn. Electronic address: gloviczki.monika@gmail.com.
authors.forename: Monika L
authors.initials: ML
authors.lastname: Gloviczki
authors.affiliation: Gonda Vascular Center, Mayo Clinic, Rochester, Minn.
authors.forename: Henna
authors.initials: H
authors.lastname: Kalsi
authors.affiliation: Gonda Vascular Center, Mayo Clinic, Rochester, Minn.
authors.forename: Peter
authors.initials: P
authors.lastname: Gloviczki
authors.affiliation: Gonda Vascular Center, Mayo Clinic, Rochester, Minn.
authors.forename: Matthew
authors.initials: M
authors.lastname: Gibson
authors.affiliation: Department of Health Science Research, Mayo Clinic, Rochester, Minn.
authors.forename: Stephen
authors.initials: S
authors.lastname: Cha
authors.affiliation: Gonda Vascular Center, Mayo Clinic, Rochester, Minn; Department of Health Science Research, Mayo Clinic, Rochester, Minn.
authors.forename: John A
authors.initials: JA
authors.lastname: Heit