title: Validity of Peripheral Arterial Disease Diagnoses in the Danish National Patient Registry.
abstract: OBJECTIVE
  The objective was to validate the diagnoses of peripheral arterial disease (PAD) in the legs, obtained from national registers in Denmark.
  
  
  METHODS
  In total, 1435 registered cases of PAD were identified in the Danish National Patient Registry among 57,053 middle aged participants from the Danish Diet, Cancer and Health cohort study. Validation was performed by reviewing all medical records using pre-specified criteria for a diagnosis of PAD.
  
  
  RESULTS
  The overall positive predictive value (PPV) of PAD diagnoses was 69.4% [95% confidence interval (CI) 67.0-71.7]. The PPV of diagnoses given in departments of vascular surgery was significantly higher than diagnoses given in other departments: 71.9% (95% CI 69.2-74.4) versus 58.3% (95% CI 52.2-64.2), respectively. In a sub-study, 141 potential cases of PAD also registered in the Danish National Vascular Registry were evaluated, and a PPV of 87.9% (95% CI 81.4-92.4) was found for these diagnoses.
  
  
  CONCLUSIONS
  More than 30% of the diagnoses of PAD notified in the Danish National Patient Registry were not valid, stressing the importance of validation when using register information for research purposes. In contrast, diagnoses obtained from the Danish National Vascular Registry had a high validity ready for use without further validation.
authors.affiliation: Department of Vascular Surgery, Aalborg University Hospital, Aalborg, Denmark. Electronic address: a.lasota@rn.dk.
authors.forename: A N
authors.initials: AN
authors.lastname: Lasota
authors.affiliation: Department of Cardiology, Aalborg University Hospital, Aalborg, Denmark; Department of Public Health, Section for Epidemiology, Aarhus University, Aarhus, Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Overvad
authors.affiliation: Unit of Clinical Biostatistics and Bioinformatics, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: H H
authors.initials: HH
authors.lastname: Eriksen
authors.affiliation: UNIT of Diet, Genes and Environment, Danish Cancer Society Research Centre, Copenhagen, Denmark.
authors.forename: A
authors.initials: A
authors.lastname: Tjønneland
authors.affiliation: Department of Cardiology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: E B
authors.initials: EB
authors.lastname: Schmidt
authors.affiliation: Faculty of Medicine, Aalborg University, Aalborg, Denmark.
authors.forename: M-L M
authors.initials: MM
authors.lastname: Grønholdt
mesh_terms: D000368:Aged; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058729:Peripheral Arterial Disease / Q000175:diagnosis* / Q000453:epidemiology; D011237:Predictive Value of Tests; D012042:Registries; D015203:Reproducibility of Results
keywords: Danish National Patient Registry (NPR); Peripheral arterial disease (PAD); Validation study