title: Data quality at the Icelandic Cancer Registry: comparability, validity, timeliness and completeness.
abstract: BACKGROUND
  The nationwide Icelandic Cancer Registry (ICR) was established in 1954 and has been extensively used for research from the outset although formal quality assessment of the registry database has not previously been undertaken. In this paper we report the first formal evaluation of the comparability, validity, timeliness and completeness of the ICR.
  
  
  METHODS
  Data from the ICR for the period 1955-2009 (41 994 cancer diagnoses) were used, applying established quantitative and semi-quantitative methods. In order to evaluate the completeness of the ICR, record linkage was performed between the ICR and the population-based Hospital Discharge Registry to identify potential missing cases for tumour diagnoses in 2000 and 2001.
  
  
  RESULTS
  The registration is in accordance with internationally accepted standards. It has high validity, but random variation in rates is prominent in this small population. Record linkage with the Hospital Discharge Registry revealed that in addition to the 2459 cancers registered in 2000-2001, 21 cases were missing, indicating 99.15% completeness. Tumours of the central nervous system constituted 71%, and haematological malignancies 19% of these missing entries.
  
  
  CONCLUSIONS
  The ICR has high completeness, validity and timeliness and is comparable to the cancer registries of the other Nordic Countries. As cancer registries have many important roles, it is of great importance that their data are at all times as complete and valid as possible. Thus the ICR aims to constantly improve and update the data gathering process.
authors.affiliation: Icelandic Cancer Registry, Icelandic Cancer Society, Reykjavik, Iceland.
authors.forename: Lara Gudrun
authors.initials: LG
authors.lastname: Sigurdardottir
authors.forename: Jon Gunnlaugur
authors.initials: JG
authors.lastname: Jonasson
authors.forename: Sigrun
authors.initials: S
authors.lastname: Stefansdottir
authors.forename: Anna
authors.initials: A
authors.lastname: Jonsdottir
authors.forename: Gudridur Helga
authors.initials: GH
authors.lastname: Olafsdottir
authors.forename: Elinborg Jona
authors.initials: EJ
authors.lastname: Olafsdottir
authors.forename: Laufey
authors.initials: L
authors.lastname: Tryggvadottir
mesh_terms: D017677:Age Distribution; D002965:Classification / Q000379:methods; D003644:Death Certificates; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D015994:Incidence; D008297:Male; D009369:Neoplasms / Q000145:classification / Q000453:epidemiology* / Q000401:mortality; D009382:Neoplasms, Unknown Primary / Q000453:epidemiology; D012042:Registries / Q000592:standards*; D015203:Reproducibility of Results; D012107:Research Design; D017678:Sex Distribution; D013997:Time Factors