title: Data quality in the Danish National Acute Leukemia Registry: a hematological data resource.
abstract: BACKGROUND
  The Danish National Acute Leukemia Registry (DNLR) has documented coverage of above 98.5%. Less is known about the quality of the recorded data.
  
  
  OBJECTIVE
  To describe the present coverage of the DNLR, its completeness, and accuracy of individual variables for acute myeloid leukemia (AML). Furthermore, as a second measure of true coverage of the DNLR, to estimate AML incidence in Denmark from DNLR data and compare it to incidence reported from other AML registries.
  
  
  METHODS
  By the end of December 2011, the DNLR (established January 2000) included detailed data on a large, well-defined, and nonselected Danish population of 2,665 AML patients. We estimated positive predictive values (PPVs) and completeness for 30 variables, which included patient and disease characteristics, treatment, and treatment outcomes. We identified 260 AML patients (10% of all AML patients recorded in the DNLR). We used information from medical records as the gold standard.
  
  
  RESULTS
  Using the Danish National Registry of Patients as a reference, the coverage of the DNLR was 99.6%. The PPVs of the individual variables ranged from 89.4% to 100%. The completeness of individual variables varied between 60.7% and 100%. Stratification by time of registration in the DNLR (before 2006 versus 2006 and later) revealed higher PPVs and lower frequencies of missing data from 2006. Sex-adjusted incidence rates were 6.2/100,000 person-years (95% confidence interval 5.8-6.6) in males and 4.9/100,000 person-years (95% confidence interval 4.5-5.4) in females. Yearly incidence rates of AML were higher than the incidence rates reported from Sweden (4.5 and 4.2/100,000) and the US (4.5 and 3.1/100,000 in Caucasians).
  
  
  CONCLUSIONS
  With few exceptions, there were high values for PPVs and completeness of recorded data. Data accuracy and completeness have improved since the registry was established. The estimated incidence may indicate that the DNLR truly is more complete than other registries. In conclusion, the DNLR is a valuable resource for clinical research of AML.
authors.affiliation: Department of Hematology, Aarhus University Hospital, Aarhus, Denmark ; Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Lene Sofie Granfeldt
authors.initials: LS
authors.lastname: Ostgård
authors.forename: Jan Maxwell
authors.initials: JM
authors.lastname: Nørgaard
authors.forename: Marianne Tang
authors.initials: MT
authors.lastname: Severinsen
authors.forename: Henrik
authors.initials: H
authors.lastname: Sengeløv
authors.forename: Lone
authors.initials: L
authors.lastname: Friis
authors.forename: Morten Krogh
authors.initials: MK
authors.lastname: Jensen
authors.forename: Ove Juul
authors.initials: OJ
authors.lastname: Nielsen
authors.forename: Mette
authors.initials: M
authors.lastname: Nørgaard
keywords: acute myeloid leukemia; incidence; registration completeness; validation studies
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