title: The Danish National Lymphoma Registry: Coverage and Data Quality.
abstract: BACKGROUND
  The Danish National Lymphoma Register (LYFO) prospectively includes information on all lymphoma patients newly diagnosed at hematology departments in Denmark. The validity of the clinical information in the LYFO has never been systematically assessed.
  
  
  OBJECTIVE
  To test the coverage and data quality of the LYFO.
  
  
  METHODS
  The coverage was tested by merging data of the LYFO with the Danish Cancer Register and the Danish National Patient Register, respectively. The validity of the LYFO was assessed by crosschecking with information from medical records in subgroups of patients. A random sample of 3% (N = 364) was made from all patients in the LYFO. In addition, four subtypes of lymphomas were validated: CNS lymphomas, diffuse large B-cell lymphomas, peripheral T-cell lymphomas, and Hodgkin lymphomas. A total of 1,706 patients from the period 2000-2012 were included. The positive predictive values (PPVs) and completeness of selected variables were calculated for each subgroup and for the entire cohort of patients.
  
  
  RESULTS
  The comparison of data from the LYFO with the Danish Cancer Register and the Danish National Patient Register revealed a high coverage. In addition, the data quality was good with high PPVs (87% to 100%), and high completeness (92% to 100%).
  
  
  CONCLUSIONS
  The LYFO is a unique, nationwide clinical database characterized by high validity, good coverage and prospective data entry. It represents a valuable resource for future lymphoma research.
authors.affiliation: Department of Hematology, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Bente
authors.initials: B
authors.lastname: Arboe
authors.affiliation: Department of Hematology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Tarec Christoffer
authors.initials: TC
authors.lastname: El-Galaly
authors.affiliation: Department of Hematology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Michael Roost
authors.initials: MR
authors.lastname: Clausen
authors.affiliation: Department of Hematology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Peter Svenssen
authors.initials: PS
authors.lastname: Munksgaard
authors.affiliation: Department of Hematology, Copenhagen University Hospital, Herlev, Denmark.
authors.forename: Danny
authors.initials: D
authors.lastname: Stoltenberg
authors.affiliation: Department of Hematology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Mette Kathrine
authors.initials: MK
authors.lastname: Nygaard
authors.affiliation: Department of Hematology, Copenhagen University Hospital, Herlev, Denmark.
authors.forename: Tobias Wirenfeldt
authors.initials: TW
authors.lastname: Klausen
authors.affiliation: Department of Hematology, Odense University Hospital, Odense, Denmark.
authors.forename: Jacob Haaber
authors.initials: JH
authors.lastname: Christensen
authors.affiliation: Department of Hematology, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Jette Sønderskov
authors.initials: JS
authors.lastname: Gørløv
authors.affiliation: Department of Hematology, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Peter de Nully
authors.initials: Pde N
authors.lastname: Brown
mesh_terms: D000068598:Data Accuracy; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008223:Lymphoma / Q000453:epidemiology*; D008297:Male; D011159:Population Surveillance; D012042:Registries / Q000592:standards / Q000706:statistics & numerical data*