title: Data completeness can be optimized in clinical databases.
abstract: BACKGROUND
  The aim of the present paper was to analyse the incidence of and reasons for data incompleteness in reporting of colorectal cancer from a single department to a national database.
  
  
  METHODS
  A list of errors comparing the database with the National Patient Registry is drawn up monthly and has been used for data completeness analysis for several years as part of the department's daily routine. In May 2009, this system was revised and we identified a number of new errors which we previously thought had been corrected. The nature of these errors has been analysed in detail.
  
  
  RESULTS
  According to the National Patients Registry, a total of 1,530 patients were treated for a first-time colorectal cancer. In 60 cases (3.9%) patients were missing in the database. Erroneous registration of the diagnosis in the National Patient Registry on the part of the department was the primary reason why data were missing. This was followed by clerical errors at the department. All mistakes were explainable, but changes in the registry structure prevented some of the mistakes discovered from being corrected retrospectively.
  
  
  CONCLUSIONS
  The number of missing patients in the database could be minimized by a meticulous effort at controlling data and comparing them with data in national registries.
authors.affiliation: Department of Surgery K, Bispebjerg Hospital, Faculty of Health Sciences, University of Copenhagen, Denmark. pwil0002@bbh.regionh.dk
authors.forename: Peer
authors.initials: P
authors.lastname: Wille-Jørgensen
mesh_terms: D015179:Colorectal Neoplasms; D003627:Data Interpretation, Statistical; D016208:Databases, Factual / Q000592:standards* / Q000706:statistics & numerical data; D003718:Denmark; D006801:Humans; D015994:Incidence; D012042:Registries / Q000592:standards* / Q000706:statistics & numerical data; D012107:Research Design