title: [Linkage of secondary data with cancer registry data on the basis of encrypted personal identifiers - results from a pilot study in North Rhine-Westphalia].
abstract: BACKGROUND
  The Cancer Registry of North-Rhine-Westphalia stores exclusively encrypted personal identifiers of registered cancer patients. Therefore, comparisons with secondary data sets can only be performed by record linkage procedures that are based on encrypted personal identifiers. We report on a pilot study which linked encrypted personal data from the disease management program for patients with diabetes mellitus type 2 (DMP-DM2) with the database of the EKR NRW in order to test the feasibility and efficiency of these record linkage procedures.
  
  
  METHODS
  Personal identifying variables of the DMP records were encrypted in a 2-stage process before being sent electronically to the EKR NRW where they were subsequently submitted to a probabilistic record linkage with the registry data. The study included 27 450 participants who were insured at the AOK NordWest, residents of the district Münster and who were aged 40-79 years at the time of first enrolment to the DMP-DM2 between June 2003-July 2008.
  
  
  RESULTS
  The electronic processing time of the semi-automatic record linkage procedure took about 24 h. Approximately 2% of the records had to be reviewed manually. After exclusion of prevalent cancer cases, multiple primaries and inadequate data, 26 742 participants (47.3% men; 52.7% women) remained in the data set. About 1 364 cohort members (759 men, 605 women) were diagnosed with cancer after submission to the disease management program.
  
  
  CONCLUSIONS
  The DMP-DM2 records were encrypted and linked to cancer registry data with a moderate personnel and financial input and high efficiency. Linked records were instantly usable for epidemiological analyses. Experiences of the pilot study suggest that future linkage studies can further advance the level of data protection, without losses in efficiency, by moderately complex software modifications and amendments of the data flow.
authors: Epidemiologisches Krebsregister Nordrhein-Westfalen gGmbH, Münster. hiltraud.kajueter@krebsregister.nrw.de
authors: H
authors: H
authors: Kajüter
authors: W U
authors: WU
authors: Batzler
authors: V
authors: V
authors: Krieg
authors: O
authors: O
authors: Heidinger
authors: H-W
authors: HW
authors: Hense
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D016494:Computer Security; D003219:Confidentiality; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D057286:Electronic Health Records / Q000706:statistics & numerical data*; D005260:Female; D005858:Germany / Q000453:epidemiology; D055991:Health Records, Personal; D006801:Humans; D008297:Male; D008498:Medical Record Linkage / Q000379:methods*; D008875:Middle Aged; D009369:Neoplasms / Q000453:epidemiology*; D010355:Patient Identification Systems / Q000706:statistics & numerical data*; D010865:Pilot Projects; D012042:Registries