title: A practical method of linking data from Medicare claims and a comprehensive electronic medical records system.
abstract: BACKGROUND
  Linking administrative and clinical databases provides opportunities for richer studies to improve healthcare, but linkage may require sophisticated algorithms. Linking US Medicare data with large databases used for everyday clinical practice is seldom described in detail in medical literature.
  
  
  OBJECTIVE
  Test a deterministic method of linking data from a local electronic medical records system to Medicare data, and report specific details of the algorithm used as well as lessons learned from the linkage process.
  
  
  METHODS
  Medicare beneficiaries with medical encounters in selected Indiana counties in the 5-year period ending in 1999.
  
  
  RESULTS
  For 6,388 beneficiaries with Medicare data indicating inpatient encounters in the system, 98% had links to the clinical database. Of 7,231 patients hospitalized and registered in the local clinical system, 86% contained a link to Medicare data, and 69% contained a link even without using Social security number (SSN) as an identifier. Medicare data that conflicted with local hospital records by indicating no local hospitalization occurred in 1.8%. More than 2,000 claims contained hospital identifiers that did not exist in the hospital codebook.
  
  
  CONCLUSIONS
  Details of a practical, deterministic method of linking Medicare claims to a large electronic records system have been applied and described. Most records were linked without SSN. A variety of inconsistencies were found and these, along with missing or incomplete data, can influence linking. Integrity of specific variables must be assessed carefully.
authors.affiliation: Indiana University Center for Aging Research, Regenstrief Health Center, 1050 Wishard Blvd., 6th fl, Indianapolis, IN 46202-2872, USA. mw@cogit.net
authors.forename: Michael
authors.initials: M
authors.lastname: Weiner
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Stump
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Callahan
authors.forename: John N
authors.initials: JN
authors.lastname: Lewis
authors.forename: Clement J
authors.initials: CJ
authors.lastname: McDonald
mesh_terms: D000368:Aged; D003625:Data Collection; D016208:Databases, Factual; D006751:Hospital Information Systems; D006801:Humans; D016247:Information Storage and Retrieval; D007345:Insurance Claim Review / Q000706:statistics & numerical data*; D016347:Medical Records Systems, Computerized / Q000706:statistics & numerical data*; D006278:Medicare / Q000706:statistics & numerical data*