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J Am Med Inform Assoc 19:e157-e161 doi:10.1136/amiajnl-2011-000329
  • Research and applications
  • FOCUS on clinical research informatics

A simple heuristic for blindfolded record linkage

  1. Todd Ferris
  1. Center for Clinical Informatics, Stanford University, Stanford, California, USA
  1. Correspondence to Dr Susan C Weber, Stanford Center for Clinical Informatics, MSOB x200, 251 Campus Drive, Stanford, CA 94305, USA; scweber{at}stanford.edu
  • Received 25 April 2011
  • Accepted 2 January 2012
  • Published Online First 1 February 2012

Abstract

Objectives To address the challenge of balancing privacy with the need to create cross-site research registry records on individual patients, while matching the data for a given patient as he or she moves between participating sites. To evaluate the strategy of generating anonymous identifiers based on real identifiers in such a way that the chances of a shared patient being accurately identified were maximized, and the chances of incorrectly joining two records belonging to different people were minimized.

Methods Our hypothesis was that most variation in names occurs after the first two letters, and that date of birth is highly reliable, so a single match variable consisting of a hashed string built from the first two letters of the patient's first and last names plus their date of birth would have the desired characteristics. We compared and contrasted the match algorithm characteristics (rate of false positive v. rate of false negative) for our chosen variable against both Social Security Numbers and full names.

Results In a data set of 19 000 records, a derived match variable consisting of a 2-character prefix from both first and last names combined with date of birth has a 97% sensitivity; by contrast, an anonymized identifier based on the patient's full names and date of birth has a sensitivity of only 87% and SSN has sensitivity 86%.

Conclusion The approach we describe is most useful in situations where privacy policies preclude the full exchange of the identifiers required by more sophisticated and sensitive linkage algorithms. For data sets of sufficiently high quality this effective approach, while producing a lower rate of matching than more complex algorithms, has the merit of being easy to explain to institutional review boards, adheres to the minimum necessary rule of the HIPAA privacy rule, and is faster and less cumbersome to implement than a full probabilistic linkage.

Footnotes

  • Funding This work was funded in part by a grant from the Richard Levy Gift Fund, and in part by the Stanford NIH/NCRR CTSA award number UL1 RR025744. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Research Resources or the National Institutes of Health.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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