title: Design and implementation of a privacy preserving electronic health record linkage tool in Chicago.
abstract: OBJECTIVE
  To design and implement a tool that creates a secure, privacy preserving linkage of electronic health record (EHR) data across multiple sites in a large metropolitan area in the United States (Chicago, IL), for use in clinical research.
  
  
  METHODS
  The authors developed and distributed a software application that performs standardized data cleaning, preprocessing, and hashing of patient identifiers to remove all protected health information. The application creates seeded hash code combinations of patient identifiers using a Health Insurance Portability and Accountability Act compliant SHA-512 algorithm that minimizes re-identification risk. The authors subsequently linked individual records using a central honest broker with an algorithm that assigns weights to hash combinations in order to generate high specificity matches.
  
  
  RESULTS
  The software application successfully linked and de-duplicated 7 million records across 6 institutions, resulting in a cohort of 5 million unique records. Using a manually reconciled set of 11 292 patients as a gold standard, the software achieved a sensitivity of 96% and a specificity of 100%, with a majority of the missed matches accounted for by patients with both a missing social security number and last name change. Using 3 disease examples, it is demonstrated that the software can reduce duplication of patient records across sites by as much as 28%.
  
  
  CONCLUSIONS
  Software that standardizes the assignment of a unique seeded hash identifier merged through an agreed upon third-party honest broker can enable large-scale secure linkage of EHR data for epidemiologic and public health research. The software algorithm can improve future epidemiologic research by providing more comprehensive data given that patients may make use of multiple healthcare systems.
authors.affiliation: Department of Medicine, and Center for Health Information Partnerships, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA akho@nm.org.
authors.forename: Abel N
authors.initials: AN
authors.lastname: Kho
authors.affiliation: Department of Medicine, and Center for Health Information Partnerships, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA Department of Veterans Affairs, Pittsburgh PA.
authors.forename: John P
authors.initials: JP
authors.lastname: Cashy
authors.affiliation: Department of Medicine, and Center for Health Information Partnerships, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Jackson
authors.affiliation: Department of Medicine, and Center for Health Information Partnerships, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: Adam R
authors.initials: AR
authors.lastname: Pah
authors.affiliation: Department of Medicine, and Center for Health Information Partnerships, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: Satyender
authors.initials: S
authors.lastname: Goel
authors.affiliation: Department of Economics, University of Chicago, Chicago, IL, USA.
authors.forename: Jörn
authors.initials: J
authors.lastname: Boehnke
authors.affiliation: Department of Economics, University of Chicago, Chicago, IL, USA.
authors.forename: John Eric
authors.initials: JE
authors.lastname: Humphries
authors.affiliation: Society of Fellows Department of Economics, Business School, Program For Evolutionary Dynamics, and Center for Research on Computation and Society, Harvard University, Cambridge, MA, USA.
authors.forename: Scott Duke
authors.initials: SD
authors.lastname: Kominers
authors.affiliation: Department of Medicine, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Bala N
authors.initials: BN
authors.lastname: Hota
authors.affiliation: Department of Medicine, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Shannon A
authors.initials: SA
authors.lastname: Sims
authors.affiliation: Department of Biomedical Informatics, School of Medicine, and Department of Electrical Engineering and Computer Science, School of Engineering, Vanderbilt University, Nashville, TN, USA.
authors.forename: Bradley A
authors.initials: BA
authors.lastname: Malin
authors.affiliation: Center for Healthcare Studies and Department of Ophthalmology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Dustin D
authors.initials: DD
authors.lastname: French
authors.affiliation: Department of Medicine, and Center for Health Information Partnerships, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: Theresa L
authors.initials: TL
authors.lastname: Walunas
authors.affiliation: Department of Veterans Affairs, Pittsburgh PA.
authors.forename: David O
authors.initials: DO
authors.lastname: Meltzer
authors.affiliation: Alliance of Chicago Community Health Services, Chicago, IL, USA.
authors.forename: Erin O
authors.initials: EO
authors.lastname: Kaleba
authors.affiliation: Formerly of Chicago Department of Public Health, currently at Ann and Robert H. Lurie Children's Hospital, Chicago, IL, USA.
authors.forename: Roderick C
authors.initials: RC
authors.lastname: Jones
authors.affiliation: University of Illinois Hospital and Health Sciences System, Chicago, IL, USA.
authors.forename: William L
authors.initials: WL
authors.lastname: Galanter
mesh_terms: D002641:Chicago; D016494:Computer Security; D003219:Confidentiality; D057286:Electronic Health Records / Q000592:standards*; D066275:Health Information Exchange / Q000592:standards*; D020408:Health Insurance Portability and Accountability Act; D006801:Humans; D008498:Medical Record Linkage / Q000379:methods*; D012984:Software; D014481:United States
keywords: health information exchange; privacy protection; record linkage