title: A Protocol for the secure linking of registries for HPV surveillance.
abstract: BACKGROUND
  In order to monitor the effectiveness of HPV vaccination in Canada the linkage of multiple data registries may be required. These registries may not always be managed by the same organization and, furthermore, privacy legislation or practices may restrict any data linkages of records that can actually be done among registries. The objective of this study was to develop a secure protocol for linking data from different registries and to allow on-going monitoring of HPV vaccine effectiveness.
  
  
  METHODS
  A secure linking protocol, using commutative hash functions and secure multi-party computation techniques was developed. This protocol allows for the exact matching of records among registries and the computation of statistics on the linked data while meeting five practical requirements to ensure patient confidentiality and privacy. The statistics considered were: odds ratio and its confidence interval, chi-square test, and relative risk and its confidence interval. Additional statistics on contingency tables, such as other measures of association, can be added using the same principles presented. The computation time performance of this protocol was evaluated.
  
  
  RESULTS
  The protocol has acceptable computation time and scales linearly with the size of the data set and the size of the contingency table. The worse case computation time for up to 100,000 patients returned by each query and a 16 cell contingency table is less than 4 hours for basic statistics, and the best case is under 3 hours.
  
  
  CONCLUSIONS
  A computationally practical protocol for the secure linking of data from multiple registries has been demonstrated in the context of HPV vaccine initiative impact assessment. The basic protocol can be generalized to the surveillance of other conditions, diseases, or vaccination programs.
authors: Electronic Health Information Laboratory, Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada. kelemam@uottawa.ca
authors: Khaled
authors: K
authors: El Emam
authors: Saeed
authors: S
authors: Samet
authors: Jun
authors: J
authors: Hu
authors: Liam
authors: L
authors: Peyton
authors: Craig
authors: C
authors: Earle
authors: Gayatri C
authors: GC
authors: Jayaraman
authors: Tom
authors: T
authors: Wong
authors: Murat
authors: M
authors: Kantarcioglu
authors: Fida
authors: F
authors: Dankar
authors: Aleksander
authors: A
authors: Essex
mesh_terms: D000465:Algorithms; D005260:Female; D006801:Humans; D008297:Male; D027383:Papillomaviridae; D030361:Papillomavirus Infections / Q000453:epidemiology* / Q000517:prevention & control; D053918:Papillomavirus Vaccines / Q000627:therapeutic use; D011159:Population Surveillance / Q000379:methods*; D012042:Registries
chemical_list: D053918:Papillomavirus Vaccines