title: Assessing Hepatitis C Burden and Treatment Effectiveness through the British Columbia Hepatitis Testers Cohort (BC-HTC): Design and Characteristics of Linked and Unlinked Participants.
abstract: BACKGROUND
  The British Columbia (BC) Hepatitis Testers Cohort (BC-HTC) was established to assess and monitor hepatitis C (HCV) epidemiology, cost of illness and treatment effectiveness in BC, Canada. In this paper, we describe the cohort construction, data linkage process, linkage yields, and comparison of the characteristics of linked and unlinked individuals.
  
  
  METHODS
  The BC-HTC includes all individuals tested for HCV and/or HIV or reported as a case of HCV, hepatitis B (HBV), HIV or active tuberculosis (TB) in BC linked with the provincial health insurance client roster, medical visits, hospitalizations, drug prescriptions, the cancer registry and mortality data using unique personal health numbers. The cohort includes data since inception (1990/1992) of each database until 2012/2013 with plans for annual updates. We computed linkage rates by year and compared the characteristics of linked and unlinked individuals.
  
  
  RESULTS
  Of 2,656,323 unique individuals available in the laboratory and surveillance data, 1,427,917(54%) were included in the final linked cohort, including about 1.15 million tested for HCV and about 1.02 million tested for HIV. The linkage rate was 86% for HCV tests, 89% for HCV cases, 95% for active TB cases, 48% for HIV tests and 36% for HIV cases. Linkage rates increased from 40% for HCV negatives and 70% for HCV positives in 1992 to ~90% after 2005. Linkage rates were lower for males, younger age at testing, and those with unknown residence location. Linkage rates for HCV testers co-infected with HIV, HBV or TB were very high (90-100%).
  
  
  CONCLUSIONS
  Linkage rates increased over time related to improvements in completeness of identifiers in laboratory, surveillance, and registry databases. Linkage rates were higher for HCV than HIV testers, those testing positive, older individuals, and females. Data from the cohort provide essential information to support the development of prevention, care and treatment initiatives for those infected with HCV.
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.|School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Naveed Zafar
authors.initials: NZ
authors.lastname: Janjua
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.
authors.forename: Margot
authors.initials: M
authors.lastname: Kuo
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.
authors.forename: Mei
authors.initials: M
authors.lastname: Chong
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.
authors.forename: Amanda
authors.initials: A
authors.lastname: Yu
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.
authors.forename: Maria
authors.initials: M
authors.lastname: Alvarez
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.
authors.forename: Darrel
authors.initials: D
authors.lastname: Cook
authors.affiliation: British Columbia Ministry of Health, Victoria, BC, Canada.
authors.forename: Rosemary
authors.initials: R
authors.lastname: Armour
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.
authors.forename: Ciaran
authors.initials: C
authors.lastname: Aiken
authors.affiliation: British Columbia Ministry of Health, Victoria, BC, Canada.
authors.forename: Karen
authors.initials: K
authors.lastname: Li
authors.affiliation: Performance Measurement & Reporting, Provincial Health Services Authority, Vancouver, BC, Canada.
authors.forename: Seyed Ali
authors.initials: SA
authors.lastname: Mussavi Rizi
authors.affiliation: BC Cancer Agency, Vancouver, BC, Canada.
authors.forename: Ryan
authors.initials: R
authors.lastname: Woods
authors.affiliation: British Columbia Ministry of Health, Victoria, BC, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Godfrey
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.|School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Wong
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.|School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada.|Ontario HIV Treatment Network, Toronto, ON, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Gilbert
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.|School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Tyndall
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, BC, Canada.|Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Mel
authors.initials: M
authors.lastname: Krajden
mesh_terms: D001955:British Columbia / Q000453:epidemiology; D017281:Cost of Illness; D016208:Databases, Factual; D062665:Epidemiological Monitoring; D005260:Female; D005500:Follow-Up Studies; D006526:Hepatitis C / Q000453:epidemiology*; D006801:Humans; D008297:Male; D012189:Retrospective Studies