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Data Anonymisation and Linkage

Data Anonymisation and Linkage. Alison Bell Senior Data Analyst / Programmer Health Informatics Centre (HIC) University of Dundee. What is HIC ?.

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Data Anonymisation and Linkage

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  1. Data Anonymisation and Linkage Alison Bell Senior Data Analyst / Programmer Health Informatics Centre (HIC) University of Dundee

  2. What is HIC ? The Health Informatics Centre (HIC) is a partnership between the University of Dundee, NHS Tayside and the Information Services Division of NHS National Services (ISD). It’s a shared research resource with strong scientific traditions, built on MEMO work since early 1980s. HIC provides authorised researchers and others with anonymised extracts of information derived from person-specific data sets captured by the NHS, University of Dundee researchers and others, to help them answer research questions and address important quality and patient safety issues.

  3. HIC Structures • Staff and facilities managed by HIC Executive • User input: HIC User Group • Governance • - Confidentiality & Privacy Advisory Committee (HICCPAC) • - Users Forum • - Annual External Audit

  4. Issues that HIC addresses Governance: linkage then anonymisation carried out in NHS domain Trust in access to NHS data through approved SOPs, Privacy Advisory Committee, “Clinical Information Bureau” Deterministic linkagevia single patient identifier Continually improving data qualitythrough clinical use of data & HIC Users’ Group Ecological fallacy: person, not practice, based data

  5. Information governance Physical security: • Isolation of servers holding identifiable data and staff working with it • Reliable backup and recovery mechanisms • Separation of functions on NHSNet, JANET Governed by Confidentiality & Privacy Advisory Committee • Members include lawyer, GP, Caldicott Guardians, Director Public Health Management tools: • Standard Operating Procedure • Adverse incident reporting mechanism on intranet • Project management system enforces SOP • Annual external audit by information security experts & table of issues reviewed monthly by HIC Exec

  6. HIC Standard Operating Procedure Covers: • Acquisition & anonymisation of datasets • Requesting access to data • Project level anonymisation (Pro-CHI) • Release & archival of datasets • Reversal of anonymisation Includes: • Definitions • Appendix summarising 8 data protection principles • Declaration & signature HIC has Caldicott & Ethics approval to supply anonymised data to approved research projects

  7. HIC project management system • Allocates each project a unique ID • Captures: • Identity & contact details of “approved researcher” • Project funder • Project abstract • Copies of approval from Ethics & Caldicott (if required), NHS R&D, protocol • Data sources and versions • Exact syntax used to generate & link data extracts • Audit trail of all data releases • Exact location of archived datasets once project complete

  8. Available HIC Data • HIC hosts a large number of Tayside data sets received from various sources (ISD, PSD, GRO, Ninewells Labs etc.) • These cover various populations, time periods and use a variety of coding systems • Each of these patient-specific data sets contain the patient CHI number allowing linkage across multiple data sets • HIC currently has approval to provide Tayside data only, but seeking to extend to Fife & Glasgow soon

  9. CHI labelled data Fully anonymised but linked data CHI labelled data How data are linked and anonymised Paper prescription-ID Find and enter CHI Paper prescription - ID Drug data-CHI Paper prescription - ID Drug data-CHI Drug data-CHI Drug data, lab data-CHI Drug data, lab data Link using CHI Delete CHI Add Pro-CHI Drug data, lab data-CHI Drug data, lab data Drug data, lab data-CHI Drug data, lab data Find CHI Lab result-ID Lab result - ID Lab data-CHI Lab result - ID Lab data-CHI Lab data-CHI Analysis Data Provider - mainly NHS Clinical Information Bureau Academia

  10. Anonymisation Process • Every research dataset has its own project level anonymisation (Pro-CHI) applied to the data before being released to a researcher. • Purpose written software generates the Pro-CHI based on the Project Management unique ID & the CHI • A 3-digit alphabetic code is generated based on the PM ID (to base26) eg. 165 translates to agj • The last 7 digits are randomly generated • Eg. (CHI)1212345678 = (Pro-CHI) agj8394601 under project 165 • All research data relating to a specific project will have the same 3-digit code. • All other patient identifiers are removed (eg name, address etc) • Other anonymisations are performed – anon DOB, anon GP code • If any identifiable data is required, specific Caldicott approval must be granted

  11. A bit more about the prescribing data set ….. • The Tayside prescribing data set is unique to the UK. • It is a database of all Tayside encashed prescriptions, including CHI, date prescribed and drugs dispensed. • Prior to 2005, paper prescriptions were scanned by the data entry clerks and all prescription details were entered manually using a purpose-built application. • Since 2005, PSD have been automatically sending HIC the scanned prescription images and associated data. • 300,000 prescriptions per month (total 14.5m in dbase from 2005) • 13 GB .tif images per month (front and back) • 17% (50,000) still require data entry (CHI) each month

  12. Users of HIC data 2004-9 93 projects totalling £16m (£3.2m pa), inc: • Diabetes research • Maternal & Child Health • Dental Health Services Research • Cardiovascular • Genetics • Health Informatics • Drug Safety • Scottish Longitudinal Studies Centre

  13. Examples of recent studies using prescription data • Influence of apo-e & other genotypes on response to statins (Louise Donnelly, GSK studentship) • Adherence: to insulin (Morris et al, Lancet); to sulphonylureas (Donnan et al Diab Med, Evans et al Diab Med) • Drug safety studies: corticosteroids and risk of fracture (Donnan et al); statins (Li Wei); methadone (Fahey); methotrexate (Guthrie) • Markers for co-morbidity, eg. emergency admissions study (Donnan)

  14. Future plans • Enhanced HIC service including • Programming, statistical, Clinical Trials Unit support, data management • Scaling up to a Scotland-wide Health Programme (SHIP) • Rolling out novel research data mechanism to further improve information governance: MILA • Pilot study – obtaining identifiable retinal images from Ninewells eye clinic (300 images @ 5 MB each) & anonymise for research

  15. Conventional Record-Linkage Confidentiality? Governance? Scalability? Recipient Generate identifier substitutions and deliver to recipient Data sources Data sources Trusted repository (PAC Oversight and SOPs)

  16. MILA: Multi-Institutional Linkage & Anonymisation (89) Recipient (17) (17 -> 2) (89 -> 2) B (89 -> 2) Confidentiality  Governance  Scalability  A (17 -> 2) Person (IDA, IDB, …) Person 1 (17, 89, …) Person 2 (…) … Linker (holds identifiers) Data sources

  17. Some research data mechanisms

  18. How MILA matches the requirements

  19. Sir Alan Langlands, September 2005

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