1. NHS Health Scotland Linking the Scottish Health Survey to hospitalisation and mortality records in Scotland Bruce Whyte July 2003

2. NHS Health Scotland Overview: u Record Linkage Techniques u Scotlands Linked Health Data Sets u Linkage of Scottish Health Survey u Potential of Dataset

3. NHS Health Scotland Record linkage techniques Aim: To establish which health related records belong to the same individual.

4. NHS Health Scotland Record linkage techniques: Linked v. unlinked data

5. NHS Health Scotland Record linkage techniques: Linkage Process u Historical Background u Why not use a unique identifier ?? u How are records linked? u Exact matching: 85%-ish accurate? u Probability matching: 99% accurate

6. NHS Health Scotland Record linkage techniques: Linkage Process Probability matching rather than exact matching...

7. NHS Health Scotland Record linkage techniques: Probability matching u Calculate odds u Core linking items (soundex of surname, first initial, date of birth, sex, postcode) u Additional linking items (e.g. CRN, Birthweight) u Weights, score & threshold u Results: u Very bad u Very good u Borderline

8. NHS Health Scotland Hospital Discharges SMR1 Psychiatric inpatient SMR4 SOCRATES/ SMR6 RG Death Records RG Births Records Maternity (SMR2) Neo-Natal (SMR11) RG Still Births/Infant Deaths External Data Other ISD Data 1981 to Dec 2002 1980 to 2000 Linked dataLinkable data Scotlands Linked Health Data Sets

9. NHS Health Scotland Scotlands Linked Data Sets - Example of patient history

10. NHS Health Scotland Linkage of Scottish Health Survey AcuteSMR1s 1981-2002 Psych. SMR4s 1981-2002 CancerSMR6s 1981-2002 DeathsGRO(S) 1981-2002 Scottish Health Survey Records: 7,363 adults aged 16-64 in 1995 8305 adults aged 16-74 in 1998

11. NHS Health Scotland Linkage of Scottish Health Survey: File structure

12. NHS Health Scotland Potential of Linked Dataset u With hospital and death records u Patient Histories u Patients, episodes & stays u Incidence & prevalence u Readmission rates u Re-operation rates u Clinical Outcome Indicators u With health survey, hospital and death records u Most of the above but using additional socio- economic and behavioural data e.g. analysis of association between risk factors and health outcomes

13. NHS Health Scotland In conclusion u The creation of such a dataset has been made possible by the application of record linkage techniques and availability of national hospitalisation and mortality data u The dataset marries behavioural & socio-economic data with hospitalisation & mortality data for the first time on a national basis within Scotland u Will become increasingly useful over time u Significantly adds to the utility of the Scottish Health Survey as a source of epidemiological data u Probably unique in UK u May facilitate comparisons to similar datasets in Europe u But what do you think?

14. NHS Health Scotland Linking the Scottish Health Survey to hospitalisation and mortality records in Scotland Bruce Whyte July 2003