1. Southern California Kaiser Permanente Linking Individual Records from Multiple Large Databases; a short History and Practical Solution Marlene M. Lugg, DrPH Research Scientist Southern California Kaiser Permanenete Pasadena California

2. Southern California Kaiser Permanente Medical Record Linkage; What is it? The process of bringing together two or more records relating to the same entity - person, family, event, hospital. Deterministic – agreement on 1 or more variables; rules based decision tables Probabilistic – mathematical theory developed by Fellegi and Sunter; utilizes software using different weights on each field.

3. Southern California Kaiser Permanente Medical Records Evolution-  Stone Age - Patient Charts & Manual Logs  Industrial Revolution - Simple EDP  Electronic Age - Computers

4. Southern California Kaiser Permanente Stone Age –Some Early History  Paintings and writings on stone (Paleolithic period) no name or ID.  Western Australia’s first hospital was a merchant ship grounded off Fremantle. Medical records consisted of one line on admission and one on discharge.  Later, more detailed charts kept in doctor’s office, usually filed by patient name.

5. Southern California Kaiser Permanente Industrial Revolution I: included simple ADP  Separate charts for each hospital admission. Each person had as many charts as he/she had admissions.  Terminal digit filing system, along with Patient Index, lead to combining all of a patient’s admissions into one chart.  Ambulatory Care data was most often separate unless clinic was part of the hospital.

6. Southern California Kaiser Permanente Industrial Revolution II: included mainframe computers  1946 - H. L. Dunn (USA), initial ideas for linking life data.  1950’s - H B Newcombe (Canada) laid probabilistic foundations of modern linkage theory into family groups.  1962 - Oxford Record Linkage Study –Sir Donald Acheson linked birth, morbidity and mortality data for Oxford area.

7. Southern California Kaiser Permanente Electronic Age – computerized systems  Made probabilistic linkage possible for large databases. (in house, between facilities, local, state-wide, national).  Provides advantages of quality control, speed, consistency and reproducibility.  Electronic Medical Records can make data available over wide geographic areas.

8. Southern California Kaiser Permanente Criteria for Medical Record Linkage for large scale or national linkage I  Universality  Availability  Ease of implementation and maintenance  Minimal inconvenience patient and provider  Unique  Economic  Permanent

9. Southern California Kaiser Permanente Criteria for Medical Record Linkage for large scale or national linkage II Linkage should be created from personal data readily available and provided by the patient, and No Identity Card or number should be required. “Patient always has the correct linkage number with him/her!”

10. Southern California Kaiser Permanente Linkage Problems False linkages Release of confidential information Special populations Immigrants Indigenous populations Character-based languages.

11. Southern California Kaiser Permanente Find the Error David L. James, born March 16, 2003 @ West Hospital Ambulatory care visit on May 29, 2004 for 1-year old immunizations. Physician found Medical Record entry that this child had the immunizations 3 weeks previously. Parent denied this. Error? Twins? David L. James, born March 16, 2003 @ West Hospital Born at the same hospital, same day, same name, same gender, but different parents, and was found to be a different child. Different MRN assigned; records divided accordingly

12. Southern California Kaiser Permanente Australian National Hospital and Allied Services Advisory Council -1973 Studied ways to create a uniform personal identifier using personal data readily available to the patient and health care provider without recalling a medical record number, or finding a membership card. (HASAC Identifier)

13. Southern California Kaiser Permanente HASAC Recommendations 1 st 4 digits of last name 1 st 2 digits of first name Middle initial Gender Date of Birth

14. Southern California Kaiser Permanente HASAC Results 696,000 persons 17 duplicate identifiers Duplicates eliminated with a tie-breaker: Place of Birth

15. Southern California Kaiser Permanente Further Use of HASAC Identifier In 1983-4, Australia implemented national health insurance. A statistical algorithm was applied to the HASAC Identifier for privacy, and the new number became the National Health Insurance number.

16. Southern California Kaiser Permanente California Child Health Data 2003 CA Health Information for Policy Project’s Interagency Working Party wanted to link children from ten different state and local databases in order to provide continuity of care, and eliminate duplicative care.

17. Southern California Kaiser Permanente California Child Health Data 2003 Data sources  Birth Certificates  Death Certificates  State disability files  State Welfare Records  Public Health Centers  Medicaid  Programs for uninsured children  Hospitals  School Records

18. Southern California Kaiser Permanente California Child Health Data 2003 Matrix of data from all sources showed all contained  Name  Date of Birth  Gender Modified HASAC number selected Project failed……. Why?

19. Southern California Kaiser Permanente California Child Health Data 2003 Politics intervened One of the committee members insisted on using mother’s maiden name as a tie-breaker, instead of place of birth. Committee agreed. Most large heath care organizations did not have mother’s maiden name in their records, and it was too expensive to collect it retrospectively.

20. Southern California Kaiser Permanente Immunization Registries  Immunization registries play a vital role in Vaccine Safety Monitoring and Studies.  State –wide Immunization registries keep a person’s record in one place, regardless of how many provider sites administered the vaccines.  Linkage necessary for de-duplication of immunizations and making sure no patient has more than one MRN, nor shares an MRN with another patient.

21. Southern California Kaiser Permanente Immunization Registries Data sources

22. Southern California Kaiser Permanente In California, The Kaiser Immunization Tracking System (KITS), covers 33% of all California children. The Southern California KITS contains 48 million inoculations from Kaiser facilities and immunization records provided from other sources.

23. Southern California Kaiser Permanente Kaiser Permanente - Non-profit group model HMO Comprehensive Health Care Southern California  For 3.0 million members and 40,000 births/year  At 12 hospital/medical centers and 90+ outpatient clinics  By over 3,000 providers, including 800+ in pediatric primary care

24. Southern California Kaiser Permanente KITS linkage Linkage results: Twenty-six algorithms developed to be run automatically  85% linked with Medical Record Number alone  90.0% linked with MRN, last name, first name, gender, DOB  97.1% linked after first 5 algorithms  99.1% linked after 16 algorithms  99.7% linked after 26 algorithms

25. Southern California Kaiser Permanente KITS Linkage Problems  Day of birth proved to be more accurate than month  1 st name often misspelled  Gender listed incorrectly  Twins had same first and last names, with only differing middle names  etc., etc., etc.

26. Southern California Kaiser Permanente Kaiser Permanente Southern California Data Consolidation Current data consolidation method used by Southern California Kaiser Permanente utilizes algorithm using personal data from the membership file, hospital discharges, and ambulatory care clinic data, with a 99% linkage rate. Lists all MRN’s assigned to an individual, rather than correcting them.

27. Southern California Kaiser Permanente Uses of Linked Data I Care Examine the health of the public Avoid duplicate treatments Reveal who needs preventive care Continuity of care Generate immunization and disease registers Management Examine the health of the health care system Create health indicators Research

28. Southern California Kaiser Permanente Uses of Linked Data II Scottish Health Information System  Study of unscheduled care patient pathways.  Impact of road safety cameras –linkage of police records to hospital inpatient data.  Risk of skin cancer after phototherapy for neonatal jaundice.  Can link with census data, which is not possible in some countries.

29. Southern California Kaiser Permanente Summary and Advice Probabilistic linkage is excellent but involves more time, money and staff, which may not available. A less involved linkage such as the HASAC method, modified for local needs will often yield excellent results in a cost-effective manner.

30. Southern California Kaiser Permanente Acknowledgements: A sincere thank you to all my former staff at the Statistics Branch, Health Department of Western Australia, students and staff at UCLA, and colleagues at Kaiser Permanente, who have spent innumerable hours working together on Medical Record Linkage.