Linking Individual Records from Multiple Large Databases; a short History and Practical Solution

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 PermanenetePasadena California


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.


Medical Records Evolution-

Stone Age - Patient Charts & Manual Logs Industrial Revolution - Simple EDP Electronic Age - Computers


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.


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.


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.


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.


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


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!”


Linkage Problems

False linkagesRelease of confidential informationSpecial populations• Immigrants• Indigenous populations• Character-based languages.


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


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)


HASAC Recommendations

1st 4 digits of last name1st 2 digits of first nameMiddle initialGenderDate of Birth


HASAC Results

696,000 persons

17 duplicate identifiers

Duplicates eliminated with a tie-breaker:

Place of Birth


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.


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.



Data sources Birth Certificates Death Certificates State disability files State Welfare Records Public Health Centers Medicaid Programs for uninsured children Hospitals School Records



Matrix of data from all sources showed all contained Name Date of Birth Gender

Modified HASAC number selectedProject failed……. Why?



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.


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.


Immunization Registries Data sources

MMIS

________________SIIS HUB

LargeProvider(HMO)

RegionalRegistry

RegionalRegistry

ProviderOther

SharingPartner

Provider OtherSharingPartner

SharingPartners


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.


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


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


KITS Linkage Problems

Day of birth proved to be more accurate than month

1st name often misspelled Gender listed incorrectly Twins had same first and last names,

with only differing middle names etc., etc., etc.


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.


Uses of Linked Data I

CareExamine the health of the public Avoid duplicate treatmentsReveal who needs preventive care Continuity of careGenerate immunization and disease registers

ManagementExamine the health of the health care systemCreate health indicators

Research


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.


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.


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.

Documents

Linking Individual Records from Multiple Large Databases; a short History and Practical Solution