The secondary use of patient data for research.

Dr. Spiros DenaxasClinical Epidemiology

Epidemiology and Public HealthUCL Medical School

s.denaxas@ucl.ac.uk

Structure

Epidemiological studiesPatient data enhancing existing epidemiological

studiesPatient data for performing in vitro epidemiological

studiesThe future of large-scale epidemiological studies

Learning outcomes

Epidemiology definedTimeline of cohort studiesChallenges using clinical data for researchEHR linkingValue of linking different data repositories

Clinical epidemiology

“The application of epidemiological knowledge, reasoning, and methods to study clinical

issues and improve clinical care. Research often addresses aetiological, diagnostic,

therapeutic, and prognostic medical issues, is conducted in clinical settings led by

clinicians and had patients as the subjects of the study.”

J. M. Last, A Dictionary of Epidemiology

Coronary Heart Disease (CHD)

Coronary Heart Disease (CHD) is the leading cause of death in the UK

~180.000 CHD deaths in the UK p.a.Collective term for diseases which occur due to

atheroma building up in artery walls.Prevalence: ~2.7MRisk factors: smoking, diabetes, obesity, diet,

physical activity, SES, mental health

Stable angina

Early manifestation: angina (chest pain)Symptoms: chest pain, feeling of heartburn,

palpitations, shortness of breathTriggered by:

− Exercise− Cold weather− Stress

Myocardial Infarction (MI)

Myocardial Infarction: Necrosis of the myocardial tissue due to ischaemia due to a thrombus

Symptoms: gripping chest pain, dizziness, overwhelming anxiety, shortness of breath

~124.000 MI’s in the UK per year (BHF, Statistics 2010)

(BHF, Statistics 2010)

Wisdom

“It is only by collecting data and using them that you get sense”

William Osler, Aequanimitas, 1928

Timeline of disease

Start with a healthy population

Some people drop out

Wait

Some people get diagnosed

Some people get events (and some die)

Gathering as much as possible

Medical screening clinics− Anthropomorphic measurements− Blood / urine samples− Other measurements

Repeat questionnaires− Life style− SES− Activity

Smoking

Only one problem

"The problem with quotes on the Internet is that it is hard to verify their authenticity" - Abraham Lincoln

Self-reporting data

People forget − or chose to forget

TemporalitySubjective by definitionDifferent people -> different thresholdsAscertainment

Periodontal disease

Seven cohorts, multiple papersRelative risk 1.24 (95% CI 1.01-1.51) to 1.34 (95%

CI 1.10 – 1.63)

Humphrey LL, Fu R, Buckley DI, Freeman M, Helfand M. Periodontal disease and coronary heart disease incidence: a systematic review and meta-analysis. J Gen Intern Med. 2008.

Primary care data

First line of care in the UK: the GPCentered around consultationsDiagnostic information, prescriptions, referrals,

additional measurementsInformation is recorded using a standard clinical

terminology system (Read)

Sample primary care data

Advantages

Majority of people registered with GPData collected at large scaleData recorded at regular intervalsGreater data granularityHigh data completeness on comorbiditiesIntroduction of QoF

Problems: conflicting information

Problems

Lack of streamlined approach to obtain dataHow?

ConflictsMeasurement error (BP,HR)Information error (aspirin)

Pathway of disease

Secondary care data

Hospital Episode Statistics (HES)Data warehouse of all admissions to NHS

hospitalsInformation is recorded using the International

Classification of Diseases ontology 10th revision (ICD10)

Sample secondary care data

Secondary care data: advantages

Extremely high data completenessComplete picture of admissions and re-

admissions to secondary careProvide information where not possible to collect

(admission for severe depression episode)

Secondary care data: disadvantages

Data collected for administrative purposesCoding of individual entries is not done exclusively

by doctorsCoding standards change over time

− ICD9 to ICD10− ICD10-CM− SNOMED-CT

Pathway of disease

Registries

“The collection of information for its own sake is of doubtful value unless it is acted upon. Community registers should not become the equivalent of village war memorials.”

Hugh Tunstall Pedoe 1978

Myocardial Ischaemia National Audit Project (MINAP)

Established in 2000All hospitals in England and Wales submit data~600.000 records~120 fields on medical history, medication,

admission and dischargeInitially setup for auditing purposes

Myocardial Ischaemia National Audit Project (MINAP): advantages

Coronary phenotype information not available elsewhere

ST elevation MI (STEMI)Non ST elevation MI (nSTEMI)

Added flexibility (markers, ECG etc)

Myocardial Ischaemia National Audit Project (MINAP): disadvantages

Data collected and recorded on a voluntary basisLess severe cases (nSTEMI) are not always

submitted due to lack of resources (MINAP Public Report 2011)

On its own, provides little information on pre-event pathway

Registries

International (Sweden RIKS-HIA)In registry randomization Harmonization between types

Pathway of disease

Office for National Statistics (ONS) Mortality Data

Medical Research Information Service (MRIS)Current status service

− Date and place of death− Causes of death (underlying and primary)− Occupation

Cause of death certified by medical practitioner

Office for National Statistics (ONS) Mortality Data

Mortality data: advantages

Enable (cheap) long term follow up and establish cause of death.

Provide information where not ethical to collect (cause of death inquiry from spouse)

Pathway of disease

Rare disease?

CHDPrevalence of 2.7M (BHF)

Creutzfeldt–Jakob disease (CJD)1 case per million per year (CDC)

Other?

Novel electronic health record linkages: CALIBER

Cardiovascular disease research using linking bespoke studies and electronic health records.

Bring everything together by linking multiple sources

CALIBER

CALIBER - validation

Two distinct steps

Identify patients

Demographics and timing

Identify events

Timing and consistency

Severity

Problems with EHR linking - governance

Multiple stakeholders

Different methods of access

Primary care

Attitude towards linking

Problems with EHR linking - data

Unequal granularity between sources

Coding

Timing issues

Resurrections

Conflicting information

Shifting patterns

Not just for CHD

Bespoke cohorts can be enhanced through linking− Ascertainment − Validation

Similar approaches work for other diseases− Cancer registries− HIV registries− Infection / HPA

So much more…!

Plethora of information enclosed within hospital EPR systems− ECG data− Imaging, sound− Routine blood results− A&E records− Ambulance records

So much more…!

Plethora of information contained in disparate information systems− Pension records− Criminal records− National Treatment Agency− Port Health Screening datasets

Conclusions

Routinely collected data facilitates research which might have previously been impossible to perform

Data is not perfect, must be treated with cautionThe future is in linking multiple disparate sources… and amalgamating different disciplines together

Thank you.