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EPI 5240:Introduction to Epidemiology

Sources of Information; Disease RegistriesSeptember 21, 2009

Dr. N. Birkett,Department of Epidemiology & Community

Medicine,University of Ottawa

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Session Overview

• Overview sources of information about mortality/morbidity in Canada.

• Review design of disease registries

• Provide examples of registries in Canada.

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Sources of data: Mortality (1)

Vital Statistics• Births, deaths, marriages, etc.• Mostly reported by physicians.• Coded centrally by staff trained to apply ICD, etc.

coding.• Accuracy of information depends on initial effort by

person completing the form• Multiple causes of death coding.• Timeliness of reports is getting better

– 1999 used to be the most recent information published with 2004 for summary mortality data on-line (CANSIM).

– Now can get data up to about 2007.

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Sources of data: Mortality (2)

Canadian Mortality Data-base• Information from all Canadian death certificates

from 1950 to present.• Death certificates (and birth certificates) used

to be publicly available but are not now.• CMDB can be searched electronically (for a

fee) to link subjects to mortality records– ‘GIRLS’

• Completeness is very good; mainly misses out-of-country deaths.

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Sources of data: Morbidity (1)

• Much harder to get information and much less complete (e.g. many diseases/conditions have no routinely available information)

• Good information on– Many infectious diseases– Cancer– Abuse and violence

• Some information, but lower quality, on:– Congenital abnormalities– Vision problems– Diabetes

• Surprisingly poor information on CHD incident cases.

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Sources of data: Morbidity (2)

• Potential sources of information– Disease registries– Surveillance– Reportable diseases– Administrative data

• CIHI• ICES• Saskatchewan Drug Programme• ADRs

– General population surveys– Special targeted surveys

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Sources of data: Morbidity (3)

Disease surveillance• The PHAC runs a large number of surveillance

programmes.– Influenza (fluwatch)– HIV– Injuries– West Nile disease

• Extends to chronic diseases as well.

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Sources of data: Morbidity (4)Disease surveillance• Potential Biases

– Incomplete coverage– Method of disease identification

• Self report• self diagnosis• Lack of confirmatory tests

– Popularity effects• H1N1• Child abuse

• Can pick up epidemics but does not give valid incidence rates– ‘start’ of an epidemic can enhance reporting leading to artefacts in size

of epidemic• Sentinel Practices• Provincial health labs• Ontario Agency for Health Protection and Promotion

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Sources of data: Morbidity (5)

Disease surveillance• Reportable Diseases

– Another way to conduct surveillance– ‘active’

• MD’s must report (by law) any diagnosis of these conditions

– Applies mainly to infectious diseases– Also applies to

• suspected child abuse.• Gun shot victims in hospitals (Ontario)• Many professional duties

– E.g. drug abuse in MD’s.

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Sources of data: Morbidity (5)

CIHI (Canadian Institute for Health Information)• An independent, not-for-profit organization that provides

essential data and analysis on Canada’s health system and the health of Canadians

• URL: http://secure.cihi.ca/cihiweb/dispPage.jsp?cw_page=home_e

• Manages multiple data bases– Health Human Resources– Health Spending– Health Services

• Multiple sources of information including hospital discharges.

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Sources of data: Morbidity (6)

CIHI (cntd)• Sample databases:

– Canadian Medication Incident Reporting and Prevention System

– Continuing Care Reporting System– Discharge Abstract Database– Home Care Reporting System– Hospital Mental Health Database– Hospital Morbidity Database– National Ambulatory Care Reporting System– Therapeutic Abortions Database– National Health Expenditures Database– National Prescription Drug Utilization Information System

• Largely based on discharge diagnoses and information

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Sources of data: Morbidity (7)

CIHI (cntd)• Sample registries:

– Canadian Joint Replacement Registry– Canadian Organ Replacement Registry

• Linked to kidney registry

– National Trauma Registry– Ontario Trauma Registry

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Sources of data: Morbidity (8)

Clinical Data: OHIP, etc.• Contains information included in CIHI but also

information on clinical encounters outside hospital

• ICES – Institute for Clinical Evaluative Services– Funded by Ontario government– Aim is to improve delivery of health care Ontario

residents.– Can collaborate with outside groups but strong

security restrictions on access to data.

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Sources of data: Morbidity (9)

Surveys• Can be targeted at specific conditions (e.g..

Canadian Hypertension Survey) or more general (e.g. National Population Health Survey)

• Most recent surveys in Canada have based on self-reported data– Inaccurate/incomplete diagnoses– Focus on risk behaviours and psychosocial factors

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Sources of data: Morbidity (10)Surveys• Nutrition Canada Survey (1970-72)• Canada Health Survey (1978)• Canadian Heart Health Survey (1988-92)• Canadian Study on Health and Aging (1992)• NPHS (1994, 1996/6 & 1998/9)

– Includes a cohort follow-up component

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Sources of data: Morbidity (11)Surveys• Canadian Community Health Survey

– Started in 2000• Health determinants• Health status• Health services utilization

– 2 year cycle• 130,000 subjects in year 1 of cycle• 35,000 subjects in year 2 of cycle

– No physical measures

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Sources of data: Morbidity (12)Surveys• Canadian Health Measures Survey

– N=5,000– Physical measures

• Anthropometry• Cardio fitness• Musculoskeletal fitness• Physical Activity• Spirometry• Oral Health

– Blood and urine sample– ‘in the field’: 2006-8

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Sources of data: morbidity (13)Surveys• Canadian Cohort Studies

– A number of large-scale cohorts are just getting started.

– Cancer– CHD– Healthy Aging– Childhood development

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Registries (1)

• A list or database of people with a pre-defined condition or illness – Ideally, will include ALL people with the condition– Often, will only contain a sub-set.

• Population-based vs. clinic/hospital/etc. based– ‘Population-based’ defines a target population and

registers all cases arising from that population– Instead, register all cases treated at a hospital/clinic.

OR ask for volunteers with a disease• Most useful for looking at prognosis

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Registries (2)

Some Methodology Issues• Definition of disease state.

– Classification ‘rules’.• What to do when the ‘rules’ change?

– Need for standard diagnostic criteria/tests– Validity of diagnosis

• False positives• False negatives.

– Example: Cancer• Malignant vs. benign vs. in-situ• Are some cancers excluded

– non-melanoma skin cancer

• Primary vs. metastatic disease• First vs. second (and later) cancers

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Registries (3)

Some Methodology Issues (cntd)• Completeness of capture

– Applies more to population based registries

• Representativeness of registered subjects– Applies more to non-population based registries

• Methods of capturing information required on each subject.– MD information

• Ethical issues; response rate

– Patient contact• Response rate; validity (and knowledge) of information

– Charts, lab reports, etc.

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Registries (4)

Subject Identification• Passive vs. active vs. Other.• Passive

– Subjects identified using existing records with no active reporting by MD, patient, etc.

• Active– MD required to report any one with the diagnosis

• HIV, reportable diseases

• Other– Volunteers– Members of patient support groups

• CNIB• Canadian Diabetes Association

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Registries (5)What data to collect?• Depends on purpose of the registry• Subject ID information

– Unique identifiers are ‘best’• Not in Canada

– Record linkage• Demographic information

– Age, sex, address, date of birth• Diagnostic details

– ICD codes– Lab tests

• Follow-up– Treatments used– Responses and Relapses– Vital Status– Lab tests

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Registries (6)

Uses of Registries• Descriptive epidemiology of disease

– Incidence/mortality rates by age, sex, etc.– Trends in incidence/mortality

• Generate etiological hypotheses• Prognosis• Source of subjects for studies of etiology and

prognosis– Ethical/privacy issues

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Registries (7)

Registries: Cancer• Under provincial jurisdiction

– Mostly, passive identification– Electronic reporting of new cases.– Cancer registration is mandated by law

• Since 1969, all provinces send data to Statistics Canada for entry in Canadian Cancer Registry.– Data is usually 3-4 years behind.– Hard to get access for outside researchers

• Fees• Need every province to give permission.

• Can be used for record linkage– Ethical and privacy issues

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Registries (8)

Registries: Congenital Diseases• BC has most extensive system (Health Status

Registry)– First established in 1952 as voluntary registry of

‘crippled children’ to assist in identifying care needs.– Expanded to include genetic conditions and birth

problems like rubella– Now captures cases based on hospital discharge

summaries.– Good data since 1984, especially for conditions

diagnosed at birth.

• Alberta has a less extensive registry (age<1)

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Registries (9)

Registries: Cardiovascular Disease• No comprehensive CHD registries in Canada• Several groups have local registries of specific

conditions– Acute MI patients– Pacemakers

• Hard to identify cases– Clinical disease vs. atherosclerosis– Sudden death– Non-hospital treatment

• Nova Scotia, Saskatchewan and BC have best information

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Registries (10)

Registries: Renal failure• Canadian Renal Failure Registry

– Started in 1981.– Voluntary– Appears to have been replaced by a broader based

registry collecting cases through hospital discharge summaries:

• Canadian Organ Replacement Registry– Records information on vital organ transplants and

dialysis patients.– Run through CIHI

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Registries (11)

Registries: Miscellaneous• Vision

– CNIB used to run a voluntary registry of people who were legally blind (started in 1918)

– Current status unclear.– Ottawa Eye Institute is currently doing a review of

vision-related registries

• Diabetes Mellitus– Montreal-based registry of IIDM started in 1981– Canadian Diabetes Association maintains record of

members but also includes family and non-patients.

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Registries (12)

Registries: Miscellaneous• Hemophillia

– Canadian Hemophillia Society maintains list of people with hemophillia

• Trauma, winter sports injuries, childhood injuries, etc.– Many are based on hospital discharge information

from CIHI– Variable quality but can be useful.

• Very limited information on mental health and conditions like arthritis

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Summary• Good information on mortality and cancer

incidence• Lack of information for several key health

conditions– Heart disease incidence– Most chronic diseases with non-fatal impact (e.g..

arthritis)

• Reportable diseases help monitor and control infectious diseases