Managerial Epidemiology

Chapter 5

Sources of Data for Use in

Epidemiology

Learning Objectives

• Discuss criteria for assessing the quality

and utility of epidemiologic data

• Indicate privacy and confidentiality issues

that pertain to epidemiologic data

• Discuss the uses, strengths, and

weaknesses of various epidemiologic data

sources

Criteria for the Quality and

Utility of Epidemiologic Data

• Nature of the data

• Availability of the data

• Completeness of population

coverage

– Representativeness

– Generalizability (external validity)

– Thoroughness

• Strengths versus limitations

Nature of the Data

• Refers to the source of data, e.g.,

vital statistics, case registries,

physicians’ records, surveys of the

general population, or hospital and

clinic cases.

• Will affect the types of statistical

analyses and inferences that are

possible.

Availability of the Data

• Refers to investigator’s access to

data.

• For example, medical records and

other data with personal identifiers

may not be used without patients’

consent.

Completeness of Population

Coverage

• Representativeness—the degree to which

a sample resembles a parent population.

• Generalizability (external validity)— ability

to apply findings to a population that did

not participate in the study.

• Thoroughness—the care taken to identify

all cases of a given disease.

Strengths versus Limitations

• The utility of the data for various

types of epidemiologic research.

• Factors inherent in the data may limit

their usefulness.

– Incomplete diagnostic information.

– Case duplication.

Online Sources of Epidemiologic

Data • Online bibliographic databases include

MEDLINE, TOXLINE, and commercial

databases.

• National Library of Medicine’s PubMed®

– MEDLINE is the main part of PubMed®

– Premier source of health-related literature

• TOXLINE—keyed to toxicology and includes

information on drugs and chemicals

Selected Internet Addresses

• American Public Health Association—

http://www.apha.org

• Centers for Disease Control and

Prevention—http://www.cdc.gov

• PubMed®—

http://www.ncbi.nlm.nih.gov/sites/entr

ez

Confidentiality

• Privacy Act of 1974

– Prohibits the release of confidential data without the consent of the individual

• Freedom of Information Act

– Mandates the release of government information to the public, except for personal and medical files

• The Public Health Service Act

– Protects confidentiality of information collected by some federal agencies, e.g., NCHS

The HIPAA Privacy Rule • Refers to the Health Insurance Portability and

Accountability Act of 1996

• Sections of HIPAA “…require the Secretary of

HHS to publicize standards for the electronic

exchange, privacy and security of health

information…”

• Categories of protected health information

pertain to individually identifiable data re:

– The individual’s physical and mental health

– Provision of health care to the individual

– Payment for provision of health care

Data Sharing

• Refers to the voluntary release of

information by one investigator or

institution to another for the purpose of

scientific research.

• Can enhance data quality and increase

knowledge from research.

• Key issue is the primary investigator’s

potential loss of control over information.

Record Linkage

• Joining data from two or more

sources, e.g., employment records

and mortality data.

• Applications include genetic research,

planning of health services, and chronic disease tracking.

Statistics Derived from the

Vital Registration System

• Mortality statistics

• Birth statistics: certificates of birth

and fetal death.

Mortality Statistics

• Mortality data are nearly complete, as most deaths in the U.S. and other developed countries are unlikely to be unreported.

• Death certificates include demographic information about the deceased and cause of death (immediate cause and contributing factors).

Limitations of Mortality Data

• Certification of cause of death.

– For example, in an elderly person with

chronic illness, exact cause of death may be

unclear.

• Lack of standardization of diagnostic criteria.

• Stigma associated with certain diseases, e.g., AIDS, may lead to inaccurate reporting.

Limitations of Mortality Data

(cont’d)

• Errors in coding by nosologist

• Changes in coding

– Revisions in the (ICD) International

Classification of Disease.

– Sudden increases or decreases in a

particular cause of death may be due to changes in coding.

Birth Statistics: Certificates of Birth

and of Fetal Death

• Birth certificate includes information that may affect the neonate, such as congenital malformations, birth weight, and length of gestation.

• Sources of unreliability: – Mothers’ recall of events during pregnancy

may be inaccurate.

– Conditions that affect neonate may not be present at birth.

Birth Statistics (cont’d)

• Varying state requirements for fetal death

certificates.

• Both types of certificates have been used

in studies of environmental influences

upon congenital malformations.

• Both provide nearly complete data.

Reportable Disease Statistics

• Federal and state statutes require health care

providers to report those cases of diseases

classified as reportable and notifiable.

– Include infectious and communicable

diseases that endanger a population, e.g.,

STDs, measles, foodborne illness.

Limitations of Reportable

Disease Statistics

• Possible incompleteness of population

coverage.

– For example, asymptomatic persons

would not seek treatment.

• Failure of physician to fill out required

forms.

• Unwillingness to report cases that carry a social stigma.

Screening Surveys

• Conducted on an ad hoc basis to identify

individuals who may have infectious or

chronic diseases. Examples: breast

cancer screenings, health fairs.

• Clientele are highly selected.

– Individuals who participate are concerned

about the particular health issue.

Multiphasic Screening

• Administration of 2 or more screening

tests during a single screening program

• Ongoing screening programs often are

carried out at worksites.

• Potential biases from worker attrition

• Data can be useful for research on

occupational health problems.

• Data may not contain etiologic information.

Disease Registries • Registry--a centralized database for collection

of data about a disease

• Coding algorithms are used to maintain patient confidentiality.

• Applications of registries:

– Patient tracking

– Identification of trends in rates of disease

– Case-control studies

• Example: SEER program

Surveillance, Epidemiology, and

End Results (SEER) Program

• Conducted by the National Cancer

Institute (NCI)

• Collects cancer data from different cancer

registries across the U.S.

• Provides information about trends in

cancer incidence, mortality, and survival

Morbidity Surveys of the

General Population

• Morbidity surveys collect data on the

health status of a population group.

• Obtain more comprehensive information

than would be available from routinely

collected data

• Example: National Health Interview

Survey

National Health Survey

• Authorized under the National Health Survey Act of 1956 to obtain information about the health of the U.S. population.

• Refers generically to a group of surveys and not a single survey.

• In response to the Act, the National Center for Health Statistics (NCHS) conducts three separate and distinct programs.

NCHS Survey Programs

• National Health Interview Survey (NHIS)

• Health Examination Survey (HES)

• Various surveys of health resources – National Hospital Discharge Survey

– National Ambulatory Medical Care Survey

National Health Interview

Survey (NHIS)

• General household health survey of the

U.S. civilian noninstitutionalized

population

• Studies a comprehensive range of

conditions such as diseases, injuries,

disabilities, and impairments

Health Examination Survey

(HES)

• Provides direct information about morbidity through examinations, measurements, and clinical tests

– Identifies conditions previously unreported or

undiagnosed

– Provides information not previously available

for a defined population

• Now known as the Health and Nutrition Examination Survey (HANES)

Behavioral Risk Factor

Surveillance System (BRFSS)

• Collects data on behaviorally related

phenomena

– Behavioral risks for chronic diseases

– Preventive activities

– Healthcare utilization

• The largest telephone survey in the world

California Health Interview

Survey (CHIS)

• Provides information on the health and demographic characteristics of California residents

• Uses telephone survey methods

• Topics include

– Physical and mental health

– Health behaviors

– Health insurance coverage and utilization

• Conducted on a continuing basis

Insurance Data

• Sources include:

– Social Security--provides data on disability

benefits and Medicare.

– Health insurance--provides data on those

who receive care through a prepaid medical

program.

– Life insurance--provides information on

causes of mortality; also provides results of

physical examinations.

Limitations of Insurance Data

• Data may not be representative of entire population, as the uninsured are excluded.

Clinical Data Sources

• Hospital data

• Diseases treated in special clinics

and hospitals

• Data from physicians’ practices

Hospital Data

• Consists of both inpatient and outpatient data

• Deficiencies of data:

– Not representative of any specific population

– Different information collected on each patient

– Settings may differ according to social class of patients; e.g., specialized clinics, emergency rooms

Diseases Treated in Special

Clinics and Hospitals

• Data cannot be generalized because

patients are a highly selected group.

• Case-control studies can be done with

unusual and rare diseases.

– However, it is not possible to

determine incidence and prevalence

rates without knowing the size of the

denominator.

Data from Physicians’

Practices

• Limited application due to:

– Confidentiality of patient data

– Highly selected group of patients

– Lack of standardization of information

collected

• Useful for the purposes of:

– Verification of self-reports

– Source of exposure data

Absenteeism Data

• Records of absenteeism from work or school

• Possible deficiencies:

– Data omit people who neither work nor

attend school.

– Not all people who are ill take time off.

– Those absent are not necessarily ill.

• Useful for the study of rapidly spreading conditions

School Health Programs

• Provide information about

immunizations, physical exams, and self-

reports of illness

• Have been used in studies of

intelligence, mental retardation, and

disease etiology

• Paffenbarger, et al. used information

from health records of college students

to track causes of chronic diseases.

Morbidity Data from the Armed Forces

• Reports from physicals, hospitalizations, and selective service examinations

• Data have been used for:

– Studies of disease etiology.

• Study of twins serving in Korean War or WWII to

determine influence of “nature and nurture” on

cause of disease.

– Studies investigating genetic factors in obesity

Other Data Sources Relevant

to Epidemiologic Studies

• U.S. Bureau of the Census publications:

– Statistical Abstract of the United States

– County and City Data Book

– Decennial Censuses of Population and

Housing

– Historical Statistics of the United States,

Colonial Time to 1970

U.S. Bureau of the Census

• Provides information on the general, social, and

economic characteristics of the U.S. population

• U.S. Census is administered every 10 years.

– Attempts to account for every person and his

or her residence

– Characterizes population according to sex,

age, family relationships, and other

demographic variables