principles of surveillance - global tobacco control · obesity −health behaviors smoking, sexual...

Principles of Surveillance: Jonathan Samet, MD, MS

1

© 2007 Johns Hopkins Bloomberg School of Public Health

Principles of Surveillance

Jonathan Samet, MD, MSJohns Hopkins Bloomberg School of Public Health

2© 2007 Johns Hopkins Bloomberg School of Public Health

Learning Objectives

Define the basic terms related to surveillance

Specify characteristics of surveillance systems for differentobjectives

Describe selected major surveillance systems


2


Uses of Morbidity and Mortality Data

1. Hypothesis generation

2. Health planning

3. Program evaluation

4. Surveillance


Surveillance

“Ongoing, systematic collection, analysis, and interpretationof health-related data essential to the planning,implementation, and evaluation of public health practice,closely integrated with the timely dissemination of these datato those responsible for prevention and control.”

— U.S. Centers for Disease Control and Prevention


3


Information Loop of Public Health Surveillance

Source: adapted by CTLT from http://www.cdc.gov/epo/dphsi/phs/overview.htm


Immediate Detection of . . .

Epidemics− Established agents− Emerging agents

Newly emerging health problems

Changes in health practices

Changes in antibiotic resistance

Chemical and biological terrorism

Source: Thacker and Stroup. (1994).


4


Periodic Dissemination for . . .

Estimating the magnitude ofthe health problem, includingcosts

Assessing control activities

Setting research priorities

Testing hypotheses

Facilitating planning

Monitoring risk factors

Monitoring changes in healthpractices




Archival Information for . . .

Describing the natural history of disease

Facilitating epidemiologic and laboratory research

Validating the use of preliminary data

Setting research priorities

Documenting distribution and spread


5


Langmuir on Surveillance

“Surveillance, when applied to a disease, means thecontinued watchfulness over the distribution and trends ofincidence through the systematic collection, consolidation,and evaluation of morbidity and mortality reports and otherrelevant data.”

— Alexander Langmuir


From Vector to Agent to Disease: Surveillance Points


6


Points for Surveillance Example: Tobacco


Modeling a Surveillance System

Source: Teutsch and Churchill. (2000).


7


Surveillance Systems: Some Characteristics

Geographic scale: local to global

Event identification: active or passive

Scope: all or sentinel events

Focus on monitoring: vector → agent → outcome

Purpose: tracking or alarm





8


Occurrence of an Event: Kind of Event

What kind of an event?− Exposure

Exposure to air pollution, bio-monitoring− Disease

Communicable diseases, chronic diseases, syndromes− Injuries

Motor vehicle accidents, homicide− Health risk factors

Obesity− Health behaviors

Smoking, sexual behavior, substance use


What do you want to do a surveillance of?− Exposure

Agents Biomarkers

− Exposure determinants Behaviors Risk factors Vectors Host characteristics Reservoirs

− Health outcomes Disease Death Medical care

Occurrence of an Event: Surveillance of What?


9


WHO Global Tobacco Surveillance

World Health Survey− Household survey of adults (18+) conducted in 70 countries in

2002–2003

STEPwise Approach to Surveillance (STEPS)− Modular survey of chronic disease risk factors

Global Youth Tobacco Survey− School-based survey− Global Adult Tobacco Survey (planned)


Occurrence of an Event: What Type of System?

What type of system would work best?− Universal: population tracking

Choose entire population or a representative sample tomonitor for condition of interest (measles, obesity,bioterrorism agents)

− Sentinel: “warning” signs Choose key “location” to monitor for condition of

interest (e.g., unusual disease) “Locations” might include sites, events, providers,

animals, vectors Choose a “location” that is most susceptible to change


10


Capturing an Event: Approaches

Active− Periodic solicitation of case reports from reporting sources,

such as physicians, hospitals, laboratories, etc.

Passive− Relies on health care providers to report on their own

initiative− Must make this reporting process simple and time efficient


Active−Advantages

Can be very sensitive Can collect more

detailed information May be more

representative−Disadvantages

Costly Labor intensive Difficult to sustain

over time

Active vs. Passive: Advantages and Disadvantages

Passive−Advantages

Less costly Eager to design and

carry out Useful for monitoring

trends over time−Disadvantages

Low sensitivity Amount of data

available is limited May not be

representative


11


Active: SEER Cancer Registry

Source: http://seer.cancer.gov


Passive: CDC Notifiable Diseases

Provisional Cases of Selected Notifiable Diseases, United States,Week Ending July 16, 2005*

Source: U.S. Centers for Disease Control. (2005).

* Incidence data for reporting year 2005 is provisional

ChlamydiaAIDSReporting Area

Cum. 2004Cum. 2005Cum. 2004Cum. 2005

9,89110,433374386South Carolina

15,19817,485333531North Carolina

1,4931,3503036West Virginia

11,73210,550329307Virginia

1,9101,970355467District of Columbia

10,0099,692686812Maryland

1,5141,72980100Delaware

91,83090,6876,0226,473South Atlantic


12





Processing and Analyzing the Event

How do you detect a signal?

Data capture/editing/management

Analytical approaches

Statistical approaches


13


Examine the Event by Person, Place, and Time

By person: demographics, lifestyle, risk factors

By place: GIS mapping

By time: epidemic curve, time series analysis


By Place: GIS Mapping

GIS: geographic information systems− GIS links location to information (such as people to addresses,

buildings to parcels, or streets within a network) and layersthat information to give you a better understanding of how itall interrelates

− You choose what layers to combine based on your purpose


14


Image source: adapted by CTLT from U.S. Centers for Disease Control and Prevention. (2005).

By Time: Time Series

Time series analysis accounts for the fact that data points takenover time may have an internal structure (such as trend orseasonal variation) that should be accounted for


By Person: Demographics

Age

Race/ethnicity

Occupation

Socioeconomic status

Sex


15


By Place

Small areas

Governmental units

Nations

Unit chosen to examine is determined by the availability of dataon particular geographic scales


Source: U.S. National Cancer Institute. (1999).

Cancer Mortality Rates, by State


16


Heart Disease Death Rates: 1991–1995

Source: U.S. Centers for Disease Control and Prevention.


Male Lung Cancer Incidence Rate per 100,000

Source: adapted by CTLT from GLOBOCAN. (2002). IARC.


17


Female Lung Cancer Incidence Rate per 100,000

Source: adapted by CTLT from GLOBOCAN. (2002). IARC.





18


Disseminating the Information

Process information for your audience− Broadcast faxes, email, mailings to dissemination lists

Locally, to clinicians Regionally, to health departments

− Web sites− Journal articles− Media


Tobacco Use Information Systems

Global InfoBase− Data repository for chronic

disease risk factorprevalence, includingtobacco use

− Summarized inSurveillance of Risk FactorsReport (SuRF)

Global Information System onTobacco Control (GISTOC)− Provides links to tobacco-

related databases

Image source: World Health Organization. (2003 and 2005).


19


World Health Organization: The SuRF Report

Source: The World Health Organization.





20


Model for State-Based Chronic Disease Surveillance

Response

Hypothesis generation

Health planning

Program evaluation

Source: Remington and Goodman. (1999).


Summary

Surveillance takeaways− Ongoing collection− Systematic according to a plan− Results given to those who need to know them− Resulting action is based in evidence gained in the

surveillance system

principles of surveillance - global tobacco control · obesity −health behaviors smoking, sexual...

Documents