Monitoring the Incidence of Disease

1
Injury Surveillance
Thomas Songer, PhD University of Pittsburgh
2
Why should we be concerned with monitoring
injuries?
3
Definitions
Prevention

• Reducing the incidence of disease
• Reducing the prevalence of disease

Control

• Ongoing programs aimed at reducing the incidence
  or prevalence of disease

Last, Dictionary of Epidemiology
4
Public Health Approach to Injury Control and
Prevention

• Define the Magnitude of the Problem
• Identify associated causes and risk factors
• Design and Implement the Intervention
• Evaluate the Intervention

5
Epidemiology is a Science of Rates

• death rates
• disability rates
• hospitalization rates
• incidence rates
• prevalence rates

numerator
denominator
6
Injury Deaths, Australia, 1992
Harrison, 1995
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Injury Death Rates, Australia, 1992
Harrison, 1995
8
How do we identify injuries?
9
Approaches Towards Monitoring Injury in the
Population

• Death Certificates
• Population Surveys
• Surveillance
• Registries
• Capture-Recapture

10
Government Surveys

• National Health Interview Survey
• National Hospital Ambulatory Care Survey
• National Hospital Discharge Survey
• Behavioural Risk Factor Survey and Surveillance

Provide a better picture of the health status of
the population
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Surveillance

• Systematic, regular ascertainment of incidence
  using methods distinguished by their
  practicality, uniformity, and frequently their
  rapidity, rather than by complete accuracy.

Last, 1990
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Types of Surveillance

• Active
• Passive

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Active Surveillance

• the collection of data on a disease by regular
  outreach. Designated medical personnel are
  called at regular intervals to collect
  information on the new cases of disease.

monitoring domestic violence in emergency
departments
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Passive Surveillance

• data generated without contact by the agency
  carrying out the surveillance. Reportable
  diseases fall under this type of surveillance.

spinal cord injuries
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Sentinel Events

• An event(s) that can be used to assess the
  stability or change in the health of a population.

John Last Dictionary of Epidemiology
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Registry

• A file of data concerning all cases of a
  particular disease or other health-relevant
  condition in a defined population such that the
  cases can be related to a population base.

Last, Dictionary of Epidemiology
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Where do the data for the numerator and
denominator come from in injury surveillance?
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EMS
Police
Self-Treat
Emergency Dept.
doctor
Injury
Hospital
Morgue
Trauma Center
Rehab Center
Robertson, 1992
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• The monitoring of incidence unfortunately is more
  complicated than the monitoring of mortality,
  because incidence data are hard to come by,
  registration of cases is even now seldom
  complete, and increases in the recorded rates may
  be due to an increase in the efficiency of
  registration.

Sir Richard Doll, 1990
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Numerator Issues
?

• Definition
• Ascertainment
• Severity

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ICD-9 Codes

• N Codes - Nature of injury, anatomy
• E-Codes - External cause of injury

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E-codes

• Are often missing on medical records
• Some states now require their use in ED and
  Hospital Admission records
• Important for identifying cause of injury and
  designing control programs
• Help to assign intent

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Sources for Monitoring Injuries
Woodland Hills School District
4 month
1 month
recall
student recall
medical
excuses
attendance
records
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Percent ascertainment for each of the four
monitoring sources
90
80
70
60
50
40
30
20
10
0
1 month
medical
attendance
4 month
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Data Sources and Injury Severity
No injury Mild Moderate Severe
Fatal

• Survey
• Doctor visit
• Hospital adm.
• Trauma ctr.
• Death cert.

Rogams, 1995
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Denominator Issues

• Population Base
• Which Denominator?

?
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What is the crash risk related
to older drivers? How important is this risk?
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Crash Involvement Rate
200
150
100
per 1000 licensed drivers
50
0
16
20
25
30
35
40
45
50
55
60
65
70
75
80
85
Age
NHTSA, FHWA
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Involvement Rate by Mileage
2000
1500
per 100 million miles VMT
1000
500
0
16
20
25
30
35
40
45
50
55
60
65
70
75
80
85
Age
NHTSA, FHWA
30
Fatality Rate
12
10
8
6
per 100 million miles
4
2
0
16
20
25
30
35
40
45
50
55
60
65
70
75
80
85
Age
NHTSA, FHWA
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Limitations in Injury Surveillance

• Few standards or guidelines
• Lack of population-based data
• Inflexibility of data systems
• Inability to integrate data systems
• Important data elements are not collected

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A Minimum Basic Dataset for Unintentional Injuries

• Age, Gender, Ethnic Group
• Place of occurrence
• Date of Injury
• Outcome of Injury
• Location of Injury
• Activity when accident happened