Asthma Screening and Case Detection

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Asthma Screening and Case Detection

• Leslie P. Boss MPH, PhD
• Centers for Disease Control and Prevention
• National Center for Environmental Health

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Clinical Screening

• the assessment of pre-clinical disease in
  individual patients by a clinician using special
  tests or standardized examinations in order to
  identify individuals needing special intervention.

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Population Screening

• the presumptive identification of unrecognized
  disease or defect by the application of tests,
  examinations, or other procedures which can be
  applied rapidly to sort out apparently well
  persons who probably have a disease from those
  who probably do not.

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Natural History of Disease
X
X
Screened
Death
X
X
Not Screened
Death
Disease Screen / Dx with
signs/ begins Diagnosis
symptoms
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Population Case Detection

• the presumptive identification of persons with
  unrecognized or undiagnosed disease by the
  application of tests, examinations, and other
  procedures that can be applied rapidly to sort
  out persons who have symptoms from those who do
  not.

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Case identification
Disease Symptoms Diagnosis
Predefined process occur occurs
endpoint begins
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1
2
4
Case detection
Screening
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A Good Screening Test

• Valid provides a good preliminary indication of
  which individuals actually have the disease and
  those who do not.
• Reliable gives consistent results when the test
  is performed more than once on the same
  individual under the same conditions.
• Sufficient yield amount of previously
  unrecognized disease which is diagnosed and
  brought to treatment as a result of the screening.

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Attributes of a Good Screening Test

• Simple
• Rapid
• Inexpensive
• Safe
• Acceptable

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WHO Screening Criteria (1)

• The condition must be an important health
  problem.
• The natural history of the disease should be
  understood.
• There should be a recognizable latent or early
  symptomatic stage.

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WHO Screening Criteria (2)

• There should be an accepted treatment.
• There should be an agreed upon policy about who
  to treat.
• Facilities for diagnosis and treatment should be
  available.
• There should be a suitable test or examination.

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WHO Screening Criteria (3)

• The test should be acceptable to the population.
• The cost of screening/case finding should be
  economically balanced in relation to other
  medical expenditures.
• Case finding should be a continuing process.

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Results of a Screening Test
Test results Disease State
Disease No
Disease Positive true positive
false positive Negative false negative
true negative
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Cost-Benefit of Screening
Benefit
QoL Measure

Treatment
Diagnosis

-
Cost
Periodic Continued Screening
-
Screening
Periodic Continued Screening
-
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Next Steps

• Continue research on the natural history of
  asthma.
• Understand the potential impact of screening
  programs on the health care infrastructure.
• Determine the cost and benefit of
  population-based screening (and case-detection)
  programs prior to implementation in communities.

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Next Steps (cont)

• Improve disease detection in the clinical
  setting.
• Assure quality disease management for all
  diagnosed patients.
• Use precise terminology regarding identification
  of people with asthma.
• Consolidate and disseminate existing research
  results on clinical screening and
  population-based case finding efforts.