Uses and Abuses of Screening Tests

1
Uses and Abuses of Screening Tests

• Screening tests are ubiquitous in practice
• Principles of screening are widely misunderstood
• Goal of screening is to test apparently well
  people to find those at increased risk of a
  disease or disorder
• Inappropriate screening is harmful
• Injurious to ones health
• Stigmatizing
• Costly

2
Differences between Clinical and Screening Tests

• Screening Tests
• Provider Initiated
• Healthy patient
• Patient not seeking help
• If patient initiated, then can be costly and of
  no clinical value

• Clinical Tests
• Patient Initiated
• Patient with a complaint
• Risk and cost acceptable to the patient

3
When Earlier Diagnosis is Worth the Cost

• If improves survival or quality of life
• If the clinician has the time to manage the Dx
  before Sx develop
• If the patient with an earlier Dx will comply
  with intervention
• If the screening program effectiveness has been
  established
• If the test cost, accuracy and acceptibility are
  acceptable to the patient and society
• (Sackett, Clinical Epidemiology a basic science
  for clinical medicine)

4
Questions Clinicians Should Ask Themselves Before
Screening a Patient

• What are the potential harms of screening?
• What right do clinicians have to rob people of
  their perceived health, and for what gain?
• If a test is available, should it be used?
• Is the test valid?
• Where should the cut-off for abnormal be?
• Can test results be trusted?
• Should a follow-up test be done?
• Does the screening test really improve health?
• (Grimes, Lancet 2002)

5
Criteria Needed for a Screening Program

• Disease
• medically important and clearly defined
• prevalence known
• effective intervention exists
• Policy
• cost-effective
• facilities for Dx and Rx available
• course of action is generally agreed upon and
  acceptable
• Tests
• safe, valid, and reliable
• reasonable cut-off level defined
• (Cuckle, Principles of screening. In Antenatal
  and neonatal screening)