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Screening. Sherine Shawky, MD, Dr.PH Assistant Professor Public Health King Abdulaziz University College of Medicine shshawky@hotmail.com. Epidemiology in Medicine. Foundation of medical research Support for medical advancement Essential in medical education & practice

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screening

Screening

Sherine Shawky, MD, Dr.PH

Assistant Professor Public Health

King Abdulaziz University College of Medicine

shshawky@hotmail.com

epidemiology in medicine
Epidemiology in Medicine
  • Foundation of medical research
  • Support for medical advancement
  • Essential in medical education & practice
  • Boundary for biostatistics
learning objectives
Learning Objectives
  • Understand the concept of screening
  • Understand the characteristics of health-related events suitable for screening
  • Recognize the characteristics of a screening program
performance objectives
Performance Objectives
  • Apply screening for early detection of risk factors & diseases
  • Identify the factors suitable for screening
  • Evaluate the benefit of screening
screening5

Screening

Screening is the process to detect among healthy people disorders or risk factors of which they are unaware

flow diagram for a screening program
Flow diagram for a screening program

Population

Screening test

Test -ve

Test +ve

Diagnostic procedures

Unaffected

Affected

Re-screen

Intervention

Re-screen

types of screening
Types of screening
  • Mass
  • Multiple or multiphasic
  • Targeted
  • Case-finding or opportunistic
factors appropriate for screening
Factors appropriate for screening
  • Important health problem
  • High prevalence
  • Natural history understood
  • Long latent period
  • Early detection improves prognosis
evaluation of a screening program
Evaluation ofa screening program
  • Reliability
  • Feasibility
  • Validity
  • Performance
  • Effectiveness
reliability
Reliability
  • Biological variation
  • Program method
  • Intraobserver variability
  • Interobserver variability
feasibility
Acceptability

Quick

Easy

Safe

Cost effectiveness

Screening

Diagnosis

Follow-up

Intervention

Feasibility
validity
Validity
  • Sensitivity:

Probability to test positive among truly affected

  • Specificity:

Probability to test negative among truly unaffected

performance
Performance
  • PV+:- Probability to be affected among test positives
  • PV-:- Probability to be unaffected among test negatives
  • PCC:- Probability to be correctly classified
effectiveness
Effectiveness
  • Outcome measures:
    • Morbidity
    • Disability
    • Mortality
effectiveness15
Effectiveness
  • Bias
    • Patient self-selection
    • Lead time
    • Length
study designs for screening 1 correlation studies
Study designs for screening 1. Correlation Studies
  • Use:

Description of population

  • Strength:

Suggest possibility of benefit

  • Limitation:

Can’t test hypothesis

study designs for screening 2 analytical studies
Types:

Case-control

Cohorts

Use:

Comparison of rates

Advantage:

Test hypothesis

Limitation:

Selection

Lead time

length

Study designs for screening 2. Analytical Studies
study designs for screening 3 randomized trials
Study designs for screening 3. Randomized Trials
  • Use:

Comparison of rates

  • Strength:

Most valid test of hypothesis

  • Limitation:

Cost, ethics & feasibility

evaluation of screening
Evaluation of screening

*Sensitivity= TP/TA *PV+ = TP/SP

*Specificity= TN/TH *PV-= TN/SN

*PCC= TP+TN/GT

conclusion
Conclusion
  • Objectives of screening
    • Reduce disease incidence
    • Reduce morbidity, disability & mortality
  • Criteria for screening
    • Appropriate factor
    • Beneficial program
review questions developed by the supercourse team
Review Questions (Developed by the Supercourse team)
  • What is screening and what types of screening can you name?
  • What are the objectives of screening?
  • For what type of diseases would it be appropriate to set up screening programs? List characteristics.
  • How is screening program evaluated?