What is the primary objective of screening?
Detection of a disease in its early stages in order to treat it and deter its progression
What is the secondary objective of screening?
Reduce cost of disease management by avoiding costly interventions required at later stages
What are the 3 types of screening?
- Mass
- Selective
- Periodic
What is mass screening?
- Applied to an entire population
- Ex. cholesterol screening at a health fair
What is selective screening?
- Targeted
- Performed for specific high-risk populations
- Ex. TB tests for hospital employees
What is periodic screening?
- Screen a discrete, but well, subgroup of the population on a regular basis over time for predictable risks or problems
- Ex. cervical cancer
What are advantages of screening?
- Simplicity (for some)
- Target individuals or groups
- Options of one-test or multiple-test
- Opportunity for health education
What are disadvantages of screening?
- Not 100% accurate
- Will have false positives and false negatives
What are implications of false positive?
- Undo worry
- Stigma
- More invasive testing
- Unnecessary treatment
What are implications of false negative?
- May lose opportunity for early intervention
- May engage in risky behavior due to negative status
How do we select a screenable disease?
- Significance: is this a true concern? Level of threat?
- Detection: Can we screen for it? Do we have the technology?
- Should screening be done: What does evidence say and what is the benefit of knowing?
What is sensitivity?
- The ability of a test to correctly identify people who have the condition being tested for
- Identify true positives
- Poor sensitivity = increased false negatives
What is specificity?
- The ability of a test to correctly identify people who do not have the condition being tested for
- Identify true negatives
- Poor specificity = increased false positives
What is the equation for sensitivity?
TP/(TP+FN)
What is the equation for specificity?
TN/(TN+FP)
Who are the people with the disease who test +?
True positive
Who are the people with the disease who test -?
False negative
Who are the people without the disease who test +?
False positive
Who are the people without the disease who test -?
True negative
