Screening Flashcards
What is screening?
A process of identifying seemingly healthy individuals who may be at increased risk of a disease
What is Screening’s main purpose?
Prevention
What is primary prevention?
Preventing a disease/condition from occurring in the first place, eliminating risk factors that contribute to the disease
What is secondary prevention?
Detecting a disease ASAP to alter course and improve health outcomes
What is tertiary prevention?
Trying to slow down progression of a disease, and help people to manage illness effectively
Define sensitivity
Proportion of people with disease correctly identified (a/a+c)
Define specificity?
Proportion of people without disease correctly excluded (d/b+d) [How well test detects those without a disease]
What is the positive predictive value?
Proportion of people with +ve result who have disease (a/a+b)
What is negative predictive value?
Proportion of people with -ve result who don’t have disease (d/c+d)
What is prevalence?
Proportion of people found to have a disease at a point in time
What is incidence?
Rate at which new cases occur in population in certain time period
What is Wilson and Jungner criteria used for?
Determine if condition should be screened for
What are the 10 WJ criteria?
1) Condition should be serious health problem
2) Natural history of condition should be understood
3) Should be detectable early stage
4) Treatment should be available
5) Facilities for diagnosis/treatment should be available
6) Should be a suitable test
7) Test should be acceptance to population’
8) Agreed policy on whom to treat
9) Cost should be balanced against benefits
10) Should be a continuous process, rather than one off
Describe screening selection bias
People who choose to participate may be different from those that don’t (Can’t have proper randomisation)
What is length-time bias?
Diseases with longer period of presentation more likely to be detected
