Prevention and screening Flashcards
What criteria used for screening?
Wilson and Jungner criteria
Types of prevention and example of each?
Primary - Prevent onset of disease (exercise more, eat well)
Secondary - Early identification of disease and prevent disease from worsening (QRisk and statin administration)
Tertiary - Rehab following significant illness (medication post-MI +/- PCI)
What is the definition of screening?
A process which sorts out apparently well people who probably have a disease from those who probably do not.
Types of screening?
Population-based screening programmes Opportunistic screening Screening for communicable diseases Pre-employment and occupational medicals Commercially provided screening
What are some of the Wilson and jungner criteria?
The condition:
Important health problem
Latent / preclinical phase
Natural history known
The screening test:
Suitable
Acceptable
The treatment:
Effective
Agreed policy on who to treat
The organisation and costs:
Facilities
Costs and benefits
Ongoing process
Define sensitivity
the proportion of people with the disease who are
correctly identified by the screening test
Sensitivity = No. of true positives/(no. of true positives + false negatives)
High sensitivity ideal for contact tracing purposes in a pandemic
Define specificity
the proportion of people without the disease who are
correctly excluded by the screening test
Specificity= No. of true negatives/(no. of true negatives+ false positives)
Define positive predictive value
the proportion of people with a positive test
result who actually have the disease
Define negative predictive value
the proportion of people with a negative
test result who do not have the disease
Difference between predictive values and sensitivity/specificity?
Predictive values based on underlying prevalence. Sensitivity and specificity are not.
Type of bias in screening?
Lead-time bias (Screened patients have same survival rate as those not screened)
Length-time bias (less aggressive cancers more likely to be picked up from screening compared to more aggressive cancers –> hence die later)