Public health Flashcards
What are the 3 types of prevention?
- Primary: stopping disease from occurring e.g. vaccines
- Secondary: detecting a disease early e.g. screening
- Stopping disease from progressing e.g. diabetic foot care, stroke rehab
What is the preventative paradox?
A preventative measure which brings much benefit to the population often offers little to each participating individual.
I.e. it’s about screening a large number of people to help a small number of people.
What does sensitivity mean?
the proportion of people with the disease who are correctly identified by the screening test.
What does specificity mean?
the proportion of people without the disease who are correctly excluded by the screening test.
PPV vs NPV?
PPV: the proportion with a positive test result who actually have the disease.
NPV: the proportion with a negative test result who do not have the disease.
What is the wilson + jugner criteria for screening?
- The condition should be an important health problem
- Treatment should be available
- Facilities for diagnosis and treatment should be available
- There should be a recognisable latent or early symptomatic stage
- There should be a suitable test or examination
- The test should be acceptable to the population
- The natural history of this condition should be understood
- There should be a policy on whom to treat as patients
- Costs of screening should be economically balanced
- Screening should be a continuous project, not just one off
Lead time bias vs length time bias?
Lead time : early detection results in an apparent increase in survival time
Length time: differences in the length of time taken for a condition to progress to severe effects that may affect the apparent efficacy e.g. less aggressive cancers that slowly progress are more likely to be spotted
What are the prospective studies vs retrospective studies?
Prospective: cohort/RCT
Retrospective: Case control/cross-sectional/case series/case report
Incidence vs prevalence?
Incidence – the number of new cases of a disease that develop in a population (e.g. per 100,000) in a given time frame (e.g. per year).
Prevalence – the total number of people in a population found to have a disease at a point in time.
Number of existing cases/population/points in time.
What is absolute risk?
gives a feel for actual numbers involved i.e. it has units.
E.g. deaths/1000 population.
What is relative risk?
ratio of risk of disease in the exposed to the risk in the unexposed i.e. no units.
Incidence in exposed ÷ incidence in unexposed.
Tells us about the strength of association between a risk factor + a disease.
What is attributable risk?
the rate of disease in the exposed that may be attributed to the exposure.
Incidence in exposed – incidence in unexposed
What is relative risk reduction?
the reduction in rate of the outcome in the intervention group relative to the control group.
(Incidence in unexposed – Incidence in exposed) ÷ incidence in unexposed.
What is absolute risk reduction?
the absolute difference in the rates of events between the 2 groups. Gives an indication of the baseline risk + the intervention effect.
Incidence in unexposed – incidence in exposed
What is odds and odds ratio?
The odds of an event is the ratio of the probability of an occurrence compared to the probability of a non-occurrence.
Odds = probability ÷ (1 – probability).
Odds ratio – the ratio of odds for the exposed group to the odds for the non-exposed groups.