Preventative Medicine (7 & 8) Flashcards
Primary prevention
Preventing the onset of disease - behaviour and environment (vaccine)
Secondary prevention
Halt progression once started, early diagnosis, screening NB healthy people thus different
Tertiary prevention
Limit disability and complications in established disease - rehabilitation
Geoffrey Rose’s single population theory
- primary determinants of disease are mainly economic and social therefore its remedies must be economic and social
- medicine and politics cannot and should not be kept apart
High risk
Identify and treat the ‘top end’ of the population distribution (screening in GP)
Population approach
Shift the mean of the entire distribution to the left (increase exercise, reduce salt in diet, reduce obesity)
Individual based approach
- Identify individuals at high risk - screening
- Intervene only in individuals at high risk
- Risk-benefit balance individually assessed
Population based approach
- Identify important risk factors for the community (prevalence)
- Policy to reduce risk irrespective of individual risk
- Risk-benefit balance for whole community
Derek Wanless
‘Securing our Future Health’ 2002, economic analysis showing burden of ill health on QoL in 2020
Sensitivity =
True positive/(True positive + False negative)
Specificity =
True negative/(False positive + True negative)
Sensitivity
The proportion of people with the disease who are identified as having it by testing positive
Specificity
The proportion of people without the disease who are correctly re-assured by a negative test result
Positive predictive value
Probability that a person with a positive test result actually has the disease
Negative predictive value
Probability that a person with a negative test result does not actually have the disease
High sensitivity
- Maximise identification of diseased people in the screened population
- Relatively few false negatives
- Unnecessary investigation/treatments for others
- Lots of false positives
High specificity
- Tend to detect only people with the disease
- Relatively few false positives
- Will miss people who have/at risk of disease
- Lots of false negatives
Desire high sensitivity
- Adverse consequences of late treatment worse
- Adverse consequences of missed diagnosis for society
- Diagnosis confirmed by other tests/correct diagnosis before treatment
Desire high specificity
- Diagnosis is associated with anxiety/stigma
- Further investigations are time-consuming, painful/expensive
- Cases are likely to be detected by others means before it’s too late
- Treatment offered without further investigation
Lead time bias
Early diagnosis falsely appears to prolong survival
Length time bias
Screening over-represents less aggressive disease
Wilson and Jungner
10 principles and practice of screening for disease
