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Flashcards in 9) Population Based Screening Deck (23):
1

What are the different way in which disease can be detected?

Spontaneous presentation
Opportunistic case finding
Screening

2

What is the purpose of screening?

Give a better outcome compared with finding something in usual way, due to intervening earlier

3

What is screening?

Systematic attempt to detect an unrecognised condition by tests, examination and/or other procedures

4

What is a diagnosis?

Identification of a suspected disease through tests, examination and/or other procedures

5

What are the criteria that need to be considered for a screening programme?

Condition
Test
Intervention
Programme
Implementation

6

In terms of the condition, what things need to be considered if there is to be a new screening programme?

Important health problem that is well understood
All cost effective primary prevention intervention implemented

7

In terms of the test, what things need to be considered if there is to be a new screening programme?

Simple, safe, precise and validated
Cut off levels defined, test values in pop. known
Acceptable
Agreed policy on further diagnostic investigation to those that test positive

8

In terms of the intervention provided, what things need to be considered if there is to be a new screening programme?

Evidence that intervention at pre-symptomatic phase leads to better outcomes
Agreed policies on which people and what intervention should be offered

9

In terms of the programme itself, what things need to be considered if there is to be a new screening programme?

Effectiveness in reducing mortality
Clinically, socially and ethically acceptable
Benefit gained should outweigh harms

10

In terms of the implementation, what things need to be considered if there is to be a new screening programme?

Patient outcomes optimised
All other options for managing condition considered
Informed choice to potential participants
Quality assurance

11

What is a false positive in screening?

Refer well people for further investigation

12

What are the implications of false positives?

Stress, inconvenience and costs
Lower uptake of screening In future

13

What is a false negative in screening?

Failure to refer those who have an early form of disease

14

What are the implications of false negatives?

Inappropriate reassurance and delayed presentation

15

What is sensitivity?

Detection rate, proportion of people with the disease that test positive (a/a+c)

16

What is specificity?

Proportion of people who don't have the disease who are correctly identified by the test as not having the disease (d/b+d)

17

What is the positive predictive value?

Probability that someone who is tested positive actually has the disease (a/a+b)

18

What is the negative predictive value?

Proportion of people who are test negative who actually don't have the disease (d/c+d)

19

Why is evaluation required on screening programmes?

Programmes must be base on good quality evidence
Great pressure to start screening programmes

20

What is lead time bias?

Screened patients appear to survive longer but only because they were diagnosed earlier

21

What is length time bias?

Programmes better at picking up slow growing cases rather than aggressive, fast-growing ones, so screened diseases have favourable prognosis

22

What is selection bias, in reference to screening?

'Healthy volunteer' effect - those who are regularly screened likely to do other things that protect them from disease

23

Give some sociological critiques of screening:

Victim blaming
Population increasingly subject to surveillance
Moral obligation
Financial incentives for GPs to put patient in for screening