9) Population Based Screening Flashcards

1
Q

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

A

Spontaneous presentation
Opportunistic case finding
Screening

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2
Q

What is the purpose of screening?

A

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

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3
Q

What is screening?

A

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

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4
Q

What is a diagnosis?

A

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

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5
Q

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

A
Condition
Test
Intervention 
Programme
Implementation
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6
Q

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

A

Important health problem that is well understood

All cost effective primary prevention intervention implemented

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7
Q

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

A

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

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8
Q

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

A

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

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9
Q

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

A

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

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10
Q

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

A

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

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11
Q

What is a false positive in screening?

A

Refer well people for further investigation

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12
Q

What are the implications of false positives?

A

Stress, inconvenience and costs

Lower uptake of screening In future

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13
Q

What is a false negative in screening?

A

Failure to refer those who have an early form of disease

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14
Q

What are the implications of false negatives?

A

Inappropriate reassurance and delayed presentation

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15
Q

What is sensitivity?

A

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

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16
Q

What is specificity?

A

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
Q

What is the positive predictive value?

A

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

18
Q

What is the negative predictive value?

A

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

19
Q

Why is evaluation required on screening programmes?

A

Programmes must be base on good quality evidence

Great pressure to start screening programmes

20
Q

What is lead time bias?

A

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

21
Q

What is length time bias?

A

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

22
Q

What is selection bias, in reference to screening?

A

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

23
Q

Give some sociological critiques of screening:

A

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