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HaDSoc > 6: Screening > Flashcards

6: Screening Flashcards

1
Q

What is screening?

A
  • A systematic attempt to detect an unrecognised condition
  • Through application of tests, examination etc
  • Can be applied rapidly (and cheaply)
  • Distinguish between apparently well persons who probably have the disease, and those who probably do not
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2
Q

What are the three ways in which disease is detected?

A
  1. Spontaneous presentation - patient to doctor with symptoms
  2. Opportunistic case finding - presents with symptoms, doctor takes opportunity to look for other diseases
  3. Screening - label as screen positive, then diagnosis
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3
Q

What is diagnosis?

A

Definitive identification of a suspected disease.
Tests, exams, other procedures
Treatment will follow

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4
Q

What are the 4 areas of criteria for implementing a screening programme?

A

Disease/condition
Test
Treatment
Programme

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5
Q

Describe screening criteria concerning the disease/condition

A
  • Important health problem
  • Need to understand epidemiology and progression
  • Need an early detectable stage
  • Must have considered primary prevention measures
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6
Q

Describe screening criteria concerning the test

A
  • Simple and safe
  • Precise and valid
  • Acceptable to the population
  • Distribution of test values in the population must be known
  • Define agreed cut off for test positives
  • Agree who to test further
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7
Q

Describe screening criteria concerning the treatment

A
  • Must have effective evidence based treatment
  • Early treatment must be advantageous - don’t just bring forward diagnosis date
  • Agreed policy who to treat
  • Optimise clinical management before participation in programme
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8
Q

Describe screening criteria concerning the programme

A
  • Proven effectiveness - RCT data
  • Quality assurance for whole programme
  • Other options besides screening considered
  • Be able to justify parameters to the public
  • Benefits to outweigh physical and psych harm - offer counselling
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9
Q

What is the calculation for sensitivity?

A

True positive/true positive + false negative

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10
Q

What is the calculation for specificity?

A

True negative/ false positive + true negative

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11
Q

What is the calculation for PPV?

A

True positive/true positive + false positive

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12
Q

What is the calculation for NPV?

A

True negative/ false negative + true negative

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13
Q

What is sensitivity?

A

The detection rate - the proportion of people with the disease who test positive

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14
Q

What is specificity?

A

The proportion of people who do not have the disease who test negative

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15
Q

Do sensitivity and specificity ever vary?

A

No, they are functions of the test and should be the same in different populations

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16
Q

What is the positive predictive value?

A

The probability that someone who tested positive has the disease

17
Q

How is PPV influenced by prevalence?

A

If it is a high prevalence condition, the PPV will be high, so only screen in high prevalence populations

18
Q

What is the negative predictive value?

A

The proportion of people who test negative who do not have the disease

19
Q

What is prevalence? In terms of positives/negatives

A

True positives+ false negatives/whole population

20
Q

What are some advantages of screening?

A

Early detection may improve outcome

True negatives reassure patients

21
Q

What are some disadvantages of false positives?

A
  • Invasive diagnostic tests
  • Anxiety
  • May lead to lower uptake of future screening
  • Increased risk of interval cancer
  • Low PPV - many false positives
22
Q

What are some disadvantages of false negatives?

A
  • False reassurance
  • Not offered diagnostic tests from which they may benefit
  • Disease, although present, is not diagnosed
  • May present late - poor outcomes
23
Q

Name three difficulties in evaluating effectiveness of screening programmes

A
  • Lead time bias
  • Length time bias
  • Selection bias
24
Q

What is lead time bias?

A

Screen patients appear to survive longer, only because they were diagnosed earlier.
Patients live the same amount of time, but longer knowing they have the disease

25
Q

What is length time bias?

A

Screening is better at picking up slow growing, unthreatening cases than aggressive ones
Diseases detected by screening are more likely to have a good prognosis, may never have caused a problem.

26
Q

What is selection bias in relation to screening?

A

Skewed by the healthy volunteer effect. Those regularly screening are more likely to engage in health behaviours protecting them from disease. Similar to healthy worker bias - RCT would help deal with bias.

27
Q

Describe some critical perspectives on screening programmes

A

Alteration of the usual doctor-patient contract - usually sick patient presents to the doctor
Must be based on good quality evidence
Some are very complex -
Limitations include potential harm as well as benefit, can’t guarantee protection, increased emphasis on promoting informed choice.

28
Q

What are 4 sociological critiques of screening

A

Structuralist
Surveillance
Social constructionist
Feminist

29
Q

Describe structural critiques of screening?

A

Victim blaming - are all equally able to take responsibility for their own health
Individualising pathology - not addressing the underlying material cause

30
Q

Describe surveillance critiques of screening

A

Wider apparatus of social control

31
Q

Describe social constructionist critiques of screening

A

Health and illness practices can be seen as moral - screening seen as responsible. Obligation to go - not going is deviant and irresponsible

32
Q

Describe feminist critiques of screening

A

Is it more targeted at women than men?

33
Q

Give some examples of screening programmes in the UK

A
  • AAA –> all men USS >64 years old
  • Bowel cancer –> faecal occult blood –> colonoscopy (2 yearly, 60-69)
  • Breast cancer –> mammogram –> FNA (60-69, 2 yearly)
  • Cervical cancer
  • Down’s
  • PKU
34
Q

Describe the uptake of screening in lower socioeconomic groups

A
  • Less likely to attend screening
  • May have difficulty mobilising resources required to attend
  • May be more likely to have a negative definition of health –> manage as a series of crises, don’t see the need for preventative services.

HaDSoc (10 decks)

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