Session 6 - Screening

Question 1

Define screening

Answer 1

Screening is a systematic attempt to diagnose a previously unrecognised condition by the application of tests, examinations or other methods in a rapid, cheap way in order to distinguish between people who have the disease (or its precursor) and those who do not.

Question 2

Give three different methods of detection of disease`

Answer 2

Spontaneous presentation
Opportunistic case finding
Screening

Question 3

Outline the path of a positive screen result

Answer 3

Screen -> Positive screen -> Diagnostic tests -> Disease/no disease

Question 4

Give four overall criteria which must be fulfilled before screening implemented

Answer 4

Disease
The test
Treatment
Programme

Question 5

Give four points concerning disease which must be fulfilled before screening

Answer 5

Must be an important health problem
Epidemiology and natural history must be well understood
Must have an early detectable stage
Cost-effective primary interventions must have been considered and implemented

Question 6

Give 6 points concerning the test which must be implemented before screening

Answer 6

Simple and safe
Valid and precise
Acceptable to the population
Distribution of test values must be know
Agreed cut off level for positive 
Agreed policy on who to follow up further

Question 7

Give three treatments criteria

Answer 7

Effective evidence based treatment must be available
Early treatment must be advantageous
Agreed policy on whom to treat

Question 8

Give three programme criteria

Answer 8

Other options considered
Benefit shoudl outweigh physical/psychological harm
Facilities for diagnosis and treatment

Question 9

What is a false positive

Answer 9

Screening programme refers well people for further investigation
Offered diagnostic testig for a condition they do not actually have

Question 10

What is a false negative

Answer 10

Failure to refer people who do actually have disease

False reassurance for patients

Question 11

What is sensitivity?

Answer 11

Draw out table
Proportion of people with disease who test positive
a/a+c

Question 12

What is specificity?

Answer 12

The proportion of people without the disease who are test negative
d/b+d

Question 13

What is PPV?

Answer 13

Positive predictive value
The probability that someone who has tested positive actually has the disease
a/a+b

Question 14

What is a stong influencer of PPV?

Answer 14

Prevalence of disease

“If I test positive, does that mean I definitely have the disease?”

Question 15

Can two tests have different PPV and same sens and spec?

Answer 15

Yes

Question 16

What is negative predictive value?

Answer 16

Proportion of peoplee who are test negative who actually do not have the disease
d/c+d

Question 17

Give two advantages of screening

Answer 17

Early detection of disease may improve outcome

Reassurance for those who test negative

Question 18

Give four disadvantages of screening

Answer 18

False positive - Uneccesary tests
False negatives - False reassurance
False negative - Not offered dianositc testing they may benefit from
Expensive intervention that divert money from testing

Question 19

What is lead time bias?

Answer 19

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

Question 20

What is length time bias

Answer 20

o Screening programmes are better at picking up slow-growing, unthreatening cases than aggressive, fast-growing ones
o Diseases that are detectable through screening are more likely to have favourable prognosis, and may indeed never have caused a problem
 Curing people that don’t need curing?

Question 21

What is selection bnias?

Answer 21

o Those who have regular screening are also likely to engage in other health behaviours that protect them from disease
o Similar to ‘healthy worker’ bias
o A RCT would help deal with this bias

Question 22

Give three criticisms of screening programmes

Answer 22

Alteration of usual doctor-patient contract
Complexity of screening programmes
Limitations of screening (harm caused)

Question 23

Give four examples of screening in UK

Answer 23

o	Abdominal Aortic Aneurysm
o	Bowel cancer
o	Breast cancer
o	Cervical cancer
o	Diabetic Retinopathy
o	Down’s syndrome
o	Foetal anomalies
o	PKU
o	Sickle Cell and Thalassaemia

Question 24

Give four categories of sociological critiques for screening

Answer 24

Structural critiques
Surveillance critiques
Social constructionist
Feminist critique

Question 25

Give two structural critiques

Answer 25

o Victim blaming
 Individuals encouraged to take responsibility for their own health
 Are all equally able to do this?
o Individualising pathology
 What about addressing underlying material causes of disease?

Question 26

Give a surveillance critique

Answer 26

o Individuals and populations increasingly subject to surveillance
o Prevention part of wider apparatus of social control?

Question 27

Give a social constructionist critique

Answer 27

o Health and illness practices can be seen as moral – given meaning through particular social relationships

Question 28

Give a feminist critique

Answer 28

Is screening targeted more at women?