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Question 1

Define screening

Answer 1

A systematic attempt to detect an unrecognised condition using tests, examinations which can be applied rapidly, cheaply. They are used to distinguish between apparently well people who probably have the disease or precursor and those who probably don’t.

Question 2

What happens after someone screens as positive?

Answer 2

They are at high risk of the disease and diagnostic tests are performed to determine if they have the disease or not

Question 3

What are the ways in which disease is detected?

Answer 3

1. Spontaneous presentation2. Opportunistic case finding3. Screening

Question 4

What are the criteria for the disease so that it can be screened for?

Answer 4

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

Question 5

What are the criteria for the test for screening?

Answer 5

• is simple and safe- is precise and valid- is acceptable to the population- distribution of test values in the population must be known (proportion of people who test positive and negative)- an agreed cut-off level must be defined- there must be an agree policy on who to test further

Question 6

What are the criteria for the treatment for the disease to be screened?

Answer 6

• need effective evidence based treatment- early treatment must be advantageous and not just bring forward the date of diagnosis- need to have an agreed policy on who to treat

Question 7

Give some criteria of the programme that must be considered

Answer 7

• need to consider other options- benefits should outweigh physical and psychological harm- need to have sufficient facilities for diagnosis and treatment

Question 8

What are false positives?

Answer 8

Occurs when the programme refers healthy people for further investigation and they undergo invasive diagnostic testing when they do not have the condition

Question 9

What are false negatives?

Answer 9

When there is a failure to refer people who do actually have the disease which gives false reassurance for patients.

Question 10

Define sensitivity

Answer 10

The proportion of people who have the disease who test positive. The probability that a case will test positive. Also known as the detection rate.

Question 11

Define specificity

Answer 11

The proportion of people who do not have the disease who test negative. The probability that a non-case will test negative.

Question 12

Define positive predictive value

Answer 12

The probability that someone who has tested positive actually has the disease.

Question 13

What is the PPV influenced by?

Answer 13

The prevalence of the disease - a higher prevalence condition has a higher PPV than a lower prevalence condition.

Question 14

What is the relevance of PPV?

Answer 14

You will only screen in a high prevalence population

Question 15

What is a negative predictive value?

Answer 15

Proportion of people who test negative and actually do not have the disease

Question 16

Give some advantages of screening

Answer 16

1. Early detection of a disease may improve the outcome2. True negative reassure patients

Question 17

Give some disadvantages of screening

Answer 17

1. False positives expose patients to invasive diagnostic tests2. False negative falsely reassure patients3. False negative do not get diagnostics tests they may benefit from4. Expensive interventions divert money away from treatment5. People who get false positives are less likely to take part in screening in the future

Question 18

What is lead time bias?

Answer 18

Screened patients appear to survive longer but this is only because they were diagnosed earlier. They live the same amount of time but know that they have the disease for longer which can have an impact on quality of life.

Question 19

What is length time bias?

Answer 19

Disease that are detectable through screening are more likely to have a favourable prognosis and may have never caused a problem

Question 20

What disease is screening more likely to pick up?

Answer 20

Slow growing, unthreatening cases compared to fast growing, aggressive ones

Question 21

Define selection bias in screening

Answer 21

People who engage in screening are more likely to engage in other health behaviours that protect them from disease

Question 22

How is the doctor-patient relationship changed?

Answer 22

Normally the patient presents to the doctor. With screening, the doctor approaches the patient who may or may not have the disease

Question 23

Give some limitations of screening programmes

Answer 23

They are very complex – defining cut-off points for people to screen, what is abnormal, who goes for further tests. Diagnostic tests can be very invasive and more often than not, people are referred for unnecessary tests.

Question 24

Give some examples of screening programmes

Answer 24

Abdominal Aortic AneurysmBowel cancerBreast cancerCervical cancerDiabetic RetinopathyDown’s syndromeFoetal anomaliesPKUSickle Cell and Thalassaemia

Question 25

What are the four critiques of health promotion and screening?

Answer 25

Structural critiquesSurveillance critiquesSocial Constructionist critiqueFeminist critique

Question 26

Describe the structural critiques

Answer 26

Victim blaming- individuals are encouraged to take responsibility for their own health- is everyone equally able to do this?Individualising pathology- need to address the underlying causes of disease

Question 27

Describe surveillance critiques

Answer 27

Individuals and populations and becoming more and more a subject of surveillance- is prevention a wider apparatus of social control?

Question 28

Describe social constructionist critiques

Answer 28

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

Question 29

Describe the feminist critique

Answer 29

Is screening targeted more at women than men?