Screening

Question 1

Screening

Answer 1

investigating apparently healthy individuals to detect unrecognised disease/ precursors

Question 2

Why perform screening?

Answer 2

so measures can be taken to prevent/ delay development of disease/ improve prognosis.

Question 3

If earlier detection does not offer any hope of improved outcome

Answer 3

screening generally not indicated

Question 4

Screening may be used for risk factors

Answer 4

identify people at higher risk of developing disease where interventions will reduce risk

Question 5

Screening may also be used to identify people with infectious disease

Answer 5

Treatment/ control measures improve outcome for individual /prevent ongoing transmission

Question 6

How could screening do more harm than good?

Answer 6

false alarms,
inducing anxiety
treatment of early disease which would not otherwise have become a problem

Question 7

Ideal screening test

Answer 7

simple
safe
acceptable
inexpensive
repeatable 
valid (sensitive & specific).

Question 8

Screening tests are not the same as diagnostic tests

Answer 8

Aims to identify people with precursors/ at risk of condition.
Further diagnostic tests performed to confirm diagnosis

Question 9

Validity

Answer 9

ability to distinguish between subjects with condition & those without

Question 10

To assess validity of a screening test, true disease status of individuals must be known, usually through a definitive test which is referred to as

Answer 10

Gold Standard

Question 11

Sensitivity

Answer 11

Ability of test to correctly identify people with disease

Question 12

Sensitivity equation

Answer 12

Positive diseased / All diseased results

Question 13

Specificity

Answer 13

ability of test to correctly identify people without disease

Question 14

Specificity equation

Answer 14

Negative non diseased/ All non diseased results

Question 15

Positive predictive value (PPV)

Answer 15

likelihood that a patient with a positive test result will actually have the disease

Question 16

PPV Equation

Answer 16

Positive diseased/ All positive results

Question 17

Negative predictive value (NPV)

Answer 17

likelihood that a patient with a negative test result will not have the disease

Question 18

NPV Equation

Answer 18

Negative non diseased/ All negative results

Question 19

Receiver Operator Characteristics (ROC) curves

Answer 19

used to determine a cut- off value for a diagnostic or screening test

Question 20

Mass screening

Answer 20

Screening involving the whole population

Question 21

Targeted screening

Answer 21

Screening of selected groups who are anticipated to have an increased prevalence of the condition

Question 22

Systematic screening

Answer 22

People are called

Question 23

Opportunistic screening

Answer 23

Patient presents for another reason and are offered a test

Question 24

Major screening programmes in the UK

Answer 24

Antenatal
Neonatal 
Childhood
Cancers
Infections
Cardiovascular disease

Question 25

Evaluating screening programmes

Answer 25

Feasibility
Effectiveness
Cost

Question 26

Feasibility of screening

Answer 26

ease of organising population to attend
whether screening test is acceptable,
whether facilities and resources exist to carry out necessary diagnostic tests following screening.

Question 27

Effectiveness of screening

Answer 27

measuring extent to which implementing a screening programme affects subsequent outcomes

Question 28

Why is it difficult to measure effectiveness of screening?

Answer 28

Selection bias- those who participate
Lead time bias- screening identifies disease that would be identified at a later stage (apparent increased survival length)

Question 29

Why is cost of screening important?

Answer 29

Resources for health care are limited

Many competing demands for available money, health care professionals and facilities

Question 30

Ethics of screening must be considered

Answer 30

may be a risk attached to the screening test or subsequent diagnostic test

Question 31

Cancer screening UK

Answer 31

Cervical
Breast
Bowel

Question 32

2 rogue screening programmes UK

Answer 32

Abdominal aortic aneurysm

Diabetic eye screening