Screening

Question 1

What are the three types of prevention?

Answer 1

Primary - preventing early disease, control risk factors
Secondary - preventing disease progression
Tertiary - preventing advanced disease with complications

Question 2

What is screening?

Answer 2

A means of secondary prevention

Question 3

How does WHO define screening?

Answer 3

The presumptive identification of unrecognised disease in an apparently healthy, examinations or other procedures that can applied rapidly and easily to the target population

Question 4

What does presumptive identification refer to?

Answer 4

Undertaken in people who are thought to be healthy

Question 5

What is the difference between screening and diagnosis?

Answer 5

Screening gives an indication of the chance that somebody has a disease.

Screening finds people at a higher chance of having the condition in question.

Diagnostic tests tell you whether the condition is actually present.

Question 6

What is the purpose of screening tests?

Answer 6

To reduce risk of adverse health outcomes in future

Question 7

What are the characteristics of screening tests?

Answer 7

Simple, acceptable and affordable - conducted on large numbers of people

Question 8

What do screening tests indicate?

Answer 8

Indicates the chance of having a disease, further testing is needed in case of abnormal findings

Question 9

What are the three types of screening?

Answer 9

Case finding
Targeted screening
Mass screening

Question 10

What is case finding?

Answer 10

When an individual goes to see a clinician for one reason and at the same time is checked for another

Question 11

What are the 7 steps of a screening pathway?

Answer 11

Identify the people to invite
Discuss and offer screening
Carry out screening test
Provide and discuss results/options
Carry out diagnostic/confirmatory test if required
Provide and discuss results/options
Offer advice/treatment

Question 12

Why are the Wilson-Jugnet criteria important?

Answer 12

Make sure screening is only implemented when beneficial

Question 13

What are the 4 themes covered in the Wilson-Jugner criteria?

Answer 13

Disease
Screening test
Diagnostic test and treatment
Overall screening programme

Question 14

What are the criteria related to disease?

Answer 14

Important health problem
Development from latent to declared disease understood
Recognisable early stage

Question 15

What are the criteria related to the screening test?

Answer 15

Suitable test that is safe, valid, cheap and reliable

Test should be acceptable to the population

Question 16

What are the criteria related to diagnostic testing and treatment?

Answer 16

Agreed policy on who to treat as patients
Should be accepted treatment for patients with recognised disease
Facilities for diagnosis and treatment should be available

Question 17

What are the criteria related to the overall screening programme?

Answer 17

Cost of case finding, diagnosis and treatment should be balanced with expenditure on medical care as a whole
Should be a continuous process not ‘once and for all’ project

Question 18

What is sensitivity?

Answer 18

Sensitivity is defined as the proportion of those with the disease who tested positive. This is also known as the true positive ‘rate’.

Question 19

What is specificity?

Answer 19

Specificity is defined as the proportion of those without the disease who tested negative. This is also known as the true negative rate.

Question 20

What is the denominator in sensitivity and specificity?

Answer 20

Disease state

Question 21

What is positive predictive value?

Answer 21

proportion of positive tests that correctly identified those with the disease.

aka

he probability that following a positive test result, an individual will truly have that disease

Question 22

What is negative predictive value?

Answer 22

proportion of negative tests that correctly identified those without the disease

aka

the probability that following a negative test result, an individual will truly not have the disease

Question 23

How do you calculate sensitivity?

Answer 23

True positives / (true positives + false negatives)

Question 24

How do you calculate specificity?

Answer 24

True negatives / (false positives + true negatives)

Question 25

How do you calculate PPV?

Answer 25

True positive/ (True positive + false positive)

Question 26

How do you calculate NPV?

Answer 26

NPV = True negative/ (True negative + false negative)

Question 27

When would a disease have a low PPV?

Answer 27

rare, even with a very sensitive and specific test

Question 28

What is call recall system?

Answer 28

Large database that identifies those eligible who are the invited to screen

Then told result

Question 29

Why are there biases in screening?

Answer 29

Those who attend screening are commonly older affluent women

Generally fairly healthy

Question 30

What is the self-selection bias?

Answer 30

More health conscious people take part in screening

Widens inequalities

Question 31

How can we improve screening uptake?

Answer 31

Leaflets in multiple languages
Outreach work
Mobile screening units

Question 32

Why is self-selection bias an issue?

Answer 32

Misrepresents the success of screening since anyway those who are screened are overall healthier than the unscreened population

Question 33

What is lead-time bias?

Answer 33

Survival time appears longer because diagnosis was done earlier (for instance, by screening), irrespective of whether the patient lived longer

Question 34

What is length time bias?

Answer 34

overestimation of survival duration due to the relative excess of cases detected that are asymptomatically slowly progressing, while fast progressing cases are detected after giving symptoms

Question 35

Why is screening difficult to access for some people?

Answer 35

No fixed address
Do not understand language
Cannot attend - travel cost, work commitments etc.
Transgender and non-brnary

Question 36

What is screened for in the UK?

Answer 36

AAA
Bowel cancer
Breast cancer
Cervical cancer
Diabetic eye
Fetal anomalies
Infectious disease in pregnancy
Newborn (hearing, blood)
Sickle Cell/Thalassaemia