Screening

Question 1

What is screening ?

Answer 1

A process of identifying apparently healthy people who may be at increased risk of a disease or condition.

Question 2

If a person is found to be at increased risk of a disease/condition, what are some steps which can be taken ?

Answer 2

Offered information, further tests and appropriate treatment to reduce associated risks or complications.

Question 3

What are some of the main differences between screening and healthcare ?

Answer 3

Screening:

• mostly proactive
• targets asymptomatic patients
• implies benefit, but harms are always possible.

Healthcare:

• Patient initiated
• targets symptomatic patients
• possible hope or expectation but no promise of benefit

Question 4

Give 3 examples of screening programmes for each of adults, pregnant women, and infants.

Answer 4

Adults:
Bowel cancer
Cervical cancer
Beast cancer

Pregnant women:
Fetal anomaly
Infectious diseases
Sick cell and thalassemia

Newborn and Infants:
Physical examination
Blood spot
Hearing

Question 5

Describe the age, M/F, and frequency of screening for bowel cancel and breast cancer.

Answer 5

Bowel Cancer:

• M and F
• 50-74
• Every 2 years

Breast Cancer:

• F
• 50-70
• Every 3 years

Question 6

What are the requirements for the screening of a condition to be viable and effective ?

Answer 6

• Response to a recognized need
• Objectives defined and evaluation planned at outset
• Defined target population
• Scientific evidence of effectiveness
• Programme should be comprehensive and integrated
• Quality assured, with systematic mitigation of risks
• Informed choice, confidentiality and respect for autonomy -Programme should promote equity and access to screening The overall benefits of screening should outweigh the harm

Question 7

What does sensitivity calculate in screening programmes ? What is for the formula for it ?

Answer 7

How well the test picks up having the disease

Sensitivity = (Number of results where disease detected in people with the disease / Number of people with the disease) x 100%

Question 8

What does specificity calculate in screening programmes ? What is for the formula for it ?

Answer 8

How well the test detects not having the disease

Specificity = (Number of ‘normal’ results where disease is not detected in people without the disease /
Number of people without the disease) x 100%

Question 9

What is the characteristic of a highly sensitive screening programme ?

Answer 9

Detects most of the disease

Very few false negatives

Question 10

What is the characteristic of a highly specific screening programme ?

Answer 10

Correctly detects no disease

Very few false positives

Question 11

What is a positive predictive value ?

Answer 11

“Probability that subjects with a positive screening test truly have the disease.”

Question 12

What is a negative predictive value ?

Answer 12

“Probability that subjects with a negative screening test truly don’t have the disease.”

Question 13

What is the formula for positive predictive value ?

Answer 13

(Number of people with the disease and a positive test result / Number of people with a positive test result) x 100%

Question 14

What is the formula for negative predictive value ?

Answer 14

(Number of people without the disease and a negative test result / Number of people with a negative test result) x 100%

Question 15

How are PPV and NPV affected by prevalence ?

Answer 15

“If we test in a high prevalence setting, it is more likely that persons who test positive truly have disease than if the test is performed in a population with low prevalence.”

Question 16

What are the potential benefits of screening ?

Answer 16

• Reduced disease incidence (increased QOL)
• Reduced disease mortality
• Earlier, less radical treatment (increased QOL)
• Cost-effective
• Overall population benefit
• Reducing risks of developing serious condition or its complication

Question 17

What are the potential harms of screening ?

Answer 17

• False reassurance
• Over-investigation and treatment
• Anxiety
• Longer period of morbidity with unaltered prognosis
• Harm from screening test
• Opportunity costs
• Increased health inequalities

Question 18

What is the purpose of the Marmot Review of the UK Breast Screening Programme ?

Answer 18

Weights the benefits (e.g. deaths prevented) and harms (e.g. overdiagnoses ) of breast screening

Question 19

What was the conclusion of the Marmot Review of the UK Breast Screening Programme ?

Answer 19

Significant benefits to the screening, so it should continue.
Communication about the benefits and harms with the women crucial.

Question 20

What pieces of information which must be given to the patient before he/she can give informed consent to a screening procedure ?

Answer 20

• Purpose
• Potential risks and burdens
• Pathway following test results

Question 21

What are some examples of biases in screening programmes ?

Answer 21

• Participant (volunteer) bias
– “When the subjects who volunteer to participate in a research project are different in some ways from the general population”

• Lead-time bias
– “An apparent increase in survival due to detecting a health condition such as cancer at an early stage, when there is no actual effect on survival, just a longer period with the diagnosis”

• Length-time bias
– Detection of less aggressive forms of condition in screening (“increases apparent survival”)

Question 22

How can one measure the effectiveness of a screening ?

Answer 22

Randomised controlled trial
Time trend studies
Case control studies
Modelling studies

Question 23

Compare breast, cervical, and bowel cancer in terms of incidence and mortality for different deprivation levels.

Answer 23

Bowel Cancer: Higher incidence and mortality for more deprived levels

Cervical cancer: More incidence and mortality for more deprived levels

Breast cancer: Slightly more incidence for less deprived levels, same mortality

Question 24

Describe the potential impact of screening programmes on health inequalities ?

Answer 24

• Increased cost of treatment, social care etc

Question 25

Why are the inequalities created by screening programmes illegal ?

Answer 25

Equitable outcomes are a legal requirement of Equality Act

Question 26

With a = eligible population b = invited population

c = screened population, what is the formula for coverage ?

Answer 26

c/a x 100%

Question 27

What are some challenges with optimising coverage ?

Answer 27

• Minority ethnic groups
• Immigrants
• Travellers
• Prisoners
• Students
• Reduced uptake

Question 28

With a = eligible population b = invited population

c = screened population, what is the formula for uptake ?

Answer 28

c/b x 100%

Question 29

What are some challenges with optimising uptake ?

Answer 29

• Change of address
• Communication
• Health literacy
• Deprivation
• Accessibility
• Vulnerable groups

Question 30

What are some measures to improve screening engagement and uptake ?

Answer 30

• Promotion of screening programme
• Material in variety of languages
• “The wee C”
• “The Smear Amnesty”
• Toolkits for general practice

Question 31

What are some inequalities which exist in uptake of screening, in addition to inequalities in wealth ?

Answer 31

Learning disability, sex, minority ethnicity and age.

Question 32

What are some ways in which higher level of deprivation are affected by inequalities, regarding screening ?

Answer 32

Poorer outcomes, less lives saved, more treatment, reduced productivity (which threatens program viability)
As a result, less faith in the programme

Question 33

What are some measures to improve engagement in vulnerable groups ?

Answer 33

• Social marketing
• Qualitative research
• Known effective interventions
– Letter from GP; patient navigation; community mentors; “people like me”; languages; text reminders;
• Known barriers
– Uncertainty of benefit; fear of cancer; lack of time; disgust/ discomfort/embarrassment;