Rationale, principles, properties and risks of screening, and UK screening programmes

Question 1

Define screening?

Answer 1

Testing individuals who don’t think they have a health problem (asymptomatic) in order to allow early detection and treatment, and to provide information

Question 2

Give 2 rationale of screening for health conditions?

Answer 2

To allow early detection and treatment

To provide information so that the individual can make choices about their health

Question 3

Give 6 examples of NHS national screening programmes?

Answer 3

Cervical cancer
Breast cancer
Bowel cancer
Abdominal aortic aneurysms
Antenatal and neonatal testing
Diabetic eye disease

Question 4

In diabetic eye screening, what are the 3 early and 2 late progressive stages?

Answer 4

No retinal disease

Non-proliferative and proliferative retinopathy

Proliferative retinopathy and maculopathy

Late stages:
Visual loss
Blindness

Question 5

In diabetic eye disease screening, how is the diabetic retinopathy screened?

Answer 5

Take screening retina photos

Question 6

In diabetic eye disease screening, at what progressive stage is the individual referred to specialist for treatment, and why?

Answer 6

Referral and treatment at 3rd stage: proliferative retinopathy and maculopathy

If the diabetic eye disease progresses to late stages, individual could have vision loss then blindness

Question 7

What age range contains individuals eligible for a NHS health check?

Answer 7

Aged 40-74

Question 8

Which 5 conditions are individuals screened for at a NHS health check, to see if they are at higher risk?

Answer 8

Heart disease
Kidney disease
Diabetes
Stroke
Dementia (individual over 65 yrs)

Question 9

Give 5 examples of how conditions are screened for at NHS health checks?

Answer 9

HbA1c test
Bp test
Cholesterol test
BMI calculated
Asking about lifestyle eg. smoking habits

Question 10

In a NHS health check, if an individual has risk factors what is the next action?

Answer 10

Individual is referred to GP for risk factor management

Question 11

How does the National diabetes prevention programme screen for prediabetic/diabetic individuals?

Answer 11

Uses HbA1c/glucose test results from health check to identify individuals at risk of developing type 2 diabetes (prediabetic) or who are diabetic

Question 12

If the National diabetes prevention programme detects a prediabetic individual, how is this treated?

Answer 12

NHS can provide lifestyle advice and interventions

Question 13

If the National diabetes prevention programme detects a diabetic individual, how is this treated?

Answer 13

Individual is referred to GP

Question 14

How are individuals chosen to participate in a screening test?

Answer 14

Invitations and recalls are sent to individuals on the eligible register

Question 15

If an individual has confirmed diagnosis from screening and diagnostic testing, what is the next action?

Answer 15

Individual is referred for treatment or interventions, which aim to provide info and support

Question 16

In the screening phase of the screening process, what are the 3 possible outcomes?

Answer 16

positive, negative or uncertain screening test result

Question 17

Which individuals undergo diagnostic testing in the diagnostic phase of screening process?

Answer 17

Individuals with positive screening result

Question 18

In the diagnostic phase of the screening process, what are the 3 possible outcomes?

Answer 18

Abnormal findings (leads to confirmed diagnosis), negative diagnostic results or uncertain results

Question 19

Which individuals undergo intervention in the screening process?

Answer 19

Individuals with abnormal findings

Question 20

What are the 4 possible outcomes of intervention after screening process?

Answer 20

Better outcome due to early detection

Good outcome but early detection made no difference

Condition would not be affected so intervention was necessary

Poor outcome and early detection made no difference

Question 21

Give 4 risks of screening?

Answer 21

Over-diagnosis of conditions

False negative and false positive test results

Unnecessary intervention, due to screening not providing enough info on the progression of the individuals condition (might not warrant treatment) and false tests

Costs of intervention, further tests and treatment outweigh benefits

Question 22

Give 2 reasons why screening can lead to unnecessary intervention?

Answer 22

Screening not providing enough info on the progression of the individuals condition (might not warrant treatment)

False positive and negative tests

Question 23

Why are RCTs the ideal choice for providing evidence of screening test effectiveness?

Answer 23

They consider time trends in disease incidence and outcome compared to that in countries without screening tests

Question 24

Why are case control studies not the ideal choice for providing evidence of screening test effectiveness?

Answer 24

They consider screened individuals with disease and controls without disease to evaluate whether screening decreases number of disease cases

Inferior to RCTs as they are often have confounding bias

Question 25

What are 3 common sources of bias in screening test evaluation?

Answer 25

Healthy screening effect

Lead time bias

Length time bias

Question 26

What is meant by the healthy screening effect bias, in screening test evaluation?

Answer 26

Participants tend to be healthier than non-participants, so gives the appearance of more early detection

Question 27

What is meant by length time bias, in screening test evaluation?

Answer 27

Slowly-progressing diseases are more likely to be detected due to longer asymptomatic period, which have better prognosis and longer survival

Question 28

What is meant by lead time bias, in screening test evaluation?

Answer 28

Survival time falsely appears longer due to earlier detection, which makes screening tests seem more effective

Question 29

What 4 values are calculated to measure diagnostic accuracy of a screening test?

Answer 29

Sensitivity
Specificity
PPV
NPV