1
Q
What is screening?
A
Targets a specific population without symptoms
2
Q
How is screening different from health promotion activities?
A
Screening is proactive and acts as a filter
3
Q
What does the UK National Screening Committee oversee?
A
Population screening in the UK
4
Q
What is the aim of screening?
A
To intervene after disease development but before symptoms appear
5
Q
What are the six screening programmes in Scotland?
A
- AAA
- Bowel screening
- Breast screening
- Cervical screening
- Diabetic eye screening
- Pregnancy and newborn screening
6
Q
What are the classic screening criteria proposed by Wilson and Junger in 1968?
A
- Important health problem
- Accepted treatment available
- Long latent period
- Facilities for diagnosis and treatment
- Recognizable latent or early symptomatic stage
- Suitable test or examination
- Acceptable to the population
- Natural history understood
- Agreed policy on whom to treat
- Economically balanced cost
- Continuous process
7
Q
What are the criteria devised by NSC which build on Wilson and Junger?
A
- The condition:
* important problem
* Epi and natural history known
* Evidence of association between marker and disease
* Cost-effect primary interventions implemented as far as poss
2.The test
* Simple, safe, precise and validated
* Suitable cut off point identified
* Acceptable to target population
* Agreed policy on further diagnositic investigation - The intervention
* Effective intervention leading to better outcomes than usual care
* Evidence based policy on who to offer intervention to - The screening programme
* Evicence from high quality RCTs that screening is effective in reducing morbidity or mortality
* Information available for and understandable to patients to allow them to make informed choice
* Evidence that complete screening programme is clinically, socially and ethically acceptable
* Benefit should outweigh harm
* Opportunity cost should be economically balanced with expenditure on medical care as a whole - Implementation
* No more cost effective intervention could be introduced or current interventions increased
* Plan for managing and monitoring screening programme
* Adequate staffing and facilities for entire programme including treatment
* Public pressure for widening eligibility criteria should be anticipated and decisions on these parameters should be scientifically justifiable
8
Q
Define sensitivity in the context of screening tests.
A
Ability of the test to detect all those with disease in the screened population
9
Q
Define specificity in the context of screening tests.
A
Ability of the test to correctly identify those free of disease
10
Q
What is positive predictive value?
A
Probability of having the disease given a positive screening test result
11
Q
What is negative predictive value?
A
Probability of not having the disease given a negative screening test result
12
Q
What are the risks associated with false negatives?
A
- Misleading diagnosis
- Delayed diagnosis
- Increased morbidity and mortality
- Potential for risk-taking behaviour
13
Q
What are the risks associated with false positives?
A
- Misclassified diagnosis
- Unnecessary psychological consequences
- Unnecessary diagnostic tests or treatments
14
Q
What does a receiver operating curve (ROC) help assess?
A
- A plot of the trade-off between the sensitivity and specificity of a test across a range of threshold values (e.g different AAA diameters)
- Y axis is sensitivity and x axis is 1-specificity
- Dotted diagonal line represents a useless test with no discriminatory power
- The closer the curve is to left hand and top border, the better the test.
- AUC of 1 would be a perfect test
- Two main uses are: to aid in the setting of a threshold value for a test
- To compare the performance of different screening tests for the same disease
15
Q
What is lead-time bias?
A
- Due to early detection
- Screened group may appear to survive for longer after diagnosis because they are aware of their diagnosis earlier, when in fact life expectancy is unchanged.
16
Q
What is length-time bias?
A
- Cases detected through screening will tend to have less aggressive forms. This is because more aggressive forms will have shorter preclinical stage which screening can detect it in so less likely to be picked up this way
- This also means that survival will appear to be better in cases detected by screening than clinically
17
Q
What is selection bias in screening?
A
- Members of public who attend screening differ systematically from those who do not.
- Can work both ways e.g those at higher risk (FHx of breast cancer) may be more likely to attend, but also people with lower risk may attend (e.g high SES) - healthy screenee effect.
- Eliminated by RCT but may not be generalisable to real-world screening programme
18
Q
How can studies mitigate against lead and length time bias?
A
- Include all outcomes regardless of method of detection (symptoms and screening)
- Verify findings from observational studies with RCTs showing disease-specific mortality benefit for early detection and treatment
- Compare overall mortality from screened vs unscreened rather than survival time
19
Q
What ethical principle involves preventing harm in screening?
A
Non-malfeasance. Some harms include:
* Psychological harm from false positives
* Iatrogenic harm from subsequent diagnostic testing/treatment
* Unwarranted reassurance and even preventable death from false negatives
* Unecessary treatment in false positives
* Over-diagnosis in patients where disease would never have caused harm
20
Q
What ethical principle involves doing good in screening?
A
Beneficence
* Screening offers benefits to those who are true positives and detected early. However most people won’t benefit in this way
* E.g a concern is when screening primarily benefits society rather than the individual e.g TB screening for high-risk TB countries coming to UK
21
Q
What is autonomy in screening context?
A
- Should be provided with enough info about benefits and harms to make informed decision
- Questionable whether the majority of screening participants fully understand the consequences
22
Q
What is justice in a screening context?
A
- Need to ensure that screening doesn’t worsen health inequalities
- Often screening is an example of the prevention paradox
23
Q
What is the importance of consent in genetic screening?
A
Voluntary nature must be emphasized and education provided
24
Q
What is the role of counselling in genetic screening?
A
To provide information about genetic risk and reproductive options
25
What are the social implications of genetic screening?
Health beliefs and attitudes significantly influence participation
26
What is the primary concern regarding the use of genetic information by insurers?
Denial of access to health insurance or medical treatment
27
What is the target population for bowel cancer screening in the UK?
Men and women aged 50-74 and 74+ by request
28
What screening test replaced FOBT in 2017 for bowel cancer screening?
FIT (Fecal Immunochemical Test)
29
What is opportunistic screening?
Offering screening when a patient attends healthcare for another reason
30
What does the area under the curve (AUC) indicate?
AUC of 1 indicates a perfect test; 0.5 indicates a test equally likely to produce false positives or true positives
31
What is the purpose of genetic screening in the workplace?
Identify individuals at risk of occupational diseases
## Footnote
Employers may use genetic tests to discriminate against workers, but many already require medical exams.
32
What age group is targeted for bowel cancer screening?
Men and women aged 50-74 and 74+ by request
## Footnote
Screening occurs every 2 years with a national target of 60%.
33
What test replaced FOBT in bowel cancer screening?
FIT (Fecal Immunochemical Test)
## Footnote
FIT is more acceptable and easier to use.
34
What is the uptake percentage for bowel cancer screening?
66% uptake, with a 22% point gap in deprivation uptake
## Footnote
Females have higher uptake than males.
35
What is the national target for breast cancer screening?
70%
## Footnote
Screening occurs every 3 years for women aged 50-70.
36
What are the challenges faced in breast cancer screening?
Workforce issues, limited data output, previous non-attender letters
## Footnote
Incidence is rising but mortality reducing.
37
What is the uptake percentage for breast cancer screening in Scotland?
75.9%
## Footnote
A breast modernisation programme is in place from 2022-current.
38
What is the national target for cervical cancer screening?
80%
## Footnote
Screening occurs every 5 years for everyone with a cervix aged 25-64.
39
What is the uptake percentage for cervical cancer screening?
68.7%
## Footnote
Uptake is poorest in younger women and those with higher deprivation.
40
What new screening programs were recently expanded in pregnancy and newborn screening?
Screening for Edwards’ syndrome, Patau’s syndrome, and hereditary tyrosinaemia
## Footnote
Non-Invasive Prenatal Testing is also being evaluated.
41
What is the screening method for AAA in men aged 65?
One-off ultrasound
## Footnote
Aimed to reduce deaths by identifying aneurysms early.
42
What is the aim of diabetic eye screening?
Detect referable retinopathy to prevent sight-threatening conditions
## Footnote
Diabetic retinopathy is the leading cause of blindness among the working-age population in the UK.
43
What is the uptake percentage for diabetic eye screening?
Around 80%
## Footnote
The number of diabetics is increasing by around 4% per year.
44
Is prostate cancer screening recommended?
No, screening is not recommended
## Footnote
PSA test is not accurate enough and may lead to unnecessary treatments.
45
What is the role of the Scottish Screening Committee?
Oversight, assurance, and direction of screening programs
## Footnote
Includes operational delivery by NHS boards and program managers.
46
What inequalities exist in screening uptake?
Ethnic minority women, women with learning disabilities, and those with severe mental illness
## Footnote
Women in prison are also less likely to participate in cervical screening.
47
What is the evidence for lung cancer screening using low-dose CT?
Reduces lung cancer mortality and is acceptable to patients
## Footnote
Targeted for current or former smokers aged 55-74.
48
What should be included in informed consent for a screening test?
Details of test, possible side effects, likelihood of false positives/negatives
## Footnote
Also discuss the potential need for further tests.
49
What are the potential limitations of cervical cancer screening?
Regression can occur, and acceptability of the test may limit participation
## Footnote
Hr-HPV testing is more sensitive than cytology.
50
What is the Scottish Equity in screening access initiative?
A focus on addressing inequalities in screening access
## Footnote
Includes strategies like appointment reminders and self-testing options.
51
What are likelihood ratios and how are they interpreted?
* Estimates of how many times more likely individuals with the disease are to have a particular screening test result than those without the disease
* LR for a positive result indicates how much the odds of a disease increase when result is positive. true positive/false positive = sensitivity/(1-specificity)
* LR for negative result is how much the odds of disease decrease when test is negative. False negative/true negative = (1-sensitivity)/specificity
* Value <0.1: strong evidence against the diagnosis
* Value >10: strong evidence in favour of the diagnosis
52
What is pre- and post-test probability?
* Pre-test probability: probability, before the diagnostic test, that a patient has the disease. Can be based on prevalence or on estimation based on individual characteristics.
* Post-test probability: Estimated as PPV of a screening test, or more accurately for an individual from pre-test probability and LRs
* Pre-test odds = pre-test probability/(1-pre-test prob)
* Post-test odds = pre-test oddsxLR
* Post-test prob = post-test odds/(1-post-test odds)
