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Screening
Foundations of Biomedical Science 1
King's College London
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Define screening
Screening Actively identifying disease, or pre-disease, in apparently healthy subjects who may benefit from early treatment
Definition - A public health service in which members of a defined population, who do not necessarily perceive that they are at risk of, or are already affected by a disease or its complications are asked a question or offered a test to identify those individuals who are more likely to be helped than harmed by further tests or treatment to reduce the risk of disease or its complications
Outline the contribution of screening to disease prevention
Critically apply criteria that should be met for screening to be
worthwhile
Criteria The condition is important in terms of frequency, impact on affected individuals
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- Primary prevention is not effective or feasible
- There is an identifiable pre-clinical stage of disease There is a test that can separate those with a high probability of the disease from those with a low probability
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Effective treatment is available; the outcome of early treatment is better than later treatment after clinical diagnosis
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Describe national screening programmes in the UK
Screening
Friday, 15 March 2019 16:
- Inform women of results and refer them back to their GPs
Outline ethical issues raised by screening
Ethical Issues Those who are invited to participate are not patients Implementing informed consent Possible negative effects from participating in screening - Having a false positive result - Having a false negative - Being correctly identified as having the disease Dilemmas - Benefits must exceed harms - Resources used efficiently - Individual autonomy respected - Equity (fairness) promoted
Notes
Biases Lead Time Bias
Length-biased Rapidly progressive disease cause the individual to consult, but less rapidly progressing cases are likely to remain for screening detection Selection Bias Those entering screening are usually more conscious than those who decline Overdiagnosis Some lesions identified as disease in a screening programme would not have presented clinically during the individual's life time
Advantages and Disadvantages of Screening Advantages
g
- Improved prognosis for true positives
- Less radical treatment required
- May be resource savings
- Reassurance for those with true negative results Disadvantages
- Longer period of awareness for true positives whose prognosis is unaltered
- Over -treatment of borderline abnormalities
- False reassurance of false negatives
- Anxiety and hazard for false positives
- Hazard of screening test to all recipients
Screening
Module: Foundations of Biomedical Science 1
University: King's College London
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