1 / 38

Prevention and Screening

Prevention and Screening. MMS Year 4 Public Health Workshop in O&G. Why is prevention better than cure?. Hygieia – goddess of health. McKeowan (1979) and Illich (1976). Personal medical care has contributed relatively little to the improvements in mortality since 1800s. Medical care.

mfurness
Download Presentation

Prevention and Screening

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Prevention and Screening MMS Year 4 Public Health Workshop in O&G

  2. Why is prevention better than cure? Hygieia – goddess of health

  3. McKeowan (1979) and Illich (1976) • Personal medical care has contributed relatively little to the improvements in mortality since 1800s

  4. Medical care • Bunker 1995 • Only 2 years of the 23 years increase in longevity is due to medical intervention between 1900-1950 • But since 1950, 3 out of the 7 years increased life expectancy • Why?

  5. Prevention • Primary prevention • Stopping a disease from occurring (incidence) • Secondary prevention • Detecting a disease early to allow early intervention to reduce mortality and morbidity • Tertiary Prevention • Stopping the recurrence or complications of a disease

  6. Why do we do them? • Intuitive • Cost • Benefit • Quality of life • Morbidity • Mortality • So why don’t we do them for everything?

  7. Why don’t we do them • Cost • Benefit • Evidence based • Early detection • Treatment • Ethical (Abdominal Aortic Aneurysm) • Intuitive • Persuasion • Side effects (pertussis) • Harm (MMR, psychological) • Risk no longer exists

  8. TASK: Why do you wear a seatbelt?

  9. Prevention Paradox • Rose 1981 • “A preventative measure that brings large benefits to the community offers little to each participating individual.”

  10. Secondary/Tertiary Prevention

  11. Screening: doing more good than harm Mission of the National Screening Committee

  12. What is screening? • ‘Healthy’ population • Asked a question or offered a test • Identifies individuals who are more likely to be helped than harmed by further tests or treatment to reduce the risk of a disease or its complications

  13. Limitations of Screening • Ethical differences from clinical practice for people who present with symptoms • Should help individuals to make informed choices about their health • Risks as well as benefits

  14. TASK: What screening programmes are NHS funded? • Rapid list on the whiteboard

  15. Animation http://cpd.screening.nhs.uk/timeline

  16. Criteria for Screening Programmes Ideally all criteria should be met!

  17. The Condition • Important health problem • Natural history understood • development from latent to declared disease • detectable risk factor • disease marker • Cost-effective primary prevention interventions implemented • Carriers identified as a result of screening • natural history of this status understood • psychological implications

  18. The Test • Validated screening test • Simple • Safe • Precise • Test values in the target population known • suitable cut-off level defined and agreed • Acceptable to the population • Agreed investigation if positive test • With choices • For mutations • the criteria for subset of mutations to be covered

  19. The Treatment • Effective treatment or intervention • evidence of early treatment leading to better outcomes • Evidence based policies covering • individuals should be offered treatment • appropriate treatment to be offered • Clinical management and patient outcomes should be optimised

  20. The Screening Programme • Randomised Controlled Trials • effective in reducing mortality or morbidity • evidence from trials for informed decision making that the test accurately measures risk • Acceptable to professionals and the public • Clinically • Socially • Ethically • Benefit outweigh the physical and psychological harm • Opportunity cost • value for money

  21. The Screening Programme • Plan for managing and monitoring programme • quality assurance standards • Adequate staffing and facilities • All other options considered • more cost effective intervention? • Evidence-based info allowing informed choice • consequences of testing • investigation and treatment • Anticipate public pressure • widening the eligibility criteria • reducing the screening interval

  22. Sensitivity • The proportion of truly diseased patients in the screened population who are identified as diseased by the screening test. • The probability of correctly diagnosing a case • True positive rate

  23. Specificity • The proportion of truly non-diseased persons who are so identified by the screening test. • The probability of correctly identifying a non-diseased person with a screening test • True negative rate • This is what a clinician or the patient wants to know

  24. Example 1

  25. Sensitivity 20/100 0.2 20% Specificity 890/900 0.99 99% Answer

  26. Example 2

  27. Answer • Sensitivity • 80/100 • 0.2 • 80% • Specificity • 895/900 • 0.99 • 99%

  28. Positive Predictive Value • The probability that a person with a positive test is a true positive • Does have the disease • This is what a clinician or the patient wants to know

  29. Negative Predictive Value • The probability that a person with a negative test is a true negative • Does not have the disease

  30. Positive Predictive Value = a/ (a+b) Negative Predictive Value = d/(c+d)

  31. Example 3

  32. PPV 20/30 0.67 67% NPV 890/970 0.92 92% Answer

  33. Example 4

  34. Answer • PPV • 80/85 • 0.94 • 94% • NPV • 895/915 • 0.97 • 97%

More Related