Screening Flashcards
What is screening?
• Screening is the process of identifying healthy people who may have an increased chance of a disease or condition.
• The screening provider then offers information, further tests and treatment. This is to reduce associated problems or complications.
(UK National Screening Committee 2018)
(Screening)… encompasses the whole system or programme of events necessary to achieve risk reduction. Screening is a programme, not a test.
(Raffle and Muir, 2009)
Why do screening?
Screening can:
• save lives or improve quality of life through early identification of a condition
• reduce the chance of developing a serious condition or its complications
What are the Wilson and Jungner criteria on the condition screened for for proposed screening?
The Condition
• Important public health problem
• Natural history understood
• Recognizable latent or early symptomatic phase
What are the Wilson and Jungner criteria on the test used for proposed screening?
The Test
• Simple, safe, precise and validated
• Acceptable
• Distribution of test results known and cut-off defined
• Agreed policy on further diagnostic investigations
What are the Wilson and Jungner criteria on the treatment used for proposed screening?
• Effective and available
What are the Wilson and Jungner criteria on the screening program proposed for a condition?
- Evidence from RCTs that screening is effective/accurate
- Clinically, socially and ethically acceptable
- Cost effective
- Quality assured
What is the WHO screening criteria 2008?
• 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
“primum non nocere”
What are the current UK screening programs for adults?
Abdominal aortic aneurysm - M 65 one off
Bowel cancer - M+F 50-70 every 3 years
Breast cancer - F 50-70 every 3 years
Cervical cancer - F 25 - 64 every 3 years
Diabetic retinopathy - M+F Diabetics >=12 annually
What are the current UK screening programs during pregnancy?
Fetal anomaly
Infectious diseases
Sickle cell and thalassemia
What are the current UK screening programs for newborns and infant?
Physical examination
Blood spot
Hearing
How do you asses how good a screening test is?
• How does it perform?
– What is its sensitivity?
– What is its specificity?
• When applied to your population, how accurate are the results achieved?
– Positive predictive value
– Negative predictive value
What is sensitivity in regards to screening?
how well the test picks up having the disease
Number of results where disease detected in people with the disease
______________________________
Number of people with the disease
What does a highly sensitive test do?
– Picks up most of the disease
– Very few false negatives
What does a highly specific test do?
– Correctly detects no disease
– Very few false positives
What is positive predictive value?
how reliable is the test result which shows disease is present?
Number of people with the disease and a positive test result ______________________________
Number of people with a positive test result (ie showing disease)