Screening Flashcards
What is screening ?
A process of identifying apparently healthy people who may be at increased risk of a disease or condition.
If a person is found to be at increased risk of a disease/condition, what are some steps which can be taken ?
Offered information, further tests and appropriate treatment to reduce associated risks or complications.
What are some of the main differences between screening and healthcare ?
Screening:
- mostly proactive
- targets asymptomatic patients
- implies benefit, but harms are always possible.
Healthcare:
- Patient initiated
- targets symptomatic patients
- possible hope or expectation but no promise of benefit
Give 3 examples of screening programmes for each of adults, pregnant women, and infants.
Adults:
Bowel cancer
Cervical cancer
Beast cancer
Pregnant women:
Fetal anomaly
Infectious diseases
Sick cell and thalassemia
Newborn and Infants:
Physical examination
Blood spot
Hearing
Describe the age, M/F, and frequency of screening for bowel cancel and breast cancer.
Bowel Cancer:
- M and F
- 50-74
- Every 2 years
Breast Cancer:
- F
- 50-70
- Every 3 years
What are the requirements for the screening of a condition to be viable and effective ?
- 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
What does sensitivity calculate in screening programmes ? What is for the formula for it ?
How well the test picks up having the disease
Sensitivity = (Number of results where disease detected in people with the disease / Number of people with the disease) x 100%
What does specificity calculate in screening programmes ? What is for the formula for it ?
How well the test detects not having the disease
Specificity = (Number of ‘normal’ results where disease is not detected in people without the disease /
Number of people without the disease) x 100%
What is the characteristic of a highly sensitive screening programme ?
Detects most of the disease
Very few false negatives
What is the characteristic of a highly specific screening programme ?
Correctly detects no disease
Very few false positives
What is a positive predictive value ?
“Probability that subjects with a positive screening test truly have the disease.”
What is a negative predictive value ?
“Probability that subjects with a negative screening test truly don’t have the disease.”
What is the formula for positive predictive value ?
(Number of people with the disease and a positive test result / Number of people with a positive test result) x 100%
What is the formula for negative predictive value ?
(Number of people without the disease and a negative test result / Number of people with a negative test result) x 100%
How are PPV and NPV affected by prevalence ?
“If we test in a high prevalence setting, it is more likely that persons who test positive truly have disease than if the test is performed in a population with low prevalence.”
What are the potential benefits of screening ?
- Reduced disease incidence (increased QOL)
- Reduced disease mortality
- Earlier, less radical treatment (increased QOL)
- Cost-effective
- Overall population benefit
- Reducing risks of developing serious condition or its complication
What are the potential harms of screening ?
- False reassurance
- Over-investigation and treatment
- Anxiety
- Longer period of morbidity with unaltered prognosis
- Harm from screening test
- Opportunity costs
- Increased health inequalities
What is the purpose of the Marmot Review of the UK Breast Screening Programme ?
Weights the benefits (e.g. deaths prevented) and harms (e.g. overdiagnoses ) of breast screening
What was the conclusion of the Marmot Review of the UK Breast Screening Programme ?
Significant benefits to the screening, so it should continue.
Communication about the benefits and harms with the women crucial.
What pieces of information which must be given to the patient before he/she can give informed consent to a screening procedure ?
- Purpose
- Potential risks and burdens
- Pathway following test results
What are some examples of biases in screening programmes ?
• Participant (volunteer) bias
– “When the subjects who volunteer to participate in a research project are different in some ways from the general population”
• Lead-time bias
– “An apparent increase in survival due to detecting a health condition such as cancer at an early stage, when there is no actual effect on survival, just a longer period with the diagnosis”
• Length-time bias
– Detection of less aggressive forms of condition in screening (“increases apparent survival”)
How can one measure the effectiveness of a screening ?
Randomised controlled trial
Time trend studies
Case control studies
Modelling studies
Compare breast, cervical, and bowel cancer in terms of incidence and mortality for different deprivation levels.
Bowel Cancer: Higher incidence and mortality for more deprived levels
Cervical cancer: More incidence and mortality for more deprived levels
Breast cancer: Slightly more incidence for less deprived levels, same mortality
Describe the potential impact of screening programmes on health inequalities ?
- Increased cost of treatment, social care etc
Why are the inequalities created by screening programmes illegal ?
Equitable outcomes are a legal requirement of Equality Act
With a = eligible population b = invited population
c = screened population, what is the formula for coverage ?
c/a x 100%
What are some challenges with optimising coverage ?
- Minority ethnic groups
- Immigrants
- Travellers
- Prisoners
- Students
- Reduced uptake
With a = eligible population b = invited population
c = screened population, what is the formula for uptake ?
c/b x 100%
What are some challenges with optimising uptake ?
- Change of address
- Communication
- Health literacy
- Deprivation
- Accessibility
- Vulnerable groups
What are some measures to improve screening engagement and uptake ?
- Promotion of screening programme
- Material in variety of languages
- “The wee C”
- “The Smear Amnesty”
- Toolkits for general practice
What are some inequalities which exist in uptake of screening, in addition to inequalities in wealth ?
Learning disability, sex, minority ethnicity and age.
What are some ways in which higher level of deprivation are affected by inequalities, regarding screening ?
Poorer outcomes, less lives saved, more treatment, reduced productivity (which threatens program viability)
As a result, less faith in the programme
What are some measures to improve engagement in vulnerable groups ?
• Social marketing
• Qualitative research
• Known effective interventions
– Letter from GP; patient navigation; community mentors; “people like me”; languages; text reminders;
• Known barriers
– Uncertainty of benefit; fear of cancer; lack of time; disgust/ discomfort/embarrassment;
