(6) Screening Flashcards
List at least six criteria to approve a screening system.
- Quick & cheap & acceptable to populations
- Serious health conditions
- Well known epidemiology and natural history
- Defined cut-off points of positives and negatives
- Defined people who to be screened for
- Already available effective preventive treatments
- Invasiveness of screening benefits > harms
- Early detection available
What are: True positives, False positives, True negatives and False negatives?
- True positives = detected diseased people
- False positives = detected UN-diseased people
- True negatives = excluded un-diseased people
- False negatives = excluded DISEASED people
What are Specificity and Sensitivity? How are they calculated?
- Sensitivity = proportion of DISEASED people who are tested positive; (True positives) / (True positives & False negatives)
- Specificity = proportion of UN-diseased who are tested negative; (True negatives) / (True negatives & False positives)
What are the value of the following indicate?
- (True positives) / (True positives & False negatives)
- (True negatives) / (True negatives & False positives)
- Sensitivity
- Specificity
What are True Predicted Value and False Predicted Value? How are they calculated?
- PPV = proportion of people who are tested positive are actually DISEASE; (True positives) / (True & False positives)
- NPV = proportion of people who are tested negative are actually UN-diseased; (True -ve) / (True & False -ve)
What are the value of the following indicate?
- True positives) / (True & False positives)
- (True negatives) / (True & False negatives)
- True Predicted Value
- False Predicted Value
Explain what is Lead Time Bias?
Patients actually have same life expectancy, but those screened detected earlier so seemed lived longer
Explain what is Length Time Bias?
Screening is better at picking up non-threatening diseases, so life expectancy seemed longer if detected
Explain what is Selection Bias?
Those chose to be screened are more likely to engage healthy behaviours.
Define screening
- Systemic attempts
- Detect unrecognised conditions
- Those at high risks
- Cheaply & rapidly
Suggest ways we might detect disease (3).
- Spontaneous presentations from patients seeing GPs
- Opportunistic detections when looking for something else
- Screening
List the criteria for implementing a screening programme relating to the DISEASE (4).
- Serious (QoL or death)
- Well understood natural history & epidemiology
- Dearly detectable stage
- Cost-effective primary prevention available
List the criteria for implementing a screening programme relating to the TEST (4).
- Quick
- Precise & valid
- Acceptable
- Defined cut-off positives/negatives
List the criteria for implementing a screening programme relating to the TREATMENT (2)
- Early treatment must be advantageous
- Effectiveness
List the criteria for implementing a screening programme relating to the PROGRAMME (4)
- Effective (RCT)
- Benefits > psychological harm
- Facilities for diagnosis & treatments
- Facilities for consolling
What two types of error in the results do screening programmes make? What are some of the issues for the people with these errors?
- False positives: give stress, anxiety, unnecessary treatment, cost to diagnose them)
- False negatives: inappropriate reassurance leading to late presenting to be diagnosed
How do you calculate the prevalence of a disease?
(True positives + False negatives) / (All values)
Why can screening provide an issue for the doctor performing it? Compared to normal patient presentation)
If the patient presents with an issue and it is bad news then it’s a sad time, but the doctor has no involvement but helping them. However id and issue is picked up in screening then a doctor has actively gone out to tell you this.
Suggest some sociological critiques of health promotion and screening (4).
- Structural: victims blame it become their responsibilities to check & why not do primary prevention to exposures
- Surveillance: is it a social control?
- Social construction: given meaning through particular social relationships, you should go to screening as it’s the right thing to do
- Female are more targeted to be screened?
Give examples of screening programmes in the UK (9)
- Abdominal Aorta Aneurysm
- Breast Cancer
- Cervical Cancer
- Bowel Cancer
- Diabetic Retinopathy
- Down’s Syndrome
- Foetal Abnormalities
- Parkinson’s Disease
- Sickle Cell & Thalassaemia
What type of bias is: Patients actually have same life expectancy, but those screened detected earlier so seemed lived longer
Lead time bias
What type of bias is: Screening is better at picking up non-threatening diseases, so life expectancy seemed longer if detected
Length time bias
What type of bias is: Those chose to be screened are more likely to engage healthy behaviours.
Selection bias
