L04: Secondary Prevention Flashcards
What is the definition of screening
Identifying apparently healthy people who may be at risk of a disease
Why is screening beneficial
It leads to early detection of disease and early treatment to reduce complication
What are the ways we can screen
Questionaire
Examination
Lab test
Imaging
After screening what are the 4 groups of results people are defined into
True negative
True positive
False negative
False positive
What is a true negative
Someone who does not have the disease and shows as negative in the test
What is a false negative
Someone who does have the disease but shows as negative on the test
What is a true positive
Someone who has the disease and tests as positive on the test
What is a false positive
Someone who doesn’t have the disease but shows as positive on the test
What does sensitivity mean
The rate of true positive
What is the equation for sensitivity
(True positive)/ all positive i.e false positive and false negative
What is a specificity
The rate of true negative
What is the equation for specificity
True negative/(true negative+ false positive)
When is the sensitivity more useful to use
When the result is negative
When is a specific test more useful
When the result is positive
What is a predictive value look at
The likely hood of you testing positive and having the disease to the likelihood you testing negative and not having the disease
What do predictive values depend on
Prevalence of the disease
Is a screening test and a screening programme the same thing
No
What is a screening programme
A systematic process that sends the invitation to apparently healthy individuals they further investigate,assess and diagnose those who are positive.
What are the 3 biases that can occur in screening
Volunteer bias
Lead time bias
Length bias
What is a volunteer bias
People who attend to screening have a low risk of the disease compared to those who do not attend
What is a lead time bias
The time by which diagnosis is advanced because of screening so it is an apparent increase in survival
What can lead time bias result in
The same survival rate but the patient who got diagnose before is aware of the illness for more years
What is length time bias
Those with a slow progressive disease are more likely to be detected by screening than those who have a rapidly progressive disease
What are the factors that influence screening policy
Evidence
Values
Commercial interest
What are the criteria’s for assessing the appropriateness of implementing a screen programme
1) the condition: history has to be understood and primary prevention has to be implemented
2) the test: has to be suitable and valid
3) the intervention: has to have an effective treatment and policy on who we treat
4) screening programme: clinically, socially and ethically acceptable, the benefits outweigh the harms
5) implementation of programme: clinical management and patient outcomes should be optimised
