PHEPB: Screening and secondary prevention Flashcards
What are the types of prevention?
What is the aim of secondary prevention?
Aim of screening is to get early cases of disease, to prevent conversion into disease - this helps pts have a better prognosis, and is more cost effective for the health system
Screening is purely for those that are asymptomatic
Consequences of screening?
With screening more cases would be detected “early”
but at the cost of individuals without disease having to undergo further diagnostic procedures due to false positives
The health service has to have facility to cope with the increase demand of managing all “screen positives”
Some people may detect cancer, and may have actually never developed the disease in their lifetime - but they still will undergo further investigations due to screening
Some people will suffer by simply knowing they have cancer when they otherwise would have been physically okay
Screening tests are usually compared with a…
Screening tests are usually compared w a gold standard (reference standard); current best diagnostic test/ diagnostic case definition
Fixed test characteristics lead to PPV, OA, PR, NPV
Usually when we bring in a new test, we try to compare it against some kind of reference standard that is used, in terms of diagnosing a particular condition
Screening can also be for pregnancy/congenital abnormality
Describe an example of screening for ovarian cancer.
How would you find the detection rate of a screening test? Use this data
Detection → “how good is the test at detecting the disease?”
Use this data to work out the false positive rate of screening test.
What is the difference between specificity and false positive rate? Overall how good of a screening test is this?
Detection rate (sensitivity) = 50%
False positive rate = 7%
(Specificity 93%)
This is probably not a good screening test - picks up only have cases of cancer- could be good if it is cheap, but also is affecting those who do not have the disease
What is the PPV? Use this data to work it out
What is the OAPR? Use this data to work it out
So what is the difference between OAPR and PPV?
What is NPV?
How good is the new Covid Ab test? Use this info to find the detection rate, Specificity and FPR
What is the requirement for a worthwhile screening programme?
Disorder is well defined medically
Disorder has high prevalence and is of public health importance
Natural History: possible to identify early disease from healthy
Treatment: no point screening if no treatment exists
Test should be simple, safe, accessible to all, and accurate.
Ethical: The test & procedures after a positive result should be acceptable to both screener & individual
Adequate health provision for the extra clinical workload
resulting from the screening
What are the financial requirements for a worthwhile screening programme?
Financial: Cost-effective
Early detection & treatment vs. late diagnosis & treatment
Costs should be balanced against:-
(i) risks - hazards associated diagnostic test, interventions / treatment
(ii) benefits - reduction in morbidity or mortality
