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Flashcards in Other bits Deck (14)
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1

Define screening

presumptive identification of unrecognised disease
using a test or procedure which can be applied rapidy
to sort out apparently well persons who propbably have a disease from those who probably do not

2

What are the principles of a good screening programme when it comes to the disease

known aetiology and risk factors
known natural history
high incidence/.prevalence
high morbidity/mortality

3

What are the principles of a good screening programme when it comes to the test

simple
acceptable
valid
reliable

4

What are the principles of a good screening programme when it comes to the treatment

available
effective
acceptable
benefits from early detrtection

5

What are the principles of a good screening programme when it comes to the programme

cost-effective
agreed protocol
quality assurance
does more good than harm

6

Define sensetivity

people with the disease having an abnormal result
/ all people with disease

7

Define specificity

people without disease having normal test result
/ all people without disease

8

define positive predicitve value

people with disease who had abnormal test result
/ all people who tested positive

how likely an abnormal test result is going to be right

9

define negative predictive value

people without disease with normal test result
/ all people with normal test result

10

What affects the PPV and NPV

the specificity and sensitivity
the prevalence - high prevalence = high PPV and low NPV

11

What are the consequences of a high PPV

many people would have an abnormal test result
anxiety and stress
unnecessary investigations
to then find out they are fine!

12

What are the consequences of a low NPV

many people with abnormal result assume they are fine
delay seeking medical advice
when they might have the disease!

13

What is lead-time bias

screening brings forward time of diagnosis, so it looks as if survival time has increased.
infact, the time of diagnosis has just been changed, still die at same time!

14

What is length bias

selective detection of less aggressive cancers by a screening programme which would have better prognosis anyway
aggressive cancers grow more rapidly, so there is less of a chance for a screening test o detect them
survival results are better for those detected by screening, but this would have been the case anyway due to the cancer being less aggressive!