screening Flashcards
is it normal to be screened in the uk
no it is rare
what is screening
a process which sorts out apparently well people who probably have a disease (or precursors or susceptibility to a disease) from those who probably do not
is screening intended to be diagnostic
no
types of prevention
primary prevention
secondary prevention
tertiary prevention
main purpose of screening
secondary prevention
detect early disease to alter the course of the disease
what does screening want to achieve
- reduce the risk of developing disease
- provide treatment
- provide information
define sensitivity
the proportion of people with the disease who are correctly identified by the screening test
define specificity
the proportion of people without the disease who are correctly excluded by the screening test
define positive predictive value
the proportion of people with a positive test result who actually have the disease
define negative predictive value
the proportion of people with a negative test result who do not have the disease
what are predictive values dependent on
underlying prevalence
whereas sensitivity and specificity are not
what is screening criteria based on
wilson and jugner criteria
what is the wilson and jugner criteria for the condition
- the condition should be an important health problem
- the natural history of the condition should be well understood
- there should be a detectable early stage
what is the wilson and jugner criteria for the treatment
- there should be an accepted treatment for patients with recognised disease
- facilities for diagnosis and treatment should be available
- adequate health service provision should be made for the extra clinical workloud resulting from screening
what is the wilson and jugner criteria for the test
- a suitable test should be devised for the early stage
- the test should be acceptable
- intervals for repeating the test should be determined (not a one off)
what is the wilson and jjugner criteria for the risks and benefits
- there should be an agreed policy on whom to treat
- the costs should be balanced against the benefits
- the risks, both physical and psychological, should be less than the benefits
3 types of biases
selection bias
lead-time bias
length-time bias
what is selection bias
people who choose to participate in screening programmes may be different from those who do not
describe breast cancer screening
eligible group - women
test - 2 view mammography
further tests - mammography, biopsy, ultrasound, cytology
treatment - surgery, radiotherapy, chemotherapy
avoiding - overall deaths in screened women
5 types of screening
- population based screening programmes
- opportunistic screening
- screening for communicable diseases
- pre employment and occupational medicals
- commercially provided screening
