screening - course guide

Question 1

when is screening carried out

Answer 1

early detection = better prognosis
identify people at risk where interventions will reduce the risk
infectious disease - treatment improve outcome/prevent transmission

Question 2

limitations

Answer 2

may do more harm than good - raise anxiety and overtreatment

Question 3

describe screening tests

Answer 3

simple, safe, acceptable, cheap, repeatable and valid

Question 4

what does valid mean

Answer 4

sensitive and specific

ability to distinguish between thos woth and those w/o

Question 5

how can you assess validity

Answer 5

with a definitive diagnostic test - gold standard

measure specificity, sensitivity, predictive value

Question 6

sensitivity

Answer 6

the ability of the test to correctly identify people with the disease

Question 7

specificity

Answer 7

the ability of the test to correctly identify people without the disease

Question 8

positive predictive value

Answer 8

the likelihood that a patient with a positive test result will actually have the disease

Question 9

-ve predictive value

Answer 9

the likelihood that a patient with a negative test result will not have the disease

Question 10

who is screening targeted at

Answer 10

the mass, or targeted groups
systematic program
or opportunisitic

Question 11

what is tested for in antenatal screening

Answer 11

syphilis
HIV
hepatitis B
rubella
chromosome abnormalities
foetal growth

Question 12

screening in neonates and childhood

Answer 12

phenylketonuria
hypothyroidism
haemoglobinopathies
sickle cell disease 
congenital hip dislocation 
hearing and development

Question 13

cancers screened for

Answer 13

breast
cervical
bowel 60-69

Question 14

infections screened for

Answer 14

chlamydia
Hep B - health workers
HIV

Question 15

CVD screened for

Answer 15

abnormal aortic aneurysm 
diabetic retinopathy - 12<
Bp
high cholesterol
diabetes

Question 16

criteria

Answer 16

important health problem
recognised and identifiable at pre-clinical stage
natural history of disease understood
long time between 1st signs and overt disease
valid
simple and cheap
safe and acceptable
reliable facilities are adequate
effective, acceptable and safe treatment available
cost effective
sustainable

Question 17

3 issues that evaluate screening tests

Answer 17

feasibility
effectiveness
cost

Question 18

cost

Answer 18

relative cost-effectiveness compared to other forms of healthcare
look at cost of diagnositic tests and treatment compared to treatment in later stages

Question 19

feasibility

Answer 19

easy to organise population for screening
test acceptable
facilities and resources for tests after screening

Question 20

effectiveness

Answer 20

extent that it affects outcomes
selection bias - people who participate differ from people who don’t
lead time bias - apparent longer survival but really just because diagnosed earlier
length bias - some things have longer preclinical stage, have a more favourable prognosis - screening doesn’t increase life

Question 21

ethics

Answer 21

can do harm 
risk from the test/diagnostic test 
false +ve = anxiety 
unplanned effects of +ve test 
false -ve give false reassurance

Question 22

prognosis

Answer 22

the outcome of an illness, including duration of disease, mortality and morbidity.

Question 23

gold standard

Answer 23

a recognised way of determining who really has the disease

Question 24

Receiver Operator Characteristics (ROC) curves

Answer 24

used to determine a cut off value for a diagnostic/screening test
y axis 1- sensitivity, x axis 1 - specificity
choice of a particular cutoff value for a test is informed by the attempt to maximize sensitivity and specificity.

Question 25

prevalence

Answer 25

the proportion of people in a population with a disease