evidence based medicine

Question 1

best study to determine prevalence of a disease

Answer 1

cross sectional study

Question 2

a study that compares 2 groups of 4 y/o with similar characteristics: one group is given a drug + the other a placebo, growth of each is measured after this intervention - what kind of study?

Answer 2

controlled trial

Question 3

a study that aims to establish the noraml height of 4y/o by measuring heights at school entry

Answer 3

cross sectional

Question 4

screening

Answer 4

a process of idenitifying apparently healthy people who may be at increased risk of disease or condition

(normal/negative result on screening does not equal disease free necessarily)

Question 5

sensitivity

Answer 5

how well the test detects having the disease

no of results where test is positive in those with disease / numbr of people with the disease

Question 6

specificity

Answer 6

how well test detects NOT having the disease

no of “normal” results where disease in NOT detected in people WITHOUT the disease / no of people without disease

Question 7

positive predictive value

Answer 7

how reliable is the test result when it shows disease is present

no of people with a positive test + have disease / number of people with a pos test

Question 8

neg predicitve value

Answer 8

how reliable is the test result when disease NOT present

no of people who have a neg test result + do NOT have disease / no of people with a neg test result

Question 9

effect of prevalence on positive + negative predictive values

Answer 9

As prevalence increases -> PPV also increases but the NPV decreases

prevalence decreases -> PPV decreases while the NPV increases

Question 10

a study that compares the height of a group of 4y/o living near a nuclear plant with the height of a group of 4y/o who live elsewhere

Answer 10

case control studies

Question 11

controlled trial vs case control studies

Answer 11

controlled - one group given drug the other placebo + compares (you’re adding something)

case control - comparing outcomes of people in different locations (environment all ready exists)

Question 12

kids born at one hospital 1 year + measure their height at intervals of up to 4yrs of age

Answer 12

cohort study

Question 13

external validity

Answer 13

the extent to whoch one can appropriately apply the results to other popultions

OTHER -> external validiation

Question 14

which study design is the best to research the aetiology of a disease?

Answer 14

cohort

-> time frame important

Question 15

define statistical significance

Answer 15

the results of a study are unlikely to have arisen by chance alone

Question 16

what does qualitative research seek to analyse?

Answer 16

the date which reserachers collect from people in relation to their experiences + circumstances

Question 17

saturation

Answer 17

no longer any need to sample more people to reach new conclusion or to back up or challenge existing conclusions

Question 18

absolute risk (AR)

Answer 18

the number of events in treated or control groups, divided by the number of people in that group

ARC = AR of events in the control group
ART = AR of events in the treatment group

ARR(absolute risk reduction) = ARC - ART
RR ( relative risk) = ART / ARC

Question 19

how is the number needed to treat calculated?

Answer 19

NNT = 1/ARR –> (1 in …)

ARR (absolute risk reduction) = ARC - ART