B8-045, B8-073 EBM Lectures

Question 1

screening tests should have high […]

Answer 1

sensitivity

Question 2

diagnostic tests should have high […]

Answer 2

specificity

Question 3

[…] test identifies a patient at risk for the condition

Answer 3

screening

Question 4

[…] test determines presence of condition

Answer 4

diagnostic

Question 5

calculation for senstivitiy

Answer 5

true positives/ disease positives

or TP/(FN + TP)

Question 6

calculation for specificity

Answer 6

true negative/disease negatives

or TN/(FP+TN)

Question 7

calculation for false positive rate

Answer 7

FP/(FP+TN)

or 1-specificity

Question 8

calculation for PPV

Answer 8

TP/Test +

or (TP/TP+FP)

Question 9

used to define a “cut off” value for a test

Answer 9

ROC curves

Question 10

in ROC curves, the area under the curve can be used to compare

Answer 10

different tests

Question 11

pretest probability and likelihood ratios can be used to determine

Answer 11

post-test likelihood of disease

Question 12

calculation for LR positive

Answer 12

sensitivity/ (1-specificity)

Question 13

calculation for LR negative

Answer 13

(1-sensitivity)/ specificity

Question 14

if LR = 0, the test has […] value

Answer 14

no discriminatory

Question 15

if LR+ is greater than or equal to 10, the test has […] value

Answer 15

high diagnostic value

Question 16

if LR- is less than or equal to 0.1, the test has […] value

Answer 16

high diagnostic value

Question 17

cross sectional studies are good at identifying [incidence/prevalence]

Answer 17

prevalence

Question 18

what type of study design can be used to estimate exposure/disease burden?

Answer 18

cross-sectional

Question 19

what type of study design can quickly be used to study several exposures/disease simultaneously?

Answer 19

cross-sectional

Question 20

what type of study design can be used to compare rate of diseases between populations?

Answer 20

ecologic study

Question 21

what type of study design is efficient for rare exposures?

Answer 21

observational cohort

Question 22

what type of study design establishes temporal relationship between exposure and outcome?

Answer 22

observational cohort

Question 23

what type of study design can be used to compare aggregate data across groups?

Answer 23

ecologic studies

Question 24

relationships observed for groups are assumed to hold true for individuals

Answer 24

ecological fallacy

Question 25

subjects alter behavior when they know they are being studied

Answer 25

Hawthorne effect

Question 26

[...] bias: investigator's evaluation is impacted by knowledge of exposure status

Answer 26

observer bias

Question 27

[...] bias: exposure and control group are not treated equally

Answer 27

procedure bias

Question 28

[...] bias: subjects provide inaccurate data

Answer 28

information bias

Question 29

[...] bias: study population not representative of intended source poplulation

Answer 29

selection bias

Question 30

the key indicator in evaluating effectiveness of a screening tool is

Answer 30

reduction in mortality

Question 31

in areas of higher prevalence, PPV is [...] and NPV is [...]

Answer 31

in areas of higher prevalence, PPV is [higher] and NPV is [lower]

Question 32

higher prevalence increases

Answer 32

pretest probability

Question 33

a variable other than the one being studied influences the results

Answer 33

confounding error

Question 34

a type of bias in which the patients in a study are not randomly assigned to a treatment group

Answer 34

selection bias

Question 35

selection bias can be avoided by

Answer 35

randomization

Question 36

[...] bias occurs when information is gathered at an inappropriate time in the study

Answer 36

late-look bias (ex. sample of patients has less severe disease because those with more severe disease have died)

Question 37

[...] bias occurs when the temporal characteristics of a disease are not considered

Answer 37

lead time bias (important to consider in screening tests, can inflate survival time due to early detection)

Question 38

[...] bias occurs when patients reports of the past are selective or exaggerated

Answer 38

recall (common in case control studies)

Question 39

how can recall bias be reduced?

Answer 39

decreasing time from exposure to follow up

Question 40

[...] bias occurs when data outcomes are distorted by how data are gathered

Answer 40

measurement (ex. Hawthorne effect)

Question 41

how can measurement bias be reduced?

Answer 41

placebo groups using objective and proven methods of data collection

Question 42

the proportion of people who have a condition at one point in time

Answer 42

prevalence

Question 43

how is prevalence calculated?

Answer 43

number of individuals with illness/total population

Question 44

[...] disease prevention is preventing the actual occurrence of disease

Answer 44

primary (ex. providing free condoms, vaccinations)

Question 45

[...] disease prevention is aimed at early detection

Answer 45

secondary (ex. screening tests, regular BP measurements)

Question 46

[...] can help ensure appropriate external validity

Answer 46

randomization