Unit 2 - Levels of Evidence

Question 1

what is the definition of “level of evidence”?

Answer 1

• graded down on basis of study quality, imprecision, indirectness (study PICO doesn’t match questiosn PICO) because of inconsistency between studies, or because absolute effect is very small
• graded up if there is large or very large effect size

Question 2

which is better, a systematic review or an individual study?

Answer 2

systematic review

Question 3

how common is a step/level 1?

Answer 3

local and current random sample surveys/censuses

Question 4

how common is a step/level 2?

Answer 4

systematic review of surveys that allow matching to local circumstances

Question 5

how common is a step/level 3?

Answer 5

local non-random sample

Question 6

how common is a step/level 4?

Answer 6

case-series

Question 7

how accurate is the diagnostic/monitoring test for step/level 1?

Answer 7

systematic review of X-sectional studies with consistently applied reference standard and blinding

Question 8

how accurate is the diagnostic/monitoring test for step/level 2?

Answer 8

individual X-sectional studies with consistently applied reference standard and blinding

Question 9

how accurate is the diagnostic/monitoring test for step/level 3?

Answer 9

non-consecutive studies, or studies without consistently applied reference standards

Question 10

how accurate is the diagnostic/monitoring test for step/level 4?

Answer 10

case-control studies, or poor/non-independent reference standard

Question 11

how accurate is the diagnostic/monitoring test for step/level 5?

Answer 11

mechanism-based reasoning

Question 12

what will happen if we don’t add a therapy (prognosis) for step/level one?

Answer 12

systematic review of inception cohort studies

Question 13

what will happen if we don’t add a therapy (prognosis) for two?

Answer 13

inception cohort studies

Question 14

what will happen if we don’t add a therapy (prognosis) for 3?

Answer 14

cohort study or control arm of randomized trial

Question 15

what will happen if we don’t add a therapy (prognosis) for 4?

Answer 15

case-series or case-control studies, or poor quality prognostic cohort study

Question 16

does this intervention help (treatment benefits) in step/level 1?

Answer 16

systematic review`` of randomized trails of n-of-1 trials

Question 17

does this intervention help (treatment benefits) in step/level 2?

Answer 17

randomized trial or observational study with dramatic effect

Question 18

does this intervention help (treatment benefits) in step/level 3?

Answer 18

non-randomized controlled cohort/follow-up study

Question 19

does this intervention help (treatment benefits) in step/level 4?

Answer 19

case-series, or case-control studies, or historically controlled studies

Question 20

does this intervention help (treatment benefits) in step/level 5?

Answer 20

mechanism-based reasoning

Question 21

what are the common/rare (treatment) harms in terms of step/level 1?

Answer 21

systematic review of randomized trials, systematic review of nested case-control studies, n-of-1 trial witht he patient you are raising the question about, or observational study with dramatic effect
-if rare, only RCT or n-of-1 trials

Question 22

what are the common/rare (treatment) harms in terms of step/level 2?

Answer 22

individual randomized trial or (exceptionally) observational study with dramatic effect
-if rare, then not individual

Question 23

what are the common/rare (treatment) harms in terms of step/level 3?

Answer 23

non-randomized controlled cohort/follow up study (post-marketing surveillance) provided there are sufficient numbers to rule out a common harm (for long term, duration of follow-up must be sufficient)

Question 24

what are the common/rare (treatment) harms in terms of step/level 4?

Answer 24

case-series, case-control, or historically controlled studies

Question 25

what are the common/rare (treatment) harms in terms of step/level 5

Answer 25

mechanism-based reasoning

Question 26

is this screening test worthwhile in regards to step/level 1

Answer 26

systematic review of RCT

Question 27

is this screening test worthwhile in regards to step/level 2

Answer 27

randomized trial

Question 28

is this screening test worthwhile in regards to step/level 3?

Answer 28

non-randomized controlled cohort/follow up study

Question 29

is this screening test worthwhile in regards to step/level 4?

Answer 29

case-series, case-control, or historically controlled studies

Question 30

is this screening test worthwhile in regards to step/level 5?

Answer 30

mechanism-based learning