Unit 2 - Levels of Evidence Flashcards
what is the definition of “level of evidence”?
- 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
which is better, a systematic review or an individual study?
systematic review
how common is a step/level 1?
local and current random sample surveys/censuses
how common is a step/level 2?
systematic review of surveys that allow matching to local circumstances
how common is a step/level 3?
local non-random sample
how common is a step/level 4?
case-series
how accurate is the diagnostic/monitoring test for step/level 1?
systematic review of X-sectional studies with consistently applied reference standard and blinding
how accurate is the diagnostic/monitoring test for step/level 2?
individual X-sectional studies with consistently applied reference standard and blinding
how accurate is the diagnostic/monitoring test for step/level 3?
non-consecutive studies, or studies without consistently applied reference standards
how accurate is the diagnostic/monitoring test for step/level 4?
case-control studies, or poor/non-independent reference standard
how accurate is the diagnostic/monitoring test for step/level 5?
mechanism-based reasoning
what will happen if we don’t add a therapy (prognosis) for step/level one?
systematic review of inception cohort studies
what will happen if we don’t add a therapy (prognosis) for two?
inception cohort studies
what will happen if we don’t add a therapy (prognosis) for 3?
cohort study or control arm of randomized trial
what will happen if we don’t add a therapy (prognosis) for 4?
case-series or case-control studies, or poor quality prognostic cohort study
does this intervention help (treatment benefits) in step/level 1?
systematic review`` of randomized trails of n-of-1 trials
does this intervention help (treatment benefits) in step/level 2?
randomized trial or observational study with dramatic effect
does this intervention help (treatment benefits) in step/level 3?
non-randomized controlled cohort/follow-up study
does this intervention help (treatment benefits) in step/level 4?
case-series, or case-control studies, or historically controlled studies
does this intervention help (treatment benefits) in step/level 5?
mechanism-based reasoning
what are the common/rare (treatment) harms in terms of step/level 1?
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
what are the common/rare (treatment) harms in terms of step/level 2?
individual randomized trial or (exceptionally) observational study with dramatic effect
-if rare, then not individual
what are the common/rare (treatment) harms in terms of step/level 3?
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)
what are the common/rare (treatment) harms in terms of step/level 4?
case-series, case-control, or historically controlled studies
