Course Basics Flashcards
What are the percentages for Side Effects descriptions according to EU?
Very common means >10%
Common means 1-10%
Uncommon means 0.1-1%
Rare means 0.01-0.1%
Very rare means <0.01%
What are the percentages for Side Effects descriptions according to patients?
Very common means 65%
Common means 45%
Uncommon means 18%
Rare means 8%
Very rare means 2%
What’s the perception of high risk to patients?
Most think it’s between 41-50% risk (not true).
Top 5 trial design features of prospective controlled trials
- Randomized
- Double blind
- Allocation concealment
- > 80% of patients at study completion
- Valid clinic outcomes selected (important for patients and clinician)
Why is important to randomize trials?
- Because to assess the effectiveness of a treatment requires a comparison. By doing it random, it gives a more equivalent comparison between groups.
- in non-randomized comparisons, other factors may explain any differences observed (confounding)
- randomization controls for both known and unknown confounders
What is evidence-based practice?
The integration of best research evidence with clinical expertise and patient values.
Barriers to evidence-based practice
- Limited awareness/knowledge
- Limited time
- Limited amount of well designed trials in your practice area
- Lack of motivation (lack of skills/financial incentives)
- Inadequate literature searching skills
- Abundance of information
Clinical Questions (PICO)
Patient: what’s the population age, gender, condition hx..description of the most important characteristics of the patient or target disorder.
Intervention: What do you want to do for the patient? could include exposure, diagnostic test, prognostic factor, surgery, therapy or patient’s perception.
Comparator(s): Relevant alternative(s) most often considered for this type of patient. Could be the gold standards or anything else.
Outcome: clinical outcome of interest to you and your patient. Like increasing mortality (live longer) and quality of life. Goes beyond lab values.
What is the importance of good clinical questions?
- With limited amount of time, is important to ask questions that by design focus on evidence that is directly relevant to the patient’s clinical needs and our knowledge needs.
- Good questions can suggest high yield search strategies.
- Questions suggest forms that useful answers might take.
What is the best evidence for a Therapeutic Intervention?
RCT or systemic review/meta-analysis
What is the best evidence for a Rare Side Effect?
Case control study
What is the best evidence for an Exposure to a potential toxin?
Cohort study
What is the best evidence for an evaluation of a new drug by Medicare?
Pharmacoeconomic analysis
Trial Designs for Therapy Questions
- Randomized controlled trials (RCTs)
- Systemic review (SR)
- Studies
- Meta-analysis (MA)
What is a systemic review?
Process to identify, synthesize, and evaluate the available literature.
What studies are good to answer therapy questions?
Those:
1. identified according to an explicit search strategy
2. selected by defined inclusion & exclusion criteria
3. evaluated against consistent methodological standards
What are meta-analysis?
A statistical process for quantitatively estimating the net benefit/risk from the results of the included studies.
Where to find the best evidence?
- textbooks
- journals
- phone a friend
- medine
- the cochrane library
- evidence based journals (ACP journal Club, EBM)
- internet websites (drug information websites, evidence-based practice websites, therapeutic specialty websites, healthcare websites)
Hierarchy of Evidence for Therapy Studies
(From top of triangle to bottom)
Meta-analysis of RCTs
Single RCTs
Non-randomized comparative studies
Cohort studies
Case-control studies
Non-comparative studies
Case Series (open trial)
Case reports
Expert opinion
What are synopses?
- Evidence-based journal abstracts and commentaries
- Summary of reviews or individual studies
- Easy to interpret & digest
- highly efficient
- detailed information readily available
Where to find Synopses?
- infopoems
- clinical evidence online
- bandolier
- evidence-based medicine
- therapeutics initiative
- ACP journal club
How to efficiently appraise ‘usable evidence’?
- right patient population (external validity)
- study design (right for the question)
- internal validity
- results (are they meaningful and useful? outcome measure? can they be applied to my clinical question?)
What is allocation concealment?
Happens before and during randomization.
Shields those who admit patients into a trial from knowing future assignments. The equal division for gender and age groups and other similarities are distributed equally by a computer - not by a person.
What is blinding?
Not always possible.
Happens after randomization.
Three groups to consider: patient, treatment team, treatment evaluator.
Could be double blinded or triple blinded.
Why is blinding important?
For subjective outcomes.
So patient don’t do other things to improve the outcome other than the one in the study.
What is p-value?
Probability of the data, or more extreme data, occurring in the long run when there is no treatment effect.
How often this result, or one more extreme, will occur by chance alone.
What does p=0.013 mean?
1.3% chance the difference was due to just chance
What can account for the difference for the p-value in the trial?
- a true difference
- bias
- confounding factors
- random error (chance)
- all of the above
What the p-value does not tell us?
- if the difference is valid
- if the difference is clinically meaningful
- if the difference is real
- if the drug/therapy works
What is considered a statistically significant p=value?
p=0.05 (it’s arbitrary and by convention)
What is Confidence Interval?
-quantifies the uncertainty in measurement: a measure of the precession of the “effect estimate” from the study.
How is Confidence Interval usually reported as?
95% CI
In a very large number of repetitions of the study, 95% of all CIs obtained will contain the “true” value of the treatment effect in the population studied (assuming random sampling).
What studies need p-value and CI?
Those who are not studying the whole population.
What does the CI tell us?
the +/- of where the results might lay. we have a range but not an exact result.
The wider the range, the less we know for sure.
How do you decide if its clinically significant?
The magnitude of the difference - agreed before hand, and if you think it is.
Relative Risk Reduction (Relative numbers) (RRR)
Estimate of the percentage of baseline risk that is removed as a result of the new therapy. The problem with using RRR is that we cannot assess the actual effect size if the event rate in the control group is not known.
Useless unless you know the starting point. (a % of what?)
RRR Formula
(rate A - rate B) / rate A
or
ARR/rate A
ARR Formula
rate A - rate B
NNT
1/ARR
Absolute Risk Reduction (Absolute numbers) (ARR)
Risk difference.
The proportion of patients who are spared the adverse outcome as a result of having received the experimental rather than the control therapy.
Number Needed to be Treated (NNT)
The number of patients you need to treat to prevent one additional bad outcome (death, stroke, etc.)
Numbers Needed to be Harmed (NNH)
How many patients must receive a particular treatment for 1 additional patient to experience a particular adverse outcome.
When is ARR/NNT/NNH calculated?
Only when the result is statistically significant.
What is an effect size (ES)?
The magnitude of effect of a treatment.
When effect size is important?
When looking at several options for treatment on a disease.
ES Formula
(mean 1 - mean 2) / SD
SD=Standard Deviation