lecture 5 Flashcards
What is the 4 bottom hierarchy of evidence?
4- Cohort studies
5- Case- control studies
6- Cross -sectional studies
7-Case reports
What are the bottom four hierarchy evidence called?
Observational studies
Apart from observational studies what other studies is part of the hierarchy system ?
Experimental studies
What other name is given for experimental studies?
Clinical trials
What does a clinical trial consist of?
Treatment group and control group
What is the difference between experimental and observational studies?
Observational studies have confounding
Experimental studies have no confounding
What if there is no control group?
Dummy control
What is the importance of a control arm?
you have a control group
What alternative trial is there?
Cross over trial
What does a cross over trial consist?
Two experiment periods separated by ‘wash out’
What is the advantage of cross over trial?
Minimise variability
What is the disadvantage of a cross over trial?
Not suitable if effect carried over
- if experiment A works then it will not proceed to experiment B it will just stop
What types of clinical trials are there?
Phase 1 and phase 2
phase 3 and phase 4
What is phase 1 and phase 2 trails?
Safe trails that are carried out in animals as the agent is too toxic and not safe for humans
What is phase 3 trail?
Randomised treatment comparison- which sometimes can be used in random humans
What is phase 4 trail?
Post marketing surveillance which are tests carried out in humans - to know that a treatment works and want to know if it continues to work under different clinical regimes
In cross over trials what must be the same in each arm?
Subject on each arm must be the same
How do you make sure the subject on each arm are the same?
- Randomisation: random allocation
- Making them the same: reduce bias (volunteer bias)
- single blind or masked trial: placebo effect
- Assessor bias
- Double blind trail
What is volunteer bias?
Cannot select px- no volunteering in what treatment they get as it is random allocation - px is not ware of their treatment
What is the placebo effect?
dummy treatment given to the px to fool them
What is assessor bias?
Assesors can choose what treatment they want to give which px- assessors can often bias the results for other reasons
What 5 different ethical issues are there in clinical trails?
Numerous
Research and ethics committees
Declaration of helsinki
Informed consent: px must just receive placebo
Sample size- (too small or too large can be unethical)
What other issues are there?
> Non compliance ( intention to treat)
Publication bias (negatives finding not published)
Multi-centre trails (trails used in different hospitals)
Meta analysis- combining results from different trails- systemic reviews
What is non compliance ( intention to treat)
If they do not get treated results used as if they are treated
