Understanding published evidence from human experiments Flashcards
What is the purpose of an abstract in a paper?
- Outlines aims of study
- Participants
- Results/data
- Conclusions
- Will results change clinical practice
What is meant by ‘prospective’?
When individuals are followed up, eg. a health outcome is followed up after a period of observation
What is meant by a randomised controlled trial?
- A human exp, in which an intervention is administered to humans in order to evaluate its efficacy + safety - AKA experimental or intervention study
- It is not purely observational, we have intervened by allocating participants to treatment (eg. propranolol) or control group
- We observe how participants respond to the intervention
What is the control group?
- Control group can receive either usual care/treatment or placebo
- Appearance same as treatment
What is the placebo effect?
Cure or alleviation of symptoms following an intervention which the patient believes to be effective against the ailment, but which, in fact, is completely neutral.
Such effects seem to be based on the person’s self-healing capacity, which is triggered by the belief that they are receiving an active medication.
What is randomised allocation?
- Random allocation implies that individuals were allocated randomly to each study group
- And that each individual had an equal chance of being allocated to either group
What is the point of randomised allocation?
Ensures neither the observers nor the individual participating in the study can influence, by way of personal judgement or prejudice, who is allocated to receive which treatment.
What is a double blind trial?
Neither the patient nor observers know to which group patient was allocated
What is a single blind trial?
Either patients or observers do not know to which group a patient has been allocated
From the following data, how would you work out the (i) risk of dying in each group, the (ii) risk ratio/relative risk and (iii) interpret answer (ii)?
- Propranolol group (total 278) (total deaths 25)
- Placebo group (total 282) (total deaths 37)
- Propranolol risk = 25/278 = 0.0899
- 0899 x 100 = 8.99%
- Placebo risk = 37/282 = 0.1312
- 1312 x 100 = 13.12%
To work out relative risk (or risk ratio), you divide 8.99/13.12 to give 0.69, therefore the risk of death in the placebo group is 69% times higher the risk in the propranolol group.
What does it mean when the relative risk = 1?
That the two risks are the same, eg. if propranolol had no effect, you would get the same risk of dying in propranolol and placebo groups, so the risk ratio = 1!
What is meant by ‘Intention to treat’?
An assessment of the people taking part in a clinical trial, based on a group they were initially (and randomly) allocated to, regardless of whether they dropped out or adhered to treatment.
“once randomized, always analyzed”
Intention-to-treat analyses are often used to assess clinical effectiveness because they mirror actual practice - not everyone adheres to the treatment, and the treatment people receive may be changed according to how their condition responds to it.
