PAS - Clinical Trials Flashcards
importance of a control group?
comparison group as some patients (2ithout treatment) will get better by themselves
importance of a placebo control group?
take account of ‘placebo effect’ = the benefit
obtained from receiving apparently helpful
treatment, even if the treatment has a neutral effect
importance of random allocation for intervention and control groups?
- ensures characteristics of patients in both groups are similar/ well-matched
- avoids allocation bias
- any differences in health outcomes at the end of trial ensured to be due to the intervention
what is blinding? types?
individuals kept unaware of which treatment
group participants have been assigned to
single blind - patient or assessor is blind
double blind - patient & assessor are blind
importance of blinding?
avoids selection and assessor bias from assessors, keeps them objective
avoids selection and response bias from participants, can affect compliance & completion of the trial
three key features of clinical trials
random allocation - minimises bias from participants and assessors, ensures differences between groups are due to the intervention
control group - doesn’t receive intervention, serves as a comparison group
blinding - keeping patients/ assessors/ researchers unaware of which participants are receiving the treatment, helps minimise bias & treatment effects
cross-over trial design?
participants receive multiple interventions sequentially - each participant acting as their own control
experimental treatment is received for a period of time, followed out by a washed out period, then the control treatment = these periods can be switched around
advantages of a cross-over trial design?
need less participants - participants are their own controls
within-individual comparisons can be made instead of between-individuals
disadvantages of a cross-over trial design?
can’t be used to assess treatment with prolonged effects
disease may not remain stable over trial period
more burden on participants, longer trial period, potentially more drop-outs
parallel trial design?
participants assigned to a single treatment group for the duration of the trial
each group receives a different intervention or dosage = outcomes compared at the end of the study period
compare intention-to-treat (ITT) analysis vs per-protocol analysis
ITT = analysis includes all participants involved, regardless of their groups and whether they received/completed the intended treatment
- more realistic estimate of effectiveness of the intervention in the real word
per-protocol = analysis includes only participants who completed the study according to the protocol
- more insight into efficacy of treatment under ideal circumstances
- can introduce bias with differing dropout rates between groups
relative risk?
compares the risk of an event occurring in the treatment group to the risk in the control group
RR = 1 - indicates no difference between groups
- RR > 1 = higher risk in treatment group
- RR< 1 = higher risk in control group
absolute risk difference?
represents the absolute reduction in risk associated with the treatment
calculated by subtracting the risk in the control group from the risk in the treatment group
number needed to treat?
inverse of absolute risk difference - the number of patients you need to treat to prevent one additional bad outcome
lower NTT = fewer patients need to be treated to achieve one additional positive outcome = more effective treatment
