Clinical trials Flashcards
What is confounding?
when variable is related to both the study variable and the outcome so the effect of the study variable on the outcome is distorted
What is a clinical trial designed to do?
measure the effectiveness of an intervention i.e. a new drug
they are different to epidemiological studies which are typically observational
Why is a control group necessary?
or else you cannot be sure why the outcome happened
could be due to new treatment or may have happened anyway
Why is randomisation important?
ensure balance
to avoid/remove treatment bias as it is possible the investigator will choose different patients for each group
What types of randomisation are there?
block
stratification
minimisation
What is blinding?
patient does not know whether receiving treatment or not
What is double blinding?
patient nor doctor knows who receives treatment
Why is blinding used?
prevent bias in reporting or measurement of outcome, measurement bias
people receiving new treatment often report improvement in symptoms due to enthusiasm or hope
or doctor may look for more improvements
Why ethics and consent of clinical trials important ?
clinical trials strictly regulated to ensure patients are protected
All clinical trials must be…
Registered
Reviewed by independent scientific committee
Approved by Research Ethics Committee
Adhere to governmental and international guidelines
What do all trials have?
Independent data monitoring committee who are independent researchers that can check progress during the trial
they un-blind results to see if major difference present between intervention and control groups - if there is, they can stop trial
What must participants of trial provide?
informed consent
free to withdraw at any time without affecting their care
What is efficacy?
true biological effect of treatment
What is effectiveness?
effect of treatment when used in normal practice
What is the EER (experimental event rate)?
incidence in intervention arm
What is the control event rate (CER)?
incidence in control arm
Relative risk?
EER/CER
Relative reduction?
CER-EER/CER
Absolute risk reduction (ARR)?
CER-EER
Number needed to treat (NNT)?
1/ARR
What guidelines are used when reporting clinical trials?
CONSORT
consolidated standards of reporting trials
Ensures that papers about trials include all information for readers to critically appraise the paper
Phase I CT?
test safety of new treatment
- side effects
- small no of healthy volunteers
Phase II CT?
- test in larger group with disease to see if treatment is promising (effective in short term)
- few hundred
- assess safety
Phase III CT?
- test in larger group of people
- compare with current treatment/placebo
- assess how well new treatment works, side effects
- several thousand
- patients recruited from multiple locations including several different countries
- if expected advantage is small more people needed to take part
Phase IV trial?
after drug/treatment has been marketed to gather information on the drugs effect in various populations and side effects with long-term use
