Clinical Trials Flashcards
Clinical trial
Planned experiment in HUMANS, designed to measure effectiveness of an intervention
How do clinical trials differ from observational studies?
Observational studies- investigator measures what happens but does not control it.
Clinical trial- investigator chooses who does what
Features of a clinical trial
Experimental
Must contain a control group
Prospective
Participants randomised & followed over same period of time
What must a clinical trial contain?
Control group
Why must a clinical trial contain a control group?
If not included, you wouldn’t know why the change happened as too many variables
Why randomise in a clinical trial?
Removes treatment allocation bias
What is Blinding?
patient does not know whether they are getting the new treatment or not.
What is double blinding?
neither patient nor doctor knows which treatment they are getting.
Ethics in a clinical trial
Registered & reviewed by an independent scientific committee
Independent data monitoring committee
Patients provide informed consent & can withdraw at any time
Experimental event rate (EER)
Incidence in the intervention arm
EER Equation
𝐷𝑖𝑠𝑒𝑎𝑠𝑒 𝑒𝑣𝑒𝑛𝑡 / 𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑖𝑛𝑡𝑒𝑟𝑣𝑒𝑛𝑡𝑖𝑜𝑛 𝑔𝑟𝑜𝑢𝑝
Control event rate (CER)
Incidence in the control arm
CER Equation
𝐷𝑖𝑠𝑒𝑎𝑠𝑒 𝑒𝑣𝑒𝑛𝑡 / 𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑐𝑜𝑛𝑡𝑟𝑜𝑙 𝑔𝑟𝑜𝑢𝑝
Relative risk equation
EER / CER
Relative risk reduction equation
(CER- EER) / CER
Relative risk reduction
% decrease of incidence between interventions compared to control
Absolute risk reduction (ARR)
absolute reduction in incidence of disease between intervention & control.
ARR Equation
CER- EER
Number needed to treat (NNT)
Average number of patients who need to be treated to prevent 1 additional bad outcome
Inverse of ARR
NNT Equation
1 / ARR
What is the ideal NNT?
1 : where everyone improves with treatment & no one improves with control.
The higher the NNT
The less effective is the treatment.
Clinical trials are reported according to
CONSORT guidelines
Clinical Trial Phase 1
Aims to test the safety & ensure there are no adverse side effects of a new treatment
Small No. of healthy humans
Clinical Trial Phase 2
Tests whether new treatment is effective against illness it was designed for
Small sample of humans with relevant illness
Clinical Trial Phase 3
Compare the new treatment with the treatment currently in use, or with a placebo. Look at how well the new treatment works, & at any side effects it may cause
Provides large sample size of analysable data
Large sample of humans with relevant illness
Clinical Trial Phase 4
Trials are done after the drug or treatment has been marketed to gather information on the drug’s effect in various populations & any side effects associated with long-term use
Tests side effects when used alongside other common drugs
