7 - Clinical trials

Question 1

Definition of clinical trials

Answer 1

a planned experiment in humans, designed to measure the effectiveness of an intervention
intervention is usually a new drug, but the method can equally be applied to the assessment of a surgical procedure, a vaccine, complementary therapy etc
clinical trials are the ONLY experimental design in epidemiology
(because most epidemiological studies (surveys, cross sectional, cohort, case control, ecological) are observational)

Question 2

Bias definition

Answer 2

systematic error in design, conduct or analysis of a study which produces a mistaken estimate of treatment effect

Question 3

Confounding definition

Answer 3

When a variable (or factor) is related to both the study

variable and the outcome so the effect of the study variable on the outcome is distorted

Question 4

Features of a clinical trial

Answer 4

Experimental study
Must contain a CONTROL group
Prospective: participants are followed through time
Patients are enrolled, treated and followed over same period of time
Participants should be randomised to control or intervention groups
Ideally the participants and the researcher are unaware if a participant has been assigned to the treatment or control group = blinding

Question 5

control group

Answer 5

study participants who do not receive the intervention under assessment
control group must be included otherwise you cannot be sure why the outcome happened

Question 6

purpose of randomisation

Answer 6

to remove treatment ALLOCATION BIAS

Question 7

double blind trial

Answer 7

neither the patient nor the doctor knows which treatment they are getting ->
prevents bias in reporting or measurement of the outcome, MEASUREMENT BIAS

Question 8

outcomes are presented in terms of…

Answer 8

efficacy

effectiveness

Question 9

efficacy definition

Answer 9

true biological effect of a treatment

Question 10

effectiveness definition

Answer 10

effect of a treatment when actually used in “normal” practice

Question 11

experimental event rate (EER)

Answer 11

incidence in the intervention arm

Question 12

Control event rate (CER)

Answer 12

incidence in the control arm

Question 13

Relative risk

Answer 13

EER/CER

experiment / control

Question 14

Relative reduction

Answer 14

(CER- EER)/ CER

Question 15

Absolute risk reduction (ARR)

Answer 15

CER- EER

Question 16

Number needed to treat (NNT)

Answer 16

1/ARR

Question 17

Phases of clinical trial

Answer 17

Phase I to IV

to ensure safety and effectiveness of drug

Question 18

Phase I

Answer 18

tests safety of new treatment
looks at side effects
usually, small group of healthy volunteers

Question 19

Phase II

Answer 19

tests new treatment in a larger group of people who have the disease for which the treatment is to be used, to see whether the treatment is promising
effective at least in the short term
a few hundred people are involved at this stage
also tests safety

Question 20

Phase III

Answer 20

test new treatment in a larger group of people
compare new treatment with treatment currently in use, or with a placebo
look at how well new treatment works, and at any side effects it may cause
several thousand patients will be involved
Patients will be recruited from multiple locations and this might include several different countries
The smaller the expected advantage of a treatment, the more people will be needed to take part in a trial

Question 21

Phase IV

Answer 21

done after the drug or treatment has been marketed to gather information on the drug’s effect in various populations and any side effects associated with long-term use

Question 22

Ethics

Answer 22

clinical trials should be:
regulated to ensure that patients are protected
registered, reviewed by an independent scientific committee
approved by a Research Ethics Committee
adhere to government and international guidelines

Question 23

What occurs before phases of clinical trial

Answer 23

laboratory stage

Question 24

process of laboratory stage

Answer 24

1) tissue samples
- computer stimulation
- other in vitro tests
2) animal testing
- mainly rodents
- tests for toxicity
3) MHRA and ethical bodies
- drug cleared for human testing