1.2 Clinical Trials

Question 1

What are confounding factors?

Answer 1

Factors that can influence the outcome of a result e.g age/sex/other bias

Confounding = a situation in which a measure of the effect of an intervention on an outcome is distorted by the association of that intervention with other factors that influence that outcome

Question 2

What is the definition of a clinical trial?

Answer 2

Any form of planned experiment which involves patients and is designed to elucidate the most appropriate method of treatment for future patients with a given medical condition

Question 3

What is efficacy?

Answer 3

The ability of a health care intervention to improve the health of a defined group under specific conditions

Question 4

What is the difference between efficacy and effectiveness of a drug?

Answer 4

Efficacy = in gold standard conditions, the best given effect of a drug. What drug companies focus on.

Effectiveness = more realistic, set in the real world. More interested in this

Question 5

What is safety?

Answer 5

The ability of a health care intervention not to harm a defined group under specific conditions

Question 6

In a study, how can you decide who should and shouldn’t take part?

Answer 6

You need to create inclusion and exclusion criteria

E.g if its between two types of chocolate bars and seeing which one is better

Exclude - people with allergies/diabetics
Include - people who like chocolate

Question 7

What is the problem with doing multiple outcome measures?

Answer 7

The more things you test, the more likely you are to find something. You’d rather find one thing as your primary outcome.

So if this intervention has this effect and this effect only, its good.

If it has lots of different outcomes, its not good

Question 8

What is the purpose of a primary outcome measure?

Answer 8

Hopefully only get one and you can use it in your sample size calculation

Question 9

What is the purpose of secondary outcomes?

Answer 9

Other outcomes of interest, often includes occurrence of side effects

Question 10

What are the types of outcomes?

Answer 10

Patho-physiological
E.g tumour size, thyroxine levels and other biomarkers

Clinically defined
E.g death, disease and disability

Patient focused
E.g quality of life, psychological well being, social well being and satisfaction

Question 11

What are the features of an ideal outcome?

Answer 11

• appropriate and relevant to patient/clinician/society etc
• valid and attributable
• sensitive and specific: can detect changes accurately
• reliable and robust: if it was redone, you’d get similar results
• simple and sustainable: easily carried out repeatedly
• cheap and timely: not excessively expensive to measure

Question 12

What outcomes would you want to get in a study

E.g comparing the taste between two different chocolate bars

Answer 12

Primary outcome: Taste

Secondary outcome: texture

Question 13

How can we insure comparability between groups in a study?

Answer 13

By collecting baseline data on characteristics that may relate to both the condition and the outcomes we are investigating

E.g gender, age.

If its about what type of chocolate bar people prefer, others could include hunger

Question 14

What three things does a clinical trial need to be to give a fair comparison of effect and safety?

Answer 14

Reproducible - in experimental conditions
Controlled - comparison of interventions
Fair - unbiased without confounding

Question 15

What do non randomised clinical trials involve?

Answer 15

The allocation of patients receiving a new treatment to compare with a group of patients receiving the standard treatment

However
Can get
- allocation bias by patient, clinician or investigator
- confounding, both known and unknown

Causing unidentifiable differences between the treatment groups being compared

Question 16

What does random allocation/ randomisation result in in terms of the data collected?

Answer 16

Minimal allocation bias - randomisation gives each participant an equal chance of being allocated to each of the treatments in the trial

Minimal confounding - in the long run, randomisation leads to treatment groups that are likely to be similar in size and characteristics by chance

Question 17

How can we do randomisation?

Answer 17

Toss a coin, random number tables

Question 18

What is the advantage of blinding in data collection?

Answer 18

Remove allocation bias - by ensuring that randomisation gives each participant an equal chance of being allocated to each treatment in the trial

1) Single blind, double blind and triple blind

Depending on how many people out of the patient, clinician, assessor don’t know the treatment allocation

Question 19

When is blinding difficult?

Answer 19

Surgical procedures
Psychotherapy vs anti depressant 
 Alternative medicine e.g acupuncture vs western medicine’
Lifestyle interventions 
Prevention programmes

Question 20

What is how can bias affect results?

Answer 20

• selection
• outcome measured by patient/doctor/researcher
• publication bias

Question 21

How does randomisation and blinding affect bias?

Answer 21

Good randomisation eliminates selection bias

Blinding reduces outcome measurement bias

Question 22

What steps are involved in the conduct of a trial?

Answer 22

Identify eligible patients
Invite them to be in the trial 
Gain consent
Allocate participants to the treatment fairly
Follow up participant in identical ways
Minimise losses to follow up 
Maximise compliance with treatments

Question 23

What is the point in comparing a no treatment group to a treatment

Answer 23

The effect of comparing a new treatment group with a group receiving no treatment is to lessen one unsure as to whether any observed difference was due to the new treatment or to the fact that the group was receiving care

Question 24

What is the placebo effect

Answer 24

Even if the therapy is irrelevant to the patients condition, the patients attitude to his or her illness and indeed and the illness itself, may be improved by a feeling that something is being done about it

Question 25

What is a placebo

Answer 25

An inert substance made to appear identical in every way to the active formulation with which it is to be compared e.g appearance, taste, texture, dosage, regimen, warnings etc.

The aim of a placebo is to cancel out any placebo effect that may exist in the active treatment

Question 26

What are the ethical implications of a placebo?

Answer 26

Use is a form of deception. Therefore, its essential that participants in a placebo controlled trial are informed that they may receive a placebo

Question 27

How can you minimise losses to follow up?

Answer 27

• make the follow up practical and minimise inconvenience
• be honest about the commitment required from participants
• avoid coercion or inducements
• maintains contact with participants

Question 28

Why may a matinee not comply with treatment and how can you help improve this?

Answer 28

• misunderstood instructions
• don’t like taking treatment
• think its not working

Improve by…

• helping them understand
• ask about adherence
• monitor adherence