1.2 Clinical Trials Flashcards
What are confounding factors?
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
What is the definition of a clinical trial?
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
What is efficacy?
The ability of a health care intervention to improve the health of a defined group under specific conditions
What is the difference between efficacy and effectiveness of a drug?
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
What is safety?
The ability of a health care intervention not to harm a defined group under specific conditions
In a study, how can you decide who should and shouldn’t take part?
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
What is the problem with doing multiple outcome measures?
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
What is the purpose of a primary outcome measure?
Hopefully only get one and you can use it in your sample size calculation
What is the purpose of secondary outcomes?
Other outcomes of interest, often includes occurrence of side effects
What are the types of outcomes?
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
What are the features of an ideal outcome?
- 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
What outcomes would you want to get in a study
E.g comparing the taste between two different chocolate bars
Primary outcome: Taste
Secondary outcome: texture
How can we insure comparability between groups in a study?
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
What three things does a clinical trial need to be to give a fair comparison of effect and safety?
Reproducible - in experimental conditions
Controlled - comparison of interventions
Fair - unbiased without confounding
What do non randomised clinical trials involve?
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
What does random allocation/ randomisation result in in terms of the data collected?
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
How can we do randomisation?
Toss a coin, random number tables
What is the advantage of blinding in data collection?
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
When is blinding difficult?
Surgical procedures Psychotherapy vs anti depressant Alternative medicine e.g acupuncture vs western medicine’ Lifestyle interventions Prevention programmes
What is how can bias affect results?
- selection
- outcome measured by patient/doctor/researcher
- publication bias
How does randomisation and blinding affect bias?
Good randomisation eliminates selection bias
Blinding reduces outcome measurement bias
What steps are involved in the conduct of a trial?
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
What is the point in comparing a no treatment group to a treatment
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
What is the placebo effect
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
What is a placebo
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
What are the ethical implications of a placebo?
Use is a form of deception. Therefore, its essential that participants in a placebo controlled trial are informed that they may receive a placebo
How can you minimise losses to follow up?
- make the follow up practical and minimise inconvenience
- be honest about the commitment required from participants
- avoid coercion or inducements
- maintains contact with participants
Why may a matinee not comply with treatment and how can you help improve this?
- misunderstood instructions
- don’t like taking treatment
- think its not working
Improve by…
- helping them understand
- ask about adherence
- monitor adherence
