13. Epidemiological studies – experimental studies Flashcards
What is an experimental study?
always an experimental and
control group. The investigator controls the exposure, often in
a randomized way.
- What are
intervention trials?
- An intervention trial is a follow-up experimental study in which the exposure under investigation is applied by the investigator.
- The aim of intervention trials is to investigate a possible causal relationship by exposing one or more groups of patients
to a factor (treatment) and compare results to one or more control groups that are unexposed to this factor. - In an intervention trial, the investigator decides which subjects are to be “exposed” and which not, so in epidemiology, intervention trials are the closest analogy of a
laboratory experiment.
Types of interventions:
Prophylactic - target on prevention (e.g. vaccines)
Diagnostic - target on evaluation of new diagnostic procedure
(e.g. new lab test to a gold standard, etc.)
Therapeutic - target on treatment (e.g. new drug)
types of control groups
Placebo concurrent control group Dose-response concurrent control group Active concurrent control group No treatment concurrent control group Historical control (ask mahds to explain each one if needed)
Intervention trials can be:
community trials
clinical trials
lab experimental trials
Community trial
a research study, carried out in a realistic
community setting, that can involve an individual-leve
clinical trials
– a research study to test new methods of
screening, prevention, diagnosis or treatment of a disease,carried out in hospital settings;
lab experimental trials
a research study, usually carried out on animals or tissues in laboratories.
What are clinical
trials?
Clinical trials can be randomized controlled studies or nonrandomized studies (quasi-experiments).
Randomized clinical trial (RCT)
is a prospective study that
estimates the effect of an intervention by comparing participant outcomes between randomly assigned treatment and control groups.
- RCT are the gold standard for development of new drugs.
how many phases does Randomized clinical trials have
4
phase 1
an early study to determine the non-toxic dose level in animals or small group of health volunteers.
phase 2
- designed to assess the clinical efficacy of the therapy
2a - assess dosing requirements
2b - study efficacy
phase 3
– designed to confirm the effectiveness, monitor side effects and compare to other treatments alternatives.
phase 4
– designed to detect any rare or long-term adverse
effects over a much larger population and timescale.
advantages of interventional trials
Provide strongest evidence for causality
Can investigate several outcomes from one exposure
Less susceptible to errors due to observer, subjectivity and technical issues
Disadvantages of interventional trials
Costly and time consuming
Lost to follow-up cause selection bias
Ethical problems
Single ascending dose studies :
: groups of several patients are given small doses and monitored for side effects. Ig no major side effects are present another set of groups are given a higher dose. This is continued until the side effects are intolerable. This is when the drug has reached maximum tolerated dose - MTD
MULTIPLE ASCENDING DOSE STUDIES :
: group of patients receive a low dose and dose is subsequently escalated up to a predetermined level. Better example of pharmacokinetics and dynamics.
Randomized
method of allocation of the patient to 2 or more treatment options where each patient has an equal chance of receiving each treatment.
Blinding
- method to assure subject and investigator or outcome. Assessor is unaware of assignment.
placebo def
pharmaceutical substance - no active ingredient.
