Chapter 3 - Types of Studies Flashcards
Are case control studies prospective, retrospective or both?
Retrospective.
About how many people show a placebo effect?
1/3
Why are anecdotes the weakest kind of evidence?
Some described effects could be due to anything, not necessarily a particular treatment. There are no controls. Most medical conditions get better anyway by themselves. Bias or expectation can influence reporting.
Anecdotes
Personal communications, the weakest type of evidence.
Types of bias that can be found in clinical trials
Failed trials aren’t published, trial details left out of publication, invalid comparisons can be made, effects can be misrepresented, and side-effects can be minimized.
Epidemiology
study of disease within populations
Publication bias
When positive results are more likely to be published than negative ones.
Case studies
Report on one patient’s symptoms, signs, diagnosis, treatment, and follow-up. Usually describes a novel or unusual occurrence.
What factors associated with expectation can affect the placebo response?
Enthusiasm of the practitioner, larger pills, capsules (vs pills), injections (vs pills), colour, believing in the treatment.
Limitations of case studies
No control, sample size of only 1.
Limits of observational studies
The weakest of the scientific studies. Subjects not randomized into different groups. Show correlation at best.
Placebo pain relief is in part due to…
Opiate-receptors, and the release of dopamine.
How many papers in CAM journals report negative results?
Only 1-5%
Prospective
looks into the future
What can be learned from post-marketing surveillance?
What the rare adverse effects and long-term adverse effects are.
Unique problems of testing CAMs.
Unethical to test a treatment against one already shown to work. Difficult to blind. Treatments may be patient specific.
Is it ethical for a doctor to use a placebo to diagnose if a patient’s symptoms are real?
No, and it’s misguided.
What is the placebo effect important?
it may be the real cause of a positive result from some studies (especially those with poor controls).
What features should interventional studies have?
Placebo controlled, randomized and double-blinded.
Gold standard treatment
most commonly used treatments
Placebo effect
The perceived or actual improvement of a medical condition after receiving a sham intervention.
Nocebo reaction
A negative placebo reaction.
3 categories of scientific medical studies
- observational studies. 2. interventional studies. 3. summaries of other studies.
Phase III clinical trials
300-3000 participants. Randomized. Compares treatment to existing ‘gold standard’ treatment.
Phase II clinical trials
20-300 patients who are targets of the drug. Determines how well the drug works. Continues safety assessment.
Case series
Follows a group of subjects with a similar exposure and examines the outcome.
Perks of case control studies
Fast an inexpensive.
The most powerful type of evidence
Meta-analysis and systematic reviews.
Safety issues with CAM
Sometimes they’re really dangerous. Wasting time in treating a serious condition. May interact negatively with conventional treatments. 1/2 of patients do not tell their doctors they use CAM. Waste of money.
Retrospective
looks backward
Systematic reviews
Collect and critically analyze multiple research studies or papers
Phases of OM treatment testing
Pre-clinical (in vitro); phase I; phase II; phase III; phase IV (post marketing surveillance).
Results of many CAM studies are confounded by…
Placebo effect, regression fallacy, improper initial diagnosis, treatments improperly described, lack of randomization, lack of double blinding.
Criticisms of many CAM studies
Anecdotal evidence, small sample sizes, and inadequate controls.
Case control studies compare subjects who…
have a condition/disease with subjects who do not have that condition/disease, but are otherwise similar.
Efficacy
how well something works in a trial
Case control studies
Used to identify factors that may contribute to a medical condition. Not an experiment. Typically involve large numbers of people. Often used in epidemiology.
Meta-analysis
combines the results of several randomized, controlled studies and re-analyzes them using statistics, in order to increase statistical power to detect a treatment effect.
Are case series prospective, retrospective or both?
Can be both prospective and retrospective.
Limitations of case series
No control. Prone to selection bias, may not represent the wider population.
Why is private funding of CAM research unlikely to be economical?
Most CAM treatments aren’t patentable. In many countries there is no incentive to do so
Cochrane
Non-profit group that promotes evidence-informed health decision-making by producing high-quality, relevant, accessible systematic reviews and other synthesized research evidence.
Regression fallacy
The condition was going to go away on its own anyway, but the ‘treatment’ is given the recognition of ‘curing’ the disease.
Interventional sutides
compare treated subjects to those who receive a control or standard treatment.
Effectiveness
how well something works in the real world.
Types of observational studies
Case series/reports, case-control studies, and cohort control studies.
Weakness of case control studies
Can only show correlation between treatment and outcome. Not direct evidence of cause and effect.
What is the most common stage of failure for new drugs?
Phase II
In what kind of trials is the placebo effect the weakest?
Well done trials that are measured by a third person.
Phase I clinical testing
Small groups (20-100 healthy human volunteers); inpatient (at hospital); paid for time. Tests for safety and effective dose.
