Introduction to Evidence Based Medicine Flashcards
The father of westernized medicine
-Questioned the idea that gods caused illness and disease
Hippocrates
A prominent example of how scientific findings are not always accepted
Pellegra
In the early 1900’s Pellegra was contracted by over 100,000 Americans, mainly in the deep south. What are the symptoms?
The 4 D’s
- ) Diarrhea
- ) Dermatiti
- ) Dimentia
- ) Death
Mostly seen in hospital for insane persons, orphanages, prisons, and very low income areas
-Attributed to a microbial infection
Pellegra
Worked in the US department of hygiene and was the first to postulate that Pellegra was due to dietary deficiencies. But his results were not accepted
Dr. Joseph Goldberg
In the 1920’s it was demonstrated that Pellegra was caused by
Niacin (Vitamin B3) Deficiency
Demonstrated that stomach ulcers were caused by a bacterial infection from Heliobacter pylori in 1984. But their results were not accepted until 1997.
-Won nobel prize in 2005
Barry Warren and J. Robin Marshall
What are five types of medical evidence?
- ) Diagnostic Studies
- ) Prognostic Studies
- ) Treatment Studies
- ) Prevention Studies
- ) Etiology Studies
Ask, “how sure can I be that a patient has a diagnosis?”
Diagnostic Studies
Ask “What should this patient expect following this surgery, this exposure, this diagnosis?”
Prognostic Studies
Asks “What are the causes or risk factors for the condition?”
Etiology Studies
When an old treatment is tested, and the results find that the treatment makes the patient no better, or no worse
Reversal
When a new treatment is tested and the treatment is found to be beneficial
Replacement
The conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients
Evidence Based Medicine (EBM)
Who originated evidence based medicine?
-designed the first randomized control trial (RCT)
Sir Bradford Hill
According to Archie Cochrane (1971) an intervention is only “effective” if it has been demonstrated, preferably by a RTC to
Do more good than harm
Anything that has an “effect” can also have
Side effects and risks
Out of 100 children with strep throat,
86 correctly detected w/ the rapid tes
-14 will be missed
Out of 100 children with non-strep sore throat
95 will be correctly classified w/ the rapid test
-5 will be misdiagnosed
What are the five A’s that evidence-based medicine includes to access the medical literature and determine its relevance to the patient?
Ask, Acquire, Appraise, Apply, Assess
“POEMS” are patient oriented outcomes that matter. They encompass the 5 D’s, which are?
Death, Disease, Discomfort, Disability, Dissatisfaction
Addresses areas of uncertainty and change in medical practice
Evidence-based medicine
All the people in a defined setting or with certain defined characteristics that the researcher is interested in
Population
The subjects from the population who are studied
Samples
The goal of clinical research is to generalize the results to the rest of the
Population of interest
The confidence with which the results can be accurately generalized to the population
External validity
A representative sample looks like the
Population
Are non-representative samples that decrease external validity
Biased Samples
To get a more representative sample, we want
Larger sample sizes
Identify who will be in the study
Inclusion criteria
Makes the sampling more manageable, controls variability (improving internal validity), and limits generalizability (external validity)
Inclusion and Exclusion criteria
When each member of the population has an equal chance to be included in the research
Probability sampling
The most common form of probability sampling
Simple random sampling
To ensure that critical variables are represented in the sample, subjects are stratified by traits and then randomly sampled
Stratified random sampling
A type of random sampling done when subjects are ordered.
-For example, the 3rd person from each letter of the alphabet can be chosen
Systematic sampling
Systematic sampling can incorporate stratification if there is a
Meaningful order
Non-probability sampling methods do not involve random selection. Three examples are
Purposive sampling, convenience sampling, and quota sampling
Hand-picking patients
Purposive sampling
People are chosen based on availability of volunteering
Convenience sampling
Convenience sampling with specific quotas included. This is like stratified sampling
Quota sampling
Factors or attributes in a research study that can have different values (ex: occupation, height, BMI, etc)
Variables
Variables that can be manipulated by the researcher
Independent variables
Measured outcomes. These may be “primary endpoints” or “secondary endpoints” in a study, aka: response variables or outcome variables
Dependent variables
In a study that seeks to determine if a drug works to relieve pain, what is the
- ) Independent variable?
- ) Dependent variable?
- ) Drug: Drug has 2 levels, drug and no drug
2. ) Pain reliefe
Other variables in the study that may affect the relationship between the independent and the dependent variables
Extraneous variables
If researchers wanted to examine whether relaxation therapy was better than drug therapy for reducing the number of tension headaches in medical students, what would be some extraneous factors to control or account for?
Diet, other medications, severity of headaches
A process at any stage of interference tending to produce results that depart from the true values
Bias
Occurs when comparisons are made between non-equivalent groups
Selection Bias
When extraneous factors, selection bias, or measurement bias occur, a study is
-A fatal flaw in research
Confounded
Occurs when the methods of measurement are dissimilar among groups of patients
Measurement bias
Occurs when two factors are associated (travel together) and the effect of one is confused with or distorted by the effect of the other
Confounding
The variation in the measurements that occurs for any reason
-expressed as spread in the data
Random Error (Chance error)
How can we limit the random error?
Limit the population, improve the measurements, and control the testing environment
The internal health of the study, i.e. how free it is from bias and chance
Internal validity
The degree to which you can generalize the results of the study back to the population of interest
External validity
If you wanted to study grade school kids, and you wanted to be absolutely sure you got a representative sample from each grade level, you would use
Stratified sampling (i.e. take a SRS from 1st grade, then 2nd grade, then 3rd, and so on)
Used less in clinical studies, but more in epidemiology studies
Probability sampling
Seen often in a qualitative study
Purposive sampling
If two groups you are studying have different diets or different types of headaches, or differ in any way, this is an example of
Selection bias
If extraneous variable are not controlled,they result in
Confounding
