Summarized Resources Flashcards
What are the 4 A’s of evidence based medicine?
Ask, Acquire, Appraise, Apply
The highest level of evidence, the evidence that is most valid (free of bias)
“Best” Evidence
Biased samples, unrealistic methods, and Berkson’s bias all affect
External Validity
Bias from subjects or investigators, extraneous factors, and lack of randomization all affect
Internal validity
Synthesize results and pull together major findings
“Review” Articles
Review articles can be found in many
Clinical journals
The strength of review articles are that, if done well, they provide a good discussion from experts in the field on the most important findings and
New directions
What are the weaknesses of review articles?
They are subject to the bias of the author or the journal
Reviews of the literature that follow a prescribed protocol to remove bias
Systematic reviews
Save time and find and summarize the best evidence (When done well)
Systematic reviews
Provide up to date summary of all published research literature and allow large amounts of data to be assimilated
Systematic Reviews
Where do you find systematic reviews?
Peer-reviewed journals, or databases (Cochrane library)
Systematic reviews define a specific
Question
Find all scientific studies, select the strongest studies, and describe the scientific strength of the selected studies
Systematic reviews
In a systematic review, the specific question is defined using
PICO
Patient (population)
Intervention (exposure, test, or other agent)
Comparison (other treatment/group)
Outcome (outcomes of clinical importance)
You have a patient who is trying to lose weight and has decided to take up running, in hopes of running a marathon in the next year. She has a trainer, who recommends that she prevent muscle soreness by using a new whole-body cryotherapy machine that was bought by the gym. The trainer says it will prevent muscle soreness. She asks whether it would prevent muscle soreness, and whether it would be good for her. What is the PICO?
Patient = Adults Interventions = Whole-body cryotherapy Comparisons = Nothing, or other non-drug txs Outcomes = amount of muscle soreness
A 52 year old man reports to E.D. complaining of
worsening epigastric pain for 1 day with chronic
pain for 3 months. Nausea and vomiting for 1 day,
and no bowel movement for 1 day. History of
similar attacks increasing in frequency over the
past 3 years. Significant history of ongoing alcohol
abuse. No recent trauma. He is diagnosed with acute pancreatitis and says that he read that enteral feeding (tube feeding) may be better than the intravenous feeding. He asks you what you think. What is the PICO?
Patient = adult with severe acute pancreatitis Intervention = Enteral Feeding Comparison = IV feeding Outcome = Survival, disease severity, complications?
On her routine visit to assess her asthma control, Ms. S, your 23 year old patient with persistent asthma, says that she recently heard that drinking coffee makes asthma better. She normally takes asthma control medicine and uses an inhaler a few times a week when she has a severe episode. She would like to know if drinking more coffee will reduce her need to use her inhaler. What is the PICO?
Patient = Adult asthma patients Intervention = regular asthma medication plus coffee Comparison = regular asthma medication alone Outcomes = reduction in asthma symptomes and reduced use of inhaler
A large, multi-site study is published that examined the effectiveness of a new drug to promote hamstring muscle healing after a strain. 100 subjects from 10 sports medicine centers are chosen and randomly assigned to receive the drug or placebo. The drug was found to work and have an added benefit. What would be an example of an extraneous factor that would be important to control in order to increase the internal validity of the study?
Whether people in the drug group were using other forms of medication such as non-steroidal anti-inflammatories
In a systematic review, the purpose of finding all relevant studies and selecting the strongest studies is to get a
Representative sample
The goal to finding all the studies bearing on a question is to
Increase sensitivity and reduce bias
What are some methods to choosing the strongest articles?
Limit to RCTs and avoid observational trials, or those without a comparison group
You should always include unpublished studies to avoid
Publication bias
Bias towards publishing only positive outcomes
Publication bias
A systematic review aims at examining internal validity by reviewing for bias and making sure the review includes more than one
Researcher
Determining the scientific strength of the selected studies and if quality is associated with results is how systematic reviews examine
Internal validity
Weaker studies tend to have better
Effect sizes
In a Forest-plot, the size of the square is proportional to the
Number of people in the sample
In a Forest-plot, the line length represents the
CI (larger means more variability/error)
If results are similar, they can be pooled and analyzed together in a
Meta-analysis
Pooled results are weighted by sample size. What are the two models?
Fixed effect model and random effect model
When studies ask the same question
Fixed effect model
Assumes studies are asking different questions but are somewhat similar
Random effect model
