EBP1 Week5 Material Flashcards
Narrative Reviews, SRs, MetaAnalysis and Diagnostic Studies
What are the three types of literature reviews?
narrative reviews, systematic reviews, meta-analysis
What is the purpose of a narrative review?
To summarize what is in the literature on a given topic, often written by experts which provide a good source of background info
Why are narrative reviews prone to bias?
They do not follow the strict systematic methods of review
During what phases in a literature study can bias be seen?
- Literature search 2. reporting of literature 3. Discussion and conclusion
What is the purpose of a systematic review?
rigorous process of searching, appraising, and summarizing the existing information on a topic, addressing effectiveness, accuracy, prognosis. Objective and transparent!
What is the process of a Systematic review? {10 steps]
- state objective 2. develop protocol 3. Develop search strategy 4. conduct the search 5. Retrieve relevant papers 6. Screen and select papers that meet established criteria. 7. Evaluate methodological quality 8. Analyze and synthesize findings 9. Determine if data is sufficient for further data 10. if not, report results of SR. If yes, meta-analyze then report
What is the purpose of meta-analysis?
Optional part of SR to extract and combine data to produce a summary results
When should a meta-analysis be completed?
- when more than one study has estimated effect 2. when no differences exist between study characteristics that are likely to affect outcome 3. outcome has been measured in similar ways
What is a common method of summarizing results of a meta-analysis?
Forest plot
Briefly describe a forest plot.
graph to illustrate the treatment effect sizes of the studies. Each is represented by a black square that is an estimate of the effect size. Confidence intervals are shown as horizontal lines around the estimate. these lines are graphed favoring control vs favoring intervention, separated by the center “risk line” (no difference in risk between the groups).
What is the diagnostic process?
Pattern recognition (History exam, physical exam) and logical reasoning
What is the test threshold?
The probability below which a diagnostic test will not be performed because of the possibility of diagnosis is so small
What is treatment threshold?
The probability above which a diagnostic test will not be performed because the possibility of diagnosis is so great that immediate treatment is indicated
What is the pretest probability of a diagnostic test?
what we might think the problem may be before testing (based on intuition and experience of clinician)
What is the posttest probability of a diagnostic test?
What we think the problem is now that we know the test result
What is the basic structure of a diagnostic study?
Take a series of patients and give them an index test. Then give them a reference “gold” standard. then compare the results between the two
What is the typical shape design of a diagnostic study?
2x2
What are the two axes of a diagnostic study design?
Index test vs gold standard
What are the four possible results?
A, true positive. B, False positive. C, false negative. D, True negative.
What are some commonly used gold standards?
Radiography, surgical exploration, a previous consistent and useful test
What are ways to minimize bias of a diagnostic study?
- To blind the assessors - each assessor is blind to the others’ results. 2. Ensure that their is a spectrum of patients within all levels/stages of the disorder 3. ensure all subjects underwent both tests
What type of bias is the lack of heterogenity?
spectrum bias
What type of bias is the lack of all patients receiving both tests?
Workup/Verification bias
What is the proportion of people in a study that HAVE the disease who had a POSITIVE test result?
Sensitivity
What is the formula for sensitivity?
True positive/ true positive + false negative
A high sensitivity helps _ _ a condition.
rule out
What is the proportion of people in a study that DO NOT HAVE the diseases who had a NEGATIVE result?
Specificity
What is the formula for specificity?
True negative/true negative+false positive
A high specificity helps _ _ a condition.
Rule in
What is the likelihood that a person who test positive actually has the disease?
Positive predictive value
What is the formula for positive Pv?
True positive/ true positive+false positive
What is the likelihood that a person who tests negative is actually free of the disease?
Negative predictive value
What is the formula for negative PV?
True negative/ True negative+false negative
What is used to mathematically combine specificity and sensitivity?
Likelihood Ratios
When would you use a positive likelihood ratio? negative?
If the diagnostic test is positive, if the dx test is negative
What is the formula for a positive likelihood ratio?
Sensitivity/ (1-specificity) (true positive/false positive)
What is the formula for a negative likelihood ratio?
(1-sensitivity)/specificity (false negative/true negative)
What positive likelihood ratio range indicates a large, conclusive importance? Negative?
> 10 , <0.1
What positive likelihood ratio range indicates a moderate importance? Negative?
5-10, 0.1 - 0.2
What positive likelihood ratio range indicates a small, sometimes important effect Negative?
2-5, 0.2-0.5
What positive likelihood ratio range indicates a small, rarely important effect?
1-2, 0.5 to 1
What likelihood ratio value indicates a useless test?
1 (true=false)
If a +LR has a 95% confidence interval resulting in 5.6, what is the usefulness/importance?
Moderate importance = test is pretty helpful
If a +LR= 3.75 and a -LR of 0.76, what is the usefulness/importance?
Potentially helpful in a positive test but unimportant in a negative test
What are tools that quantify the contributions pf different variables to the diagnosis, prognosis, or likely response to treatment for an individual patient?
Clinical Prediction Rule
What is the purpose of a CPR?
To reduce uncertainty by identifying clusters of clinical findings and using them to predict outcomes
What are CPRs helpful in use for?
Diagnosis, Prognosis, Response to Intervention
Why is it important to validate CPRs?
To establish the significance and make sure it works among other populations and not just the one cohort
How do you validate a CPR?
Take a rule and apply it to the population of intent, follow the population forward and measure the outcomes (Diagnostic or prognostic) and evaluate: is it narrow/diverse? internal/external?
What is the final step in acceptance of a CPR?
Impact Analysis
What is the purpose of an impact analysis?
Ensuring the CPR works in the real world - does it do what it was intended to do? Does it benefit? Is it usable?
