Clinical Epidemiology-Evidence Based Medicine Flashcards

1
Q

What are the two options for summarizing clinical research evidence?

A

systematic (cochran collaboration)

narrative (linus pauling)

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2
Q

In regards to the two options for summarizing clinical research evidence which option is the strongest?

A

systematic

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3
Q

What are some differences in narrative and systematic reviews?

A

Systematic —> question: focused on clinical; sources: explicit search strategy; selection: criteria set up; appraisal: rigorous and critical; synthesis: quantitative ; Inferences: usually EBM
Narrative –> question: broad in scope; sources: not usually specified; selection: not usually specified; appraisal: variable; synthesis: qualitative; inferences: sometimes EBM

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4
Q

In general what is a traditional narrative review?

A

Expert summary of research evidence to make recommendations.
(take a broad based topic and review it but does have to be done by an expert)

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5
Q

What are some advantages to a traditional narrative review?

A

Can address broad-based topics by authors with experience

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6
Q

What are some disadvantages to a traditional narrative review?

A

Lack of structure, potential for value judgements, biases.

therefore may not be the most valid method

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7
Q

What is a systematic review?

A

Rigorous scientific review of evidence bearing on a specific clinical question with specific criteria and procedures set in advance.

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8
Q

what are some advantages of a systematic review?

A

Useful for single, focused questions; finds all quality studies; increases power; improves generalizability
(we can take small studies combine them and therefore we can have more statistical power, allows a better picture of whats going on)

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9
Q

what are some disadvantages of a systematic review?

A

expensive and laborious and time consuming

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10
Q

What are the steps in doing a systematic review?

A
  1. Define question
  2. Find relevant studies
  3. select strongest studies
  4. determine scientific strength and quality
  5. summarize in tables and forest plots
  6. determine if pooling (meta analysis) is okay
  7. calculate summary effect size
  8. identify if heterogeneity is present
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11
Q

Does systematic reviews involve published or non published works?

A

both :)

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12
Q

In regards to defining a question, what does the acronym PICO mean?

A
P= patients 
I= Intervention 
C= Comparison 
O= outcomes 
T= time
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13
Q

What are the types of studies for a systematic review?

A

Randomized trials
Cohort
Case Control
Diagnostic Tests

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14
Q

What are some examples of types of systematic reviews that are experimental studies?

A
  1. antiplatetlet drugs for cardiovascular prevention

2. Chrondoitan vs. Placebo for relief of pain from osteoarthritis

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15
Q

What are some examples of types of systematic reviews of observational and diagnostic studies?

A
  1. Smoking as as risk factor for breast cancer
  2. Leg raising test to detect lumbar disk herniation in patients with low back pain and leg pain
  3. Anti-TB IgG test for diagnosis of pulmonary pneumonia
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16
Q

What are some potential biases for publication?

A
Why studies are not reported?
 * Non-significant findings
 * Unpublished data
 * disagreement with findings
Is there a remedy?
 * Cochran collaborators track down leads for systematic reviews 
 * Encourage publication of all results 
 * Registration of all clinical trials
17
Q

One of your patients is an active 73 y.o with constant A-Fib and a history of hypertension. His meds are: aspirin; digoxin; hydrochlorothiazide, enalapril. You wonder whether you should change from aspirin to warfarin to prevent strokes and other clotting problems. What is an appropriate PICO question?

A

P= patient (Elderly with A-fib)
I= intervention (warfarin)
C= comparison ( aspirin or placebo)
O= outcomes (strokes or clotting problems)
Ex. In elderly persons with A-fib does warfarin perform better then placebo to prevent strokes and clotting problems

18
Q

A systematic review finds how many studies that meet stringent criteria?

A

Five (in this case comparing warfarin with aspirin)

19
Q

In regards to epi studies, for a 95% CI, if there is a 1 in the CI, what does this mean?

A

If one in the confidence interval this means that the study is not significant
(aka the null is in the value)

20
Q

What is a meta-analysis?

A

Use of statistical methods to combine results of individual studies, usually from systematic reviews

21
Q

What are the advantages of a meta analysis?

A

can provide an adequate sample size and power to evaluate small treatment effects; especially good if the analysis can be done with the data from individual patients

22
Q

What are the disadvantages of a meta analysis?

A

Quality is dependent on studies, may be too heterogeneous to combine; patients are variable

23
Q

What is a fixed meta analysis?

A

Assumes each study answers the same questions, and has same effect size, so results differ only by chance.

24
Q

What is a random effect model?

A

Assumes studies address different but related questions, a random sample of all studies on that question; takes heterogeneity into account, less likely to overestimate precision, so wide CI considered more realistic.

25
Q

How would you organize data for a review?

A

Odds ratio

26
Q

In regards to a Forest Plot, they show individual study results. How can you determine if the individual study is significant??

A

To the left of the line (less then 1) this indicates there is a difference or significance

27
Q

In regards to the meta analysis, this shows the combined results of the individual studies.

A

If to the left of the middle line (less then 1) this indicates there is a difference or significance of studies combined. (note the two sides of the diamond of the meta analysis indicate the upper and lower ends of the CI)

28
Q

What are some common analyses used in EBM literature and practice?

A

Meta-analysis
Decision analysis
Cost-effectiveness Analysis
Outcome Analysis (aka prognosis)

29
Q

What are Ad hoc or Post hoc analyses?

A

Analyses and outcomes must be specified before the study is conducted

30
Q

What are subgroup analyses?

A

Analyses and out comes must be specified before the study is conducted

31
Q

Is it okay to keep on testing one subgroup against another forever until one is significant?

A

NO
(called multiple comparisons)
(eventually you will find something but this will probably be an error, so you need to fix your alpha)

32
Q

What is evidence based medicine based on?

A

Patient’s concerns, values , expectations
Clinical expertise of the physician
Best available clinically relevant research

33
Q

What are the requirements for EBM (Evidence based medicine)?

A

Life-long learning originating in patient problems

Good information retrieval skills by physicians

34
Q

Evidence-Based Medicine generates constraints on practice, give an example

A

Practice guidelines: ages children should be vaccinated or adults who should get a flu vaccination
Hospital guidelines: certain surgical hardware that you have to use.
Medicare: everyone needs a flu shot because it is cost effective (more expensive to pay for actual flu then vaccination)

35
Q

What are preferred-drug lists?

A

A hospital or a health maintenance organization may decide to adopt a standard list of drugs which they have reviewed and found to be effective in their community, safe and reasonable period.

36
Q

What is the advantage of preferred-drug lists?

A

Their doctors become familiar with this list and are less often surprised by bad side effects, are not visited by drug reps, and the patients save money.

37
Q

A graphical summary known as a forest plot? Can you be confident that all trials studied the exact same research question?

A

Of course not

38
Q

Meta- analysis is done in a systematic review. A graphic summary is shown as a Forest plot. Is the following statement true or false? The summary effect size is the best available estimate of the true effect size for similar patients?

A

true

39
Q

C.C. is a healthy 43y/o office worker. She presents with upper respiratory tract symptoms, which have been getting worse over the past few days. The symptoms she describes are suggestive of sinusitis. Should you order radiographs to make the diagnosis? Which of the following is a well built clinical question using a PICO model?

A

In healthy adults with URI symptoms, does an x-ray compared to watchful waiting better diagnose sinusitis?