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Evidence Based Medicine > Exam 1: Hoff > Flashcards

Exam 1: Hoff Flashcards

1
Q

Modern Definition of EBM

A

USe of mathematical estimates of risk of benefit and harm, deried from high-quality research on population samples, to inform clinical decision-making in the diagnosis, investigation, or management of individual patients

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2
Q

EBM emphasizes… (4 things)

A

Best Evidence

Clinical Expertise

Patient Values

Patient Circumstances

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3
Q

Best Evidence

A

Valid and Clinically Relevant

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4
Q

Clinical Expertise

A

Clinical skills/experience to understand patient’s situation, diagnosis, risks, and possible benefits from interventions

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5
Q

Patient Values

A

Preferences, concerns and fears, expectations

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6
Q

Patient Circumstances

A

Individual status and clinical setting

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7
Q

What are the 5 basic steps in EBM?

A
  1. Ask answerable questions
  2. Search for best evidence
  3. Critical appraisal for validity and relevance
  4. Integrate evidence, clinical expetise, and patient values/preferences and apply
  5. Evaluate results
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8
Q

Clinicians Incorporate Evidence by: Doing Mode (Define)

A

Carry out at least the first 4 steps (Ask AQ, Best Ev, Appraisal, Integrate/Apply, Evaluate)

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9
Q

Using Mode (Define)

A

Restricts searches to sources have already been critically appraised (only step 1 and 2)

***Generally for uncommonly seen problems***

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10
Q

Replicating Mode

A

Following the opinions of recognized experts regarding very rare entities

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11
Q

What does PICO stand for?

A

Patient or Problem

Intervention

Comparison Intervention

Outcomes

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12
Q

Background Questions

A

Seek General Knowledge (Students)

Two Components:

  • Who, what, where, when, why, how?
  • Plus the disorder itself
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13
Q

Foregroud Questions (Majority)

A

***Clinicians***

Seek specific knowledge for patient management

-Comprise three or four elements (PICO)

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14
Q

What source is the best when searching for evidence?

A

Electronic (online) sources

-More likely to be current, updated, and (now in many cases) evidence-based

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15
Q

What constitutes best evidence?

A

Current, valid, and clinically relevant

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16
Q

Hierarchy of study reliability:

A

Systematic reviews (or meta-analyses) of RCTs

Randomized, controlled trials (RCTs)

Prospective Studies

Retrospective Studies

Cross-sectional Surveys

Case Series

Case Reports

***SRPRCCC***

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17
Q

What is the best site for systematic reviews?

A

The Cochrane Collaboration

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18
Q

What type of study design is not randomized?

A

Case-control studies

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19
Q

Which type of study will bring bias, as certain things are being looked for?

A

Cross-sectional surveys

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20
Q

What is IMRAD and what is it used for?

A

Abstract

Introduction (why the research was done)

Methods (how the research was structured)

Results (what was found)

How Analyzed

Discussion (what the researchers think the results mean)

IMRAD is the standard structure of research papers

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21
Q

What 3 preliminary questions should be asked?

A
  1. Why was the study in question done; what hypothesis was tested?
  2. What type of study was done? (e.g. primary or secondary)
  3. Was the study design appropriate to the broad topic of research addressed?
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22
Q

What are examples of primary studies? Secondary studies?

A

Primary: Experiments, Observations, Clinical Trials (Therapies, Diagnostics, etc.), Surveys, Questionnaires

Secondary: Reviews (systematic or non-systematic), Economic analyses, Decision analyses

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23
Q

Intervention (Therapy)

  1. Best Study Design
  2. Description
A
  1. RCT
  2. Subjects randomly allocated to treatment or control and outcomes assessed
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24
Q

Harm/Risk/Etiology

  1. RCT
  2. Description
A
  1. RCT
  2. Similar to intervention questions, but RCTs to assess harmful outcomes are not ethical
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25
Q

Harm/Risk/Etiology

  1. Cohort Study
  2. Description
A

Outcome(s) compared for matched groups with and without exposure or risk factor (prospective)

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26
Q

Harm/Risk/Etiology

  1. Case-Control Study
  2. Description
A

Subjects with and without outcome of interest are compared for previous exposure (retrospective)

***more bias, but occasionally done to look at harm or risk***

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27
Q

Diagnosis

  1. Best Study Design
  2. Description
A
  1. Diagnostic Validation Study
  2. Independent, blinded comparison with reference (“gold”) standard
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28
Q

Prognosis/Prediction

  1. Best Study Design
  2. Description
A
  1. Cohort Study
  2. Long-term followup of representative cohort to determine outcome
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29
Q

Randomized Control Trials

  1. Concealed allocation
A
  1. Randomization generally should be concealed
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30
Q

Randomized Controlled Trials

  1. Single- vs. Double-Blind
A

Single (only subjects)

Double (subjects and investigators)

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31
Q

RCTs

  1. Advantages
A

Allow rigorous evaluation of a single variable

Designed prospectively

Seek to confirm a null hypothesis

Allow for meta-analysis

Minimize bias

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32
Q

RCTs

  1. Disadvantages
A

Expensive

Require long-term study (months to years)

Could introduce hidden bias

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33
Q

When is randomization inappropriate?

A

When the study involves prognosis of a disease

Investigating the validity of a diagnostic or screening test

Investigating quality of care issues when criteria for success are not known yet

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34
Q

Cohort Studies

  1. Design
  2. Prognosis Studies
  3. Bias
A
  1. Observational - NO intervention
    - Two or more subject groups selected based on exposure or no exposure to a particular substance/organism to compare outcome
  2. Prognosis Studies: special case - usually intended to determine what happens to people with a certain diagnosis or problem (e.g. heart failure) over time
    - Require long-term follow up
  3. Can be substantially bias
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35
Q

Case-Control Studies

  1. Design
  2. Bias
  3. Concerned with
A
  1. Observational, not randomized
    - Patients with certain condition, “matched” with controls data usually obtained retrospectively for exposure to a disease-causing agent or circumstance
  2. More prone to bias than cohort studies
  3. Generally concerned with harm or etiology
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36
Q

Cross-Sectional Surveys

  1. Design
  2. Bias
  3. Other uses
A
  1. Representative sample interviewed, examined, or evaluated about a specific question
    - Data are collected at a specific time but often include retrospective information
  2. Potential for significant bias
  3. Also used in questions of Etiology
37
Q

Case Reports

  1. Design
A

Simple report of a medical history

  • Sometimes a series of patients’ histories are reviewed and analyzed together
  • Weak statistically but may give occasional insights into rare or unusual conditions

Weakest: report of a single case

38
Q

Systematic Reviews

  1. Design
  2. Key Features
A
  1. Commonly employed in evaluating/comparing RCTs; can be used to compare others as well
    - Conducted according to strict methodology
  2. Key Features:
    - Statement of objectives, materials, and methods
    - Include all original reports available, globally, even if unpublished
    - Individual reports each critically evaluated
    - Conclusions based only on studies meeting pre-set quality criteria
39
Q

Systematic Reviews

  1. Advantages
A
  • Large amounts of information assimilated quickly
  • Explicitly limit bias when selecting studies for review
  • Compare studies for consistency and generalizability
  • Inconsistency (heterogeneity) is easily identified and new hypotheses can be formulated
  • Conclusions are more reliable
  • Quantitative reviews (Meta-Analyses) increase precission of overall results
40
Q

Meta-Analysis

  1. Design
A

A statistical synthesis of numerical results of several studies which all addressed the same question

  • Incorporate the advantages of systematic reviews
  • Powerful statistical analysis
41
Q

Diagnosis Studies

  1. Uses
  2. Randomization
A
  1. Screening a general or specific population, Diagnosis in an individual, Patient follow-up and management
  2. NOT randomized
42
Q

Three Preliminary Questions to ask for all papers:

A
  1. Why was the study done? (purpose or hypothesis? background?)
  2. Primary vs Secondary
  3. Appropriate Design (e.g. RCT, Cohort, Case-Control, etc.)

***Check the abstract first***

43
Q

What should be assessed first when reviewing the results of Diagnosis Studies?

44
Q

Questions to ask when verifying Validity?

A
  1. Research question clearly defined?
  2. Presence or absence of disorder confirmed by reference test (aka the Gold Standard)
    - How did investigators know the disorder was present?
    - Was comparison indepndent and blinded?
  3. Was test evaluated on an appropriate spectrum of patients?
  4. Reference standard applied to all patients?

-

45
Q

Diagnosis Studies: Clinical Important

  1. Questions to Ask
  2. Ideal Test
A

How accurate is the test/What is its sensitivity and specificity?

***Ideal test will produce a high proportion of true positives and true negatives

46
Q

What is the usefulness of any Diagnostic Test based on?

A

Its accuracy in identifying the disorder

47
Q

Diagnostic Studies: Likelihood Ratios

A

Measure of accuracy

Predict likelihood of a certain result in a patient with the target disorder when compared to the likelihood of the same result in someone without it

48
Q

Diagnostic Studies: Sensitivity vs Specificity

A

Sensitivity: proportion with** the disease testing **positive

Specificity: proportion without** the disease testing **negative

49
Q

Diagnostic Studies: SpPin and SnNout

A

SpPin: if test with high specificity is positive, rules the condition IN

SnNout: if test has high sensitivity and is negative, rules the condition OUT

50
Q

Diagnostic Studies

  1. Pre-Test Probability
  2. Post-Test Probability
A
  1. Pre: based on estimates of prevalence (how often a condition is found in a specific population)
  2. Post: a good test increases post-test probability significantly
51
Q

Diagnostic Studies

What does a likelihood ratio (LR) of 1 mean?

LR > 1?

LR < 1?

A

LR = 1 means that post-test and pre-test probability is the same

LR > 1 increases the probability; says the test is accurate and helpful

LR < 1 decreases the probability; says the test is not helpful

***Represented with Bayes’ Theorem***

52
Q

Diagnostic Studies

  1. Will the results change your management?
A

If the LRs are close to 1, then post and pre test probabilities will be similar and therefore not very useful

53
Q

Therapy Studies

  1. Two key questions to ask
A

Do they have a clear question?

Is it randomized?

54
Q

Therapy Studies

  1. About
A

***Most common kind of clinical papers, by far***

  • Ideally performed randomized
  • Studies of adverse reactions to therapy (studies of harm or risk) are done differently
55
Q

Preliminary Questions for all papers

A

Why was the study done?

Primary vs secondary?

Appropriate design?

56
Q

Primary vs Secondary

A

Primary: trying to find new info

Secondary: meta analyses or systematic reviews

57
Q

Therapy Studies

  1. Validity
A

Clearly defined question?

Randomized?

***Blinded***

Concealed Allocation

58
Q

Therapy Studies: Validity

  1. What is the most important thing to look for in RCTs?
A

Concealed Allocation

-Avoids selection bias if clinicians do not assign gropus

59
Q

What is the Rule of Thumb for assessing the Validity of Therapy Studies?

A

If less than 80% completed followup, likely invalid

60
Q

Therapy Studies: Validity

  1. Intention to Treat
A

Preserves randomization (minimizes bias)

-Means all data from subjects in the intervention group is analyzed

61
Q

Therapy Studies: Validity

  1. What happens if researchers fail completely analyze subjects with their assigned group?
A

Results can be skewed toward the intervention

62
Q

Therapy Studies: Importance

  1. Three questions to ask
A

How large is the effect of treatment? (accuracy)

How precise are the findings?

How useful is this in practice?

63
Q

What is another term for systematic error?

64
Q

What does a p-value of < 0.05 mean?

A

It means that there is less than a 1 in 20 probability that the result is due to chance alone

Smaller p-value = less likely due to chance

65
Q

Therapy Studies: Importance

  1. Confidence Intervals
A

Stated in Results section of a paper as a range of values around a demonstrated difference

When the CI crosses 1.0 (“Line of No Difference”) the result of interest is not statistically significant

66
Q

Therapy Studies: Importance

  1. Number Needed to Treat (NNT)
A

On average, if you do this intervention to this set of people who have this set of problems, if you treat x number, you will get a good result

***Number of patients you would have to treat to achieve one good result*** (or avoid one negative)

***Lower NNT = BETTER***

1 is the best, 100% will have an effect

67
Q

Therapy Studies: Importance

  1. What is the most important part of treatment?
A

It is important that treatments improve outcomes that are important to patients

Better Approach: Is there a compelling reason why results should not be applied to your practice?

68
Q

Summary of Therapy Studies

  1. Best Studies of Treatment
  2. Determine Validity (5)
  3. Determine Importance (3)
A
  1. RCTs
  2. Clearly defined research question

Randomization and blinding

Intention to treat

Equal treatments of groups

Comparable groups at the beginning

  1. Accuracy

Precision (p values, ***CIs*** (Best))

Usefulness in your practice

69
Q

Harm/Risk/Etiology Studies

  1. Study Types
  2. Definition
A
  1. Cohort Studies (prospective) or Case-Control Studies (retrospective)
  2. Observational and Collecting Information

***These studies investigates what happens (or happened) as a result of an exposure***

70
Q

Harm/Risk/Etiology: Importance

  1. 3 Questions to Ask
A

How strong is the association between exposure and outcome?

How precise is the estimate of risk?

  • If cohort study (Prospective), must use RR (Relative Risk) i.e. Hazard Ratio (HR)
  • if case-control study (Retrospective), use OR (Odds Ratio)

Statistical Significance?

-Look for 95% CI around results - if RR or OR cross 1.0 then no effect

71
Q

Prognosis Studies

  1. Definitions
  2. Prognostic Factors
A
  1. Possible outcomes of a disease or condition and
    - Frequency with which possible outcomes occur

Synonym is _***natural history***_ of an ailment

  1. Prognostic Factors: characteristics or population that can be used to more accurately predict that patient or population’s outcome
    - Demographic (e.g. age, gender, etc.)
    - Disease-specific (e.g. tumor stage)
    - Comorbidity (e.g. diabetes in a cardiac patient)
72
Q

Which type of study is best for studies of prognosis?

A

Cohort Studies (prospective)

Also can use Case-control studies

73
Q

Prognosis Studies: Importance

  1. Questions to ask
A

What is the risk of the outcome over time?

How preceise are the estimates of risk?

74
Q

Prognosis Studies: Validity

  1. 3 questions to ask
A

Was there a representative and well-defined sample of subjects? (recruied at common point in illness, inclusion/exclusion criteria, representative setting, similar to your own patients)

Was follow up sufficiently long and complete? (>20% lost to followup, validity is suspect)

Were outcomes measured “blind”?

75
Q

Prognosis Studies: Referral Bias

  1. Definition
A

A systematic error that can occur when patients are selected from different care settings (e.g. tertiary care compared to primary care centers) thus increasing the likelihood of adverse or unfavorable outcomes

76
Q

Prognosis Studies

  1. Were objective and unbiased criteria used?
A
  • Outcome of interest is defined before the study starts
  • Criteria for diagnosis of outcome of interest should be as objective as possible
  • Blinding of individual(s) measuring outcome is best but not alwasy possible
77
Q

Prognosis Studies

  1. Reassuring a Concerned Patient/Relative
A

A valid, precise, and generalizable result of good prognosis is usually very helpful in reassuring

78
Q

Systematic Review

  1. Definition
A

Review of a clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research and to collect and analyze data from studies included

  • Research synthesis
  • Research integration
  • Information synthesis
  • Overview
79
Q

Meta-Analysis

  1. Definition
A

Statistical analysis of a collection of analysis results from individual studies for the purpose of integrating the findings

80
Q

Systematic Reviews: Importance

A

Odds Ratios

Relative Risk

81
Q

Systematic Reviews: Validity

  1. High quality studies means…
  2. How and what trials were found?
  3. Are results consistent across studies?
A
  1. RCTs
  2. Should go beyond standard databases, Should include all relevant studies (including worldwide and non-published)
  3. What criteria used to extract data (think PICO)
    - Clinical heterogeneity makes studies less useful
82
Q

Odds Ratio

  1. Used
  2. What does OR of 1 mean?
A
  1. Used in case-control studies to copmare whether or not probability of a certain even tis the same in two groups
  2. The event is equally likely in both groups
83
Q

Relative Risk

  1. Used
  2. What does a RR of 1 mean?
A
  1. Used in RCT (randomized clinical trials)or incohort studies to state risk of an event (or developing a disease) relative to exposure
  2. Means that the treatment did not do anything, as it is equally probable in both groups
84
Q

Systematic Reviews: Integrating the Findings

  1. Single Studies
  2. Studies can disagree with respect to:
A
  1. Single Study rarely provides definitive conclusions; reviewing a group of similar studies adds power
  2. Can disagree with respect to:
    - Clinical Significance: the magnitude of effect
    - Statistical Significance: the likelihood that an observed effect occurred by chance alone
85
Q

What does the PICO mnemonic help with?

A

Asking Answerable Questions

86
Q

What does PICO stand for?

A

Patient or population

Intervention

Comparison intervention

Outcome of interest

87
Q

What is the basis for evidence based medicine?

A

Asking truly answerable questions

88
Q

What is the best design for a study of Therapy?

A

Double blind, randomized control trial

89
Q

Studies on prognosis seek information on which of the following?

  1. The reason a particular condition has happened
  2. The results of a particular intervention
  3. The outcome of a test for a condition
  4. The possible outcomes of a disease or condition
  5. Which patients survive longest
A

The possible outcomes of a disease or condition

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