RCT- Dr.Z

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33 Terms

1
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FYI on what to focus on for each section for Dr. Z:

  • green section- characteristics of RCTs

  • 2 Exam Q

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2
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FYI on what to focus on for each section for Dr. Z:

  • blue section- internal v external validity

  • 2 Exam Q

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3
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FYI on what to focus on for each section for Dr. Z:

  • purple section- randomization, blinding, and sample size

  • 2 Exam Q

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4
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FYI on what to focus on for each section for Dr. Z:

  • orange section- different equations dealing w/ risk

  • 2 Exam Q

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5
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FYI on what to focus on for each section for Dr. Z:

  • pink section- 3 strengths and weaknesses of RCTs

  • 1 Exam Q

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6
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What are the 10 characteristics of RCTs?

  • 2 EXAM Q from this LIST!!!!

  1. Primary study

  2. Near Perfect Conditions

  3. Level 1 Evidence

  4. Experimental

  5. Strongest type of study design

  6. strong internal validity

  7. Prospective

  8. Unfiltered

  9. Best Research

  10. GOLD STANDARD

7
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A characteristic of RCT is strong internal validity. If a RCT has strong internal validity, it indicates what? Additionally, to minimize threats to Internal validity, what can we do?

Strong Internal Validity= Causal Relationship

To minimize threats: control group, randomization, blinding, etc.

8
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What is bias and how is it minimized?

bias- systematic error in study design or implementation that can lead to incorrect findings


to minimize- use the right study design and implement it

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What’s validity and the 4 subtypes of validity?

Validity- degree to which findings represent TRUTH (I think we know what the word valid means)


  1. face (are they testing what they say they are going to test)

  2. content- (is it correct to experts?)

  3. criterion- (Does it match up w/ a gold standard)

  4. construct- (Does it relate to theoretical concepts)

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What is internal validity? How is internal validity strengthened?

Internal Validity- Degree to which the study outcome (efficacy or safety) can be explained by the differences in the intervention (treatment)


Strengthened: by having a control group and randomization

11
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List and briefly describe the 8 key biases that threaten internal validity?

  1. selection Bias- putting pts. in specific groups

  2. history Bias- study outcome may be bc of External events

  3. maturation Bias- normal change in pts. over time

  4. Attribution Bias/ Mortality- “Drop-Out” (pt. leaves)

  5. Testing Bias- pts. taking tests repeatedly

  6. Instrumentation Bias- sensitivity of instrument, improved technology, changes in measurement

  7. Investigator Bias- error by investigator

  8. Detection/Surveillance Bias- difference btwn groups in how outcomes are determined

12
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Which of the 8 key biases can be minimized by randomization?

  • selection bias

  • maturation bias

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Which of the 8 key biases can be minimized by control group?

  • history bias

  • maturation bias

  • testing bias

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Which of the 8 key biases can minimized by blinding?

  • investigator

  • detection/surveillance bias

15
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What is external validity and what criteria does it relate to?

indicates that the findings of a given study can be generalized to other settings


inclusion and exclusion criteria

16
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What 5 key factors that threaten external validity?

  1. subject selection

  2. treatment of patients

  3. study location/setting

    • HAWTHORNE EFFECT

  4. historical factors

  5. multiple treatments

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What is the Hawthorne Effect?

study subjects modify their behaviors due to longitudinal learning over the course of a study or because they know they are being observed

  • basically: subjects act different because they know ppl are watching them

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What is randomization and what are the 3 methods of randomization?

process of assigning pts. to a treatment or control group based on chance alone


  1. simple- random # generator

  2. stratified- by characteristics

  3. block- divided into blocks before, then blocks randomized

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List and describe the 4 types of blinding:

  1. single blind- pt/investigator unaware

  2. double blind- both pt/investigator unaware

  3. triple blind- everyone unaware (pts, investigator, data collectors)

  4. open label- everyone IS AWARE

20
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Sample size is the number of subjects that are needed to test the primary hypothesis… WHAT 2 KEY FACTORS does it take into consideration.

  • PLEASE KNOW THIS

  1. EFFECT SIZE

  2. POWER

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What are the 3 most common types of control groups and when are they used?

  1. placebo control- when no known effective therapy

  2. active control- when KNOWN effective therapy

  3. historical (external) control- pts. compared to an old control group

22
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Describe each of the following RCT designs:

  1. parallel

  2. crossover

  3. superiority

  4. noninferiority

  1. parallel- each subject either tx or control group

    • ex: drug A or placebo

  2. crossover- each subject receives all txs

    • ex: drug A and drug B

  3. superiority- one better than the other

  4. noninferiority- sees whether two interventions are equivalent

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2 disadvantages of crossover RCT design:

  1. carryover effect

  2. washout period

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What is intention-to-treat analysis?

  • analyzes patients AS IF THEY COMPLETED the study in their originally assigned group

  • preferred in superiority trials

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Describe on-treatment (per-protocol) analysis:

  • we can see the true effect of study drug

  • preferred in noninferiority trials

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What is risk and how do we calculate it?

probability of an event when an intervention is given


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What is relative risk and how do we calculate it?

  • difference between groups in PROSPECTIVE STUDIES

  • RR < 1 means lower risk/negative association


    RR= risk in tx group/ risk in control group

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What is relative risk reduction and how do we calculate it?

how much the risk is reduced in the treatment group compared to the control group


RRR- 1- RR

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What is absolute risk reduction and how do we calculate it?

  • true difference in risk

  • increase utility


ARR= (risk in control group) - (risk in treatment group)

30
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What is the “number needed to treat” and how do we calculate it?

  • effectiveness of intervention

  • want a LOW number

  • always ROUND UP


NNT= 1/ ARR

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What is the “number needed to harm” and how do we calculate it?

  • risk to pt. from an intervention

  • ROUND DOWN


NNH= 1/ ARR

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What are the 3 strengths of RCTs?

  1. can determine UNBIASED EFFICACY of an intervention

  2. PROSPECTIVE DESIGN allows for control

  3. Methods and protocols allow ability to IDENTIFY CAUSAL RELATIONSHIPS

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What are the 3 weaknesses of RCTs?

  1. limitations on generalizability

  2. potential HAWTHORNE EFFECT

  3. takes lots of time/expensive