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EBP > Evaluating the evidence for an intervention > Flashcards

Evaluating the evidence for an intervention Flashcards

1
Q

What are the 5 As?

A 
Asking - question
Accessing - search
Appraising - critical evaluation
Applying - extracting
Assessing (re) - evaluate process
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2
Q

Essential components to a background question (2)

A
  1. Question root and a verb, e.g. who

2. Disorder, test, Rx etc

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3
Q

Essential components to a foreground question (2)

A

PICO

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4
Q

What is the best type of randomisation?

A

Off-site, computerised system

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5
Q

What does the standard deviation measure?

A

Measure of the distribution of values within a sample.

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6
Q

To correct for not having the full population for SD?

A

Sample - 1

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7
Q

What does the standard error measure?

A

Amount of variability in the sample mean.

It defines the limits of the distribution of sample means.

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8
Q

95% Confidence Interval = in SE?

A

~2SE

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9
Q

Hypothesis tests (aim, issues)

A

HTs determine if relationships are real or related to chance.

Problems

  • no clinical importance shown
  • may get type 2 errors
  • p value is not a direct indicator of effect size
  • size of the true effect is unknown
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10
Q

What is WMD?

A

Weighted mean difference

- different outcomes weighted based on sample sizes and differing precision.

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11
Q

Why use CIs? (3)

A
  • Accuracy of sample statistic
  • Helpful with clinical importance
  • Function as a hypothesis test
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12
Q

How does sample size affect precision?

A

Higher precision with greater sample size.

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13
Q

Magnitude of treatment effect?

A

Difference between values

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14
Q

Precision of estimated treatment effect?

A

CIs

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15
Q

What are the three common measures of risk?

A

Absolute Risk Reduction (ARR)
Relative Risk Reduction (RRR)
Number Needed to Treat (NNT)

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16
Q

What is the CER and EER?

Briefly describe.

A

Control Event Rate
Experimental Event Rate

i.e. control group no. with event occurring/total control group, e.g. 26/32; 81.25%

17
Q

What is ARR and how is it calculated?

A

Difference in risk between Rx and control groups.

ARR = CER - EER

18
Q

What does a negative ARR indicate?

A

Greater risk in the Rx group (good if the event is positive)

19
Q

How are CIs calculated for ARR?

A

95% CI ~= diff in risk +/- 1/sqrt(average ‘n’ of the two groups)

20
Q

What is the NNT? (3)

A

The number of people you would need to treat (on average) to prevent the even of interest happening to one person.

i.e. a lower NNT is a more effective Rx

NNT should be related to a time period of Rx

21
Q

How is the NNT calculated?

A

1/ARR

22
Q

What is the RR?

A

Relative Risk.

  • a measure estimating the size of the effect of a Rx vs another Rx/control.
  • proportion of bad outcomes in the Rx/bad outcomes in the control group
  • EER/CER
23
Q

How are the results of RR interpreted?

A

Below 1 is good
1 is no difference
Above 1 is bad (more risk with Rx)

24
Q

What does the RRR tell us and how is it calculated?

A

How much the Rx reduced the risk of bad outcomes relative the control group.

RRR = ARR/CER

25
Q

Why should you be cautious of RRR? (example)

A

e.g. CER = 5.7% and EER = 4.4%; or CER = 0.000057 and EER = 0.000044

Both = 25% RRR

But much lower ARR in second one and way higher NNT.

26
Q

How is an odds ratio calculated?

A

EER/(1-EER) / CER/(1-CER)

27
Q

Is the evidence applicable to your patient?

A
  1. Subjects similar? (inc/exc criteria, prognostic indicators)
  2. Rx applied appropriately, and can I perform them?
  3. Are the outcomes useful?
  4. Does the therapy do more good than harm/are there side effects?
28
Q

What does “Are the outcomes useful?” refer to? (3)

A
  • surrogate measures aren’t usually, e.g. BMD for # risk
  • outcome important to pt
  • size of the effect clin sig?
29
Q

What is an odds ratio? (2)

A

Odds that an outcome will occur given a particular exposure

COMPARED to odds of the outcome occurring without the exposure.

EBP (8 decks)

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