Critiquing for Evidence-based Practice: Therapy or Prevention

1
Critiquing for Evidence-based Practice Therapy
or Prevention

• M8120
• Columbia University
• Suzanne Bakken, RN, DNSc

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Critical Analysis of Therapy or Prevention Studies

• Are the results of the study valid?
• What are the results?
• Will the results help me in caring for my
  patients?

3
Critical Analysis of Therapy or Prevention Studies

• Are the results of the study valid?
• Was the assignment of patients to treatment
  randomized?

4
Critical Analysis of Therapy or Prevention Studies

• Are the results of the study valid?
• Were all patients who entered the trial properly
  accounted for and attributed at its conclusion?
• Follow-up complete
• Intent to treat analysis

5
Critical Analysis of Therapy or Prevention Studies

• Are the results of the study valid?
• Were patients, their clinicians, study personnel
  blind to treatment?

6
Critical Analysis of Therapy or Prevention Studies

• Are the results of the study valid?
• Were the groups similar at the start of the trial?

7
Critical Analysis of Therapy or Prevention Studies

• Are the results of the study valid?
• Aside from the experimental intervention, were
  the groups treated equally?

8
Critical Analysis of Therapy or Prevention Studies

• Are the results of the study valid?
• What are the results?
• Will the results help me in caring for my
  patients?

9
Critical Analysis of Therapy or Prevention Studies

• What are the results?
• Focus on clinical rather than statistical
  significance?
• How large was the treatment effect?
• How precise was the estimate of the treatment
  effect?
• RR, RRR, CI, etc.

10
Critical Analysis of Therapy or Prevention Studies

• Risk without therapy (Baseline) X
• Risk with therapy Y
• Absolute Risk Reduction(ARR) (risk difference)
  X - Y
• Relative risk (RR) Y/X
• Relative risk reduction (RRR)X-Y (ARR)/X
  (baseline) 100
• Confidence interval (CI) range that includes
  the true RRR a set percentage of time

11
Critical Analysis of Therapy or Prevention Studies

• Death 20 in control group and 15 in
  experimental
• How large was the treatment effect?
• Risk without therapy (Baseline) X
• Risk with therapy Y
• Absolute Risk Reduction(ARR) (risk difference)
  X - Y
• Relative risk (RR) Y/X
• Relative risk reduction (RRR)X-Y (ARR)/X
  (baseline) 100

12
Critical Analysis of Therapy or Prevention Studies

• Target disorder Type I diabetes
• Rx intensive insulin treatment
• Event prevented (Diabetic retinopathy) 9.6 in
  control group and 2.8 in experimental
• How large was the treatment effect?
• Risk without therapy (Baseline) X
• Risk with therapy Y
• Absolute Risk Reduction(ARR) (risk difference)
  X - Y
• Relative risk reduction (RRR)X-Y (ARR)/X

13
Critical Analysis of Therapy or Prevention Studies

• Target disorder Type I diabetes
• Rx intensive insulin treatment
• Event prevented (Diabetic retinopathy) 9.6 in
  control group and 2.8 in experimental
• How large was the treatment effect?
• Risk without therapy (Baseline) X.096
• Risk with therapy Y. 028
• Absolute Risk Reduction(ARR) (risk difference)
  X Y .068
• Relative risk reduction (RRR)X-Y (ARR)/X .71

14
Critical Analysis of Therapy or Prevention Studies

• Target disorder independent elderly
• Rx Comprehensive geriatric assessment
• Event prevented (long term nursing home
  admission) 10 in control group and 4 in
  experimental
• How large was the treatment effect?
• Risk without therapy (Baseline) X
• Risk with therapy Y
• Absolute Risk Reduction(ARR) (risk difference)
  X - Y
• Relative risk reduction (RRR)X-Y (ARR)/X

15
Critical Analysis of Therapy or Prevention Studies

• Are the results of the study valid?
• What are the results?
• Will the results help me in caring for my
  patients?

16
Critical Analysis of Therapy or Prevention Studies

• Will the results help me in caring for my
  patients?
• Are the results applicable to my patient?
• Were all clinically important outcomes
  considered?
• Are the likely treatment benefits worth the
  potential harm and costs?

17
Critical Analysis of Therapy or Prevention Studies

• Will the results help me in caring for my
  patients?
• Are the results applicable to my patient?

18
Critical Analysis of Therapy or Prevention Studies

• Will the results help me in caring for my
  patients?
• Were all clinically important outcomes considered?

19
Critical Analysis of Therapy or Prevention Studies

• Will the results help me in caring for my
  patients?
• Are the likely treatment benefits worth the
  potential harm and costs (number needed to treat)?

20
Critical Analysis of Therapy or Prevention Studies

• Number needed to treat
• 1/ARR
• Benefits AND risks (including costs) of treatment
  depend on
• RRR
• Risk of adverse outcome it is designed to prevent
  (i.e., prior probability)

21
Critical Analysis of Therapy or Prevention Studies

• Ezekowitz et al, 1992 - Warfarin Rx with
  nonvalvular atrial fibrillation
• Baseline risk of stroke 0.043
• Risk of stroke with Rx 0.009
• ARR 0.043-0.009 0.034
• NNT to prevent 1 stroke 1/0.034 30

22
Critical Analysis of Therapy or Prevention Studies

• Importance of baseline risk (prior probability) -
  Example beta blocker after MI
• Baseline risk 0.01 vs. 0.10
• RR with therapy 0.75
• ARR ? And ?
• NNT ? And ?

23
Critical Analysis of Therapy or Prevention Studies

• Diastolic BP 115-129
• Baseline risk of death, stroke or MI 13
• Risk of death, stroke or MI with Rx 1.4
• NNT

24
Critical Analysis of Therapy or Prevention Studies

• Diastolic BP 90-109
• Baseline risk of death, stroke or MI 5.5
• Risk of death, stroke or MI with Rx 4.7
• NNT