Critiquing for Evidence-based Practice: Therapy or Prevention

1. Critiquing for Evidence-based Practice: Therapy or Prevention M8120 Columbia University Suzanne Bakken, RN, DNSc

2. 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=