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

2. Critical Analysis of Therapy or Prevention Studies 4Are the results of the study valid? zWhat are the results? zWill the results help me in caring for my patients?

3. Critical Analysis of Therapy or Prevention Studies zAre the results of the study valid? –Was the assignment of patients to treatment randomized?

4. Critical Analysis of Therapy or Prevention Studies zAre 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 zAre the results of the study valid? –Were patients, their clinicians, study personnel “blind” to treatment?

6. Critical Analysis of Therapy or Prevention Studies zAre the results of the study valid? –Were the groups similar at the start of the trial?

7. Critical Analysis of Therapy or Prevention Studies zAre the results of the study valid? –Aside from the experimental intervention, were the groups treated equally?

8. Critical Analysis of Therapy or Prevention Studies zAre the results of the study valid? 4What are the results? zWill the results help me in caring for my patients?

9. Critical Analysis of Therapy or Prevention Studies zWhat are the results? zFocus 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 zRisk without therapy (Baseline)= X zRisk with therapy = Y zAbsolute Risk Reduction(ARR) (risk difference) = X - Y zRelative risk (RR) = Y/X zRelative risk reduction (RRR)=X-Y (ARR)/X (baseline) * 100 zConfidence interval (CI) = range that includes the true RRR a set percentage of time

11. Critical Analysis of Therapy or Prevention Studies zDeath = 20% in control group and 15% in experimental zHow 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 zTarget disorder – Type I diabetes zRx – intensive insulin treatment zEvent prevented (Diabetic retinopathy) = 9.6% in control group and 2.8% in experimental zHow 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 zTarget disorder – Type I diabetes zRx – intensive insulin treatment zEvent prevented (Diabetic retinopathy) = 9.6% in control group and 2.8% in experimental zHow 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 zTarget disorder – independent elderly zRx – Comprehensive geriatric assessment zEvent prevented (long term nursing home admission) = 10% in control group and 4% in experimental zHow 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 zAre the results of the study valid? zWhat are the results? 4Will the results help me in caring for my patients?

16. Critical Analysis of Therapy or Prevention Studies zWill 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 zWill the results help me in caring for my patients? –Are the results applicable to my patient?

18. Critical Analysis of Therapy or Prevention Studies zWill the results help me in caring for my patients? –Were all clinically important outcomes considered?

19. Critical Analysis of Therapy or Prevention Studies zWill 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 zNumber 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 zEzekowitz 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 zImportance 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 zDiastolic 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 zDiastolic BP 90-109 –Baseline risk of death, stroke or MI = 5.5% –Risk of death, stroke or MI with Rx = 4.7% –NNT=