Number Needed to Treat

End Points Baseline Risk is the risk associated with a particular condition Baseline Risk is the risk associated with a particular condition Absolute Risk Reduction is the risk difference between the control group and the experimental group Absolute Risk Reduction is the risk difference between the control group and the experimental group

End Points Number Needed to Treat (NNT) is the number of patients who must receive an intervention of therapy during a specific period of time to prevent one adverse outcome or produce one positive outcome Number Needed to Treat (NNT) is the number of patients who must receive an intervention of therapy during a specific period of time to prevent one adverse outcome or produce one positive outcome NNT is inversely related to the absolute risk reduction NNT is inversely related to the absolute risk reduction NNT incorporates the influence of the baseline risk NNT incorporates the influence of the baseline risk Can be expressed in whole numbers Can be expressed in whole numbers

Baseline Risk The absolute risk associated with a particular condition The absolute risk associated with a particular condition Killip Class Mortality in 30 days Killip Class Mortality in 30 days Class I 6% Class II 17% Class III 38% Class IV 81%

Risk After Treatment New risk after receiving experimental treatment New risk after receiving experimental treatment Lytics (experimental treatment) reduces risk by 12% Lytics (experimental treatment) reduces risk by 12% 81%X.12 = %-10%= 71%

Absolute Risk Reduction Risk Difference between your control group and your experimental group Risk Difference between your control group and your experimental group Baseline Risk - Risk after Treatment = ARR or risk difference 81%-71% = 10%

Tale of Two Heart Attacks Patient A Patient A September M with no PMH presents to ED in rural Robeson County with ECG findings suggesting inferior myocardial infarction. No signs of heart failure and is in NSR pulse 90. September M with no PMH presents to ED in rural Robeson County with ECG findings suggesting inferior myocardial infarction. No signs of heart failure and is in NSR pulse 90. Patient B Patient B September M with no PMH presents to ED in rural Robeson County with ECG findings suggesting anterior myocardial infarction with evidence of pulmonary edema

What do you do? A. Go straight to cath lab A. Go straight to cath lab B. Give lytics B. Give lytics C. Heparin and CCU C. Heparin and CCU D. floor with telemetry D. floor with telemetry

Review Patient A Patient A Killip Class I- no signs of heart failure 6% mortality in 30 days Patient B Patient B Killip Class III- frank pulmonary edema 38% mortality in 30 days tPA tPA reduces mortality risk by 12% Killip T, Kimball JT. Treatment of myocardial infarction in a coronary care unit: a two year experience of 250 patients. Am J Cardiol 1967; 20: Treatment of myocardial infarction in a coronary care unit: a two year experience of 250 patients.

Handout Exercise

End Point #1 Number Needed to Treat (NNT) is the number of patients who must receive an intervention of therapy during a specific period of time to prevent one adverse outcome or produce one positive outcome Number Needed to Treat (NNT) is the number of patients who must receive an intervention of therapy during a specific period of time to prevent one adverse outcome or produce one positive outcome

Killip Class I Killip Class I For all Killip Class I pts we would treat 100 pts with lytics to prevent 1 death in 30 days Killip Class II Killip Class II For all Killip Class II pts we would treat 50 pts with lytics to prevent 1 death in 30 days Killip Class III Killip Class III For all Killip Class III pts we would treat 20 pts with lytics to prevent 1 death in 30 days Killips Class IV Killips Class IV For all patient B’s presenting to this hospital we would have to treat 10 pts with lytics to prevent 1 death in 30 days NNT

End Point #2 NNT is inversely related to the absolute risk reduction NNT is inversely related to the absolute risk reduction 100/ARR or Risk Difference = NNT Control tPa Control tPa Patient B 38%33% ARR= 38%-33%= 5% NNT= 100%/5%= 20

End Point #3 NNT incorporates the influence of the baseline risk NNT incorporates the influence of the baseline risk Baseline Risks NNT Patient A 6% (I)100 17% (II) 50 17% (II) 50 Patient B38% (III)20 81% (IV)10 The higher the baseline risk, the higher the ARR, the lower the NNT.