2. Objectives
Understand RR ARR and NNT.
Learn how to convert one to the other.
Understand why natural frequencies are
so much more helpful to physicians.
3. RR ARR NNT
What’s the difference between
Relative Risk
Absolute risk reduction
Number needed to treat
4. Work something out
10% of AMI patients are dead at one
month.
A new treatment reduces the mortality to
5%
Work out the RR, ARR and NNT
5. Work something out
10% of AMI patients are dead at one month.
A new treatment reduces the mortality to 5%
Work out the RR, ARR and NNT
RR - 5/10 = 50% reduction
ARR - 10-5 = 5% reduction
NNT - ARR/100 = 20 patients treated to achieve one
positive result.
6. Work something out again
20% of AMI patients are dead at one
month.
A new treatment reduces the mortality to
10%
Work out the RR, ARR and NNT
7. Work something out again
20% of AMI patients are dead at one month.
A new treatment reduces the mortality to 10%
Work out the RR, ARR and NNT
RR - 10/20 = 0.5 = 50% reduction
ARR - 20-10 - 10% reduction
NNT - 10/100 = 10 patients to achieve one positive
result
8. RR, ARR, NNT
How much better is it to do
an internal jugular line with
ultrasound as compared to
an internal jugular line with
landmark method?
