Evidence based practice
From:- Wai-Ching Leung wp102@yahoo.com
Therapy - calculating ARR and NNT adjusted for a specific patient
A randomised controlled trial may give useful information on the relative effectiveness of two or more treatments. However, since the baseline risk of the subjects in the study may differ from our patients, we must NOT directly apply the values of absolute risk reduction (ARR) and numbers needed to treat (NNT) from the study. So, we need to calculate these values specifically adjusted for the baseline risk of our patients.
Fortunately, we can adjust these values for specific patients if we know their baseline risk for our patient (i.e. patient expected event rate, PEER).


Enter the experimental event rate (EER) from the study as a decimal (between 0 and 1):
Enter the control event rate (CER) from the study as a decimal (between 0 and 1):
Enter your patient expected event rate (PEER) as a decimal (between 0 and 1):
Absolute risk reduction (ARR) for your patient:
Number needed to treat (NNT) for your patient


This page is created and maintained by Wai-Ching Leung
e-mail:- wp102@yahoo.com
last modified 17 September 2001