Definition
The NNT is the number of patients who need to be treated in order to prevent one additional bad outcome. It is the inverse of the Absolute Risk Reduction (ARR).
CER = control group event rate
EER = experimental group event rate
Sample Calculation
The results of the Diabetes Control and Complications Trial* into the effect of intensive diabetes therapy on the development and progression of neuropathy indicated that neuropathy occurred in 9.6% of patients randomised to usual care and 2.8% of patients randomised to intensive therapy. The number of patients we need to treat with the intensive diabetes therapy to prevent one additional occurrence of neuropathy can be determined by calculating the absolute risk reduction as follows:
Practice Calculation
In a randomised controlled trial* looking into the long-term outcome for stroke patients treated in stroke units (SU) compared with patients treated in general wards (GW), the mortality rate 5 years after the onset of stroke was 59.1% in the patients treated in SU and 70.9% in those treated in the GW. How many patients need to be treated in stroke units to prevent one additional death?
NNT = _______ (If you want to compare your answer with ours, click here.)
