ABSTRACT
In 1988, Laupacis and co-workers published a paper in which they proposed the use of the reciprocal of the absolute risk reduction as a measure of effectiveness of therapies. They called this measure the number needed to treat (NNT) (Laupacis et al. 1988):
1/(DcDi)number needed to treat (NNT) (4)
In Figure 7.1, the risk of fatal outcomes after five years is about 44 per cent in the intervention group and 51 per cent in the control group. The
absolute risk reduction is then 7 per cent (51 per cent44 per cent7 per cent), or more precisely 6.4 per cent according to the publication (TorpPedersen and Kober 1999). This means that NNT is 1/0.06415.6.
