This workshop is given on behalf of the Statistical Methods Group.

Workshop type: Training.

Objective: To provide review authors with the knowledge and skills needed to calculate numbers needed to treat (NNTs) from trial reports, to verify whether reported NNTs are adequate and to interpret the results.

Summary:
The number needed to treat (NNT) is widely used to present the results of clinical trials. However, incorrect calculations, misuse in specific study situations and misleading interpretation of the results are not uncommon in practice, especially in the situation of survival time data.

This workshop will provide an introduction to the use and interpretation of NNTs as an effect measure in clinical trials and systematic reviews. We will discuss, in particular, the limitations of NNTs including problems associated with the inconvenient scale, the sensitivity to changes of the b aseline risk and the dependence on the follow-up time.

Small group practical work will be an integral part of the workshop focusing on adequate calculation and interpretation of point and interval estimates of NNTs in practical examples. Participants should bring pocket calculators, pens and paper.

Reference:
Bender R. Number needed to treat (NNT).  In: Armitage P, Colton T (eds). Encyclopedia of Biostatistics (2005), pp. 3752-3761. Chichester: Wiley.

Intended audience: (i) Review authors; (ii) readers of medical literature.

Technical level expected of participants: Basic/Intermediate.