How to interpret the number needed to treat for clinicians

2025/08/21 by Nicholas C Chesnaye, Alberto Ortiz, Alberto Ortíz +8
Economics, Econometrics and Finance · Mathematics · #Advanced Causal Inference Techniques #Health Systems, Economic Evaluations, Quality of Life #Statistical Methods in Clinical Trials

paper · pdf · doi:10.1093/ndt/gfaf168

openalex publication_date 2025/08/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04

Abstract

The number needed to treat (NNT) is an intuitive tool for evaluating intervention effectiveness, and plays a valuable role in informed medical decision-making. This paper explains the calculation of NNT for risks estimated using both binary and time-to-event data, and introduces related concepts such as the number needed to harm (NNH) and the likelihood to be helped or harmed. To ensure accurate interpretation, we address common pitfalls associated with NNT, and provide guidance for its correct application in clinical research, highlighting the importance of considering baseline risk, time, and confidence intervals when interpreting the NNT.

Citations

• The Analysis of Failure Times in the Presence of Competing Risks

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