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The 'number need to treat': does it help clinical decision making?
1Department of Social Medicine, University of Bristol, Canynge Hall, Whiteladies Road, Bristol BS8 2PR, UK.
Journal of Human Hypertension
|December 1, 1999
Summary
The number needed to treat (NNT) is a useful metric, but it changes based on patient risk and clinical context. Calculating NNT requires careful consideration of relative risk reduction across different baseline risk populations.
Area of Science:
- Clinical Epidemiology
- Biostatistics
Background:
- The number needed to treat (NNT) is a widely used metric for quantifying treatment efficacy.
- NNT values are sensitive to variations in baseline patient risk, clinical settings, and outcome measures.
- Geographic and temporal factors can introduce instability into NNT calculations.
Purpose of the Study:
- To highlight the variability and limitations of the number needed to treat (NNT).
- To provide guidance on the appropriate calculation and interpretation of NNT.
- To emphasize the importance of considering baseline risk when presenting treatment effects.
Main Methods:
- The study reviews the factors influencing NNT variability.
- It discusses the challenges in deriving NNT from meta-analyses, particularly pooled absolute risk differences.
- The proposed method involves applying relative risk reduction to diverse baseline risk populations.
Main Results:
- NNT is highly dependent on the baseline risk of the patient population.
- Pooled absolute risk differences in meta-analyses can lead to unstable NNT estimates.
- Geographic and secular trends further complicate NNT interpretation.
Conclusions:
- NNT calculations require careful consideration of patient baseline risk.
- A recommended approach is to apply relative risk reduction to populations with specified high, average, and low absolute risks.
- This method provides a more nuanced and informative range of possible NNTs.