RV-NNH (Relative Value adjusted Number Needed to Harm)

1. Description

RV-NNH (Relative Value adjusted NNH) incorporates stakeholders' value preferences or "relative values" on the importance of AEs into NNH.[1] Relative value is defined as the ratio of risk utility to benefit utility. RV is then multiplied by the absolute risk difference of a particular AE to give RV-NNH. It's focus is on risk.

2. Evaluation

2.1 Principle

• A composite RV-NNH for multiple AEs can be derived by taking the reciprocal of the sum of the products of absolute risk difference for particular risks and their relative values.

• The sum of the probabilities in the composite RV-NNH has an infinite upper bound.

• The RV-NNH metric may approach zero contributing to implausible interpretation.

2.2 Features

• RV-NNH does not properly integrate benefit and risk into a single measure.

• It only penalises the excess risk through the relative values.

2.3 Visualisation

• Visualisations similar to the one used in NNT may be used.

2.4 Assessability and accessibility

• Although the required data are straightforward, the source of the rates/probabilities can be questionable due to the quality of data sources and may be biased.

3. References

[1] Guyatt GH, Sinclair J, Cook DJ, Glasziou P. Users' guides to the medical literature: XVI. How to use a treatment recommendation. Evidence-Based Medicine Working Group and the Cochrane Applicability Methods Working Group. JAMA 1999 May 19;281(19):1836-43.