UT-NNT (Utility and Time adjusted Number Needed to Treat)

1. Description

UT-NNT (Utility and Time adjusted NNT) adjusts the BR event probabilities in NNT for the time saved or lost due to treatment and the utilities associated with the treatment.[1] UT-NNT is calculated from the reciprocal of the difference between the two "incremental" benefits and "incremental" risks as in INHB. The adjustment for time is made by multiplying time saved or lost due to treatment by the probabilities of benefits or risks. Adjustment for utilities is made in the same way.

2. Evaluation

2.1 Principle
  • UT-NNT can deal with multiple criteria through weighted summation of criteria.
  • UT-NNT provides a way to incorporate value judgements.
  • The reciprocal of the product of utilities and probabilities (i.e. expected utilities) is interpreted in the same way as in NNT.

2.2 Features
  • UT-NNT can integrate benefit and risk into a single measure for analysis.
  • It was argued to be superior to NNT due to its ability to incorporate the time dimension as well as utilities (see comment above in Principle of UT-NNT).
2.3 Visualisation
  • Visualisations similar to the one used in NNT may be used.

2.4 Assessability and accessibility
  • The parameters and interpretation of UT-NNT are simple but contradict decision theory, because the reciprocal of utility does not have the same meaning as the reciprocal of probability.

3. References

[1] Riegelman R, Schroth WS. Adjusting the number needed to treat: incorporating adjustments for the utility and timing of benefits and harms. Med Decis Making 1993 Jul;13(3):247-52..