12. Quality-Adjusted Survival
Published Online: 8 MAR 2002
Copyright © 2000 John Wiley & Sons, Ltd
Quality of Life: Assessment, Analysis and Interpretation
How to Cite
Fayers, P. M. and Machin, D. (2002) Quality-Adjusted Survival, in Quality of Life: Assessment, Analysis and Interpretation, John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/0470846283.ch12
- Published Online: 8 MAR 2002
- Published Print: 18 APR 2000
Print ISBN: 9780471968610
Online ISBN: 9780470846285
- visual analogue rating scales (VAS);
- time trade-off (TTO);
- multi-attribute utility measures;
- utility-based instruments;
- quality-adjusted life years (QALYs);
- sensitivity analysis
The overall survival time following diagnosis in a patient with a life-threatening disease may be considered as partitioned into distinct periods during which the QoL levels of the patient may expect to differ. Once the time in each of these states is determined, they can be used to calculate the time without symptoms and toxicity (TWiST); the time actually experiencing symptoms and/or toxicity (TOX): and the time in relapse following progression of the disease (PROG).
Utility coefficients (once defined) corresponding to each of these states can be used as multipliers of TOX, TWiST and PROG to obtain a weighted quality-adjusted time without symptoms and toxicity (Q-TWiST). These are then averaged over all patients receiving a particular treatment and so can be used to compare treatments.
Threshold analysis enables the investigations of how sensitive the difference in treatments so quantified is on the values of the utility coefficients of each state. The way in which Q-TWiST may be compared between different prognostic groups, and changes over successive time intervals from diagnosis, are described.