10.122. Quality of Life: rating scale and time trade-off (QOL-Basic)

The QOL-Basic task provides a rating scale and a time trade-off measure.

For more detail, see QOL-SG.

10.123. Quality of Life: standard gamble (QOL-SG)

The QOL-SG task provides a standard gamble.

10.123.1. History and guide

Review articles:

• Torrance (1986), http://www.ncbi.nlm.nih.gov/pubmed/10311607 — includes references to validation of TTO method (against standard gamble, for states preferred to death).

• Torrance (1987), http://www.ncbi.nlm.nih.gov/pubmed/3298297; reviews SG/TTO/RS methods; RS is valid only after power-curve correction.

• Torrance & Feeny (1989), http://www.ncbi.nlm.nih.gov/pubmed/2634630, on QALYs and the use of utilities as the weight for them (defining cost–utility analysis, a subset of cost-effectiveness analysis).

• Guyatt et al. (1989), http://www.ncbi.nlm.nih.gov/pubmed/2655856.

10.123.2. Source

• Time trade-off and rating scale methods: Burström et al. 2006, http://www.ncbi.nlm.nih.gov/pubmed/16214258.

• Standard gamble: primarily from Torrance (1986, 1989), as above.

Some other relevant papers:

• Buitinga et al. (2012), http://www.ncbi.nlm.nih.gov/pubmed/22730908.

Note also the standard gamble method (Torrance 1986):

• Utility 0–1. Standard gamble method for chronic states preferred to death: alternative 1 is {probability p → health for the rest of one’s life (t years), probability 1 – p → instant death}; alternative 2 is the chronic state i for the rest of one’s life (t years). The probability p is varied until the subject is indifferent, at which point the utility is p, i.e. h_i = p.

• Standard gamble usually implemented with a visual aid for probabilities (e.g. proportions of a coloured wheel).

• Alternatives other than health/death possible, as long as one of the “alternative 1” options is preferred to the current state, and one is dispreferred to it.

• Utility < 0. For chronic states considered worse than death, the technique is modified: Alternative 1 is {p → health, 1 – p → current state}, alternative 2 is death; h = –p / (1 – p).

• For temporary health states, intermediate states are measured relative to the best state (healthy) and a worse/worst temporary state.

• Extension for utility > 1 (RNC addition). For chronic states considered better than normal health (potentially: mania), a logical extension is as follows. alternative 1 is {p → current state, 1 – p → dead}, alternative 2 is normal full health. If indifferent, p × h + (1 – p) × 0 = 1 × 1 ⇒ h = 1 / p.

• Internal consistency of SG versus modifications for prospect theory: Oliver (2003), http://www.ncbi.nlm.nih.gov/pubmed/12842320.

• What the SG measures, inc. the importance of the (typically ignored) time dimension: Gafni (1994), http://www.ncbi.nlm.nih.gov/pubmed/8005790.

Note regarding comparison between utilities/QALYs:

• Is a change in utility from 0.2–0.4 equal to a change from 0.6–0.8? Yes, under uncertainty: see http://www.ncbi.nlm.nih.gov/pubmed/17067192.

10.123.3. Intellectual property rights

Believed to contain no significant intellectual property, aside from the code, which is part of CamCOPS.