Measuring health-related quality of life and QALYs

A2.52 QoL is the other key dimension used in health-related appraisal. The two dimensions of longevity and QoL are aggregated in the concept of a QALY. As risks, and interventions to reduce them, can affect QoL as well as longevity, QALYs can reflect this additional dimension. QALYs are calculated by multiplying the change in QoL by the duration (in years) - for example a reduction in QoL from 1.0 to 0.5 for 6 months equals the loss of 0.25 QALYs. While not necessarily as straightforward as measuring length of life, measuring QoL can be undertaken with simple instruments such as questionnaires. The most widely used of these in the UK is the EQ-5D. This measures QoL in 5 dimensions:

mobility

ability to self-care

ability to carry out usual activities

pain/discomfort

anxiety/depression

A2.53 Each dimension is rated at one of 5 levels: no problems / slight problems / moderate problems / severe problems / extreme problems or unable. With 5 levels on 5 dimensions, EQ-5D is able to describe 3,125 (i.e. 55) "health states". Cardinal ratings for these health states - on a scale where 1 is equivalent to the best of health, and 0 to being dead - are available for the UK, based on the preferences of the population.

Ratings between 0 and 1 for different health states described by the EQ-5D tool are available from the EuroQol website

ideally the QoL ratings under the options being considered should, if possible, be sourced from people like those who would be affected (as commonly happens in clinical trials). However, if that is not feasible, QoL ratings for some common health states are available.33

monetary valuations of QALYs are available for the UK. The current monetary WTP value for a QALY is £60,000. Further information on the basis for the value of a QALY can be obtained by contacting the Department of Health and Social Care.

A2.54 Discounting of resources relating to health and life issues is carried out using the appropriate standard discount rate of 3.5% declining after 30 years. The value of VPFs, SLYs and QALY effects should be discounted at the health rate of 1.5%, declining after 30 years. See Annex 6 for further information on the discount rate.

A2.55 DALYs are a measure of life-years adjusted for loss of quality of life and loss of life expectancy for people living with a health condition or its consequences. Unlike life expectancy, which is measured by the area below profiles such as the survival curves illustrated above, DALYs measure a loss of longevity aggregated with loss of quality of life (the area above a curve). Appraisal of an intervention is concerned with estimating the difference that it makes - hence the intervention's impacts could be described in terms of QALYs gained or DALYs prevented. However, in practice, DALYs differ in some subtler ways and are used less often in the UK.

_________________________________________________________________________________

33 See for example Stouthard, M. E. A., et al (1997) "Disability weights for diseases in the Netherlands" Amsterdam: Inst. Sociale Geneeskunde.