Mapping / Transformations

AQoL Transformations



Multi-Instrument Comparison study transformations

The Multi-Instrument Comparison study allowed mapping to be calculated between multi-attribute utility instruments.

Each instrument has a set of 5 equations that allow transformed scores to be calculated for comparison.

Please note that these equations are subject to review, may be changed at any time.

Notes regarding transformations between utility instruments

Transformations do not allow the substitution of one instrument for another.

Their purpose is to adjust scores, as far as possible, for differences in the content of instruments. But adjustment is necessarily incomplete.

Consider a health state made up of the various dimensions in Box 1 and outlined according to the descriptive system of the HUI-3 and EQ-5D. The health state includes difficulty with vision and hearing. Omission of vision and hearing from the EuroQoL (EQ-5D) results in a high utility score of 0.8. The HUI which places considerable weight on vision and hearing gives a score of 0.14 to the same individual. (With vision and hearing omitted the HUI score would have scored 0.74). No transformation of the EQ-5D could achieve the HUI-3 result because the base data concerning vision and hearing is not collected by the EQ-5D.

At best, a transformation will alter the relative importance of dimensions which do exist. If the single question relating to emotional state in the EQ-5D underrates its importance then the relative weight might be increased in a transformation from the EQ-5D to the AQoL-8D.

Transformations comparison table

Source: Hawthorne G, Richardson J and Day NA. 2001, ‘A comparison of the assessment of quality of life (AQoL) with four other generic utility instruments’, Annals of Medicine, vol 33, no 5, pp 358-370.

To date, transformations are only available between AQoL-4D and 6D. Transformations between all the instruments in the AQoL suite will be available soon.