the use of mapping methods to estimate health state utility values

• The model should be validated. Ideally this would be conducted using an external
sample similar to the target sample. However it is unlikely that this will be available
in many cases. Where the sample size is large enough to do so, it is recommended that
the sample is randomly split to provide an estimation subsample and validation
sample. The final model specification can then be re-estimated using the full sample.
• If there is no overlap in content between the measures of interest, mapping is unlikely
to be able to appropriately capture the relationship to estimate health-related utility.
Alternative methods for estimating health-related utility data should be considered in
these circumstances.
The main advantage of mapping is that it enables outcomes data collected in a trial or
observational study to be used in economic evaluation to meet the NICE reference case, even
if the main source trial or study did not include the EQ-5D. However, in most cases it is still
preferable to obtain directly collected data within studies of effectiveness. Whereas most
NICE submissions that have used mapping have used condition-specific measures of health
related quality of life or clinical indicators of disease severity to predict EQ-5D scores for
patients, the majority of published literature has focused on mapping between generic
measures using general population samples. Whilst there are areas of uncertainty in the most
appropriate methods for mapping, there is a significant amount of active research currently
being conducted in this area and we hope that these will be resolved in the near future.
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