This economics note is misleading

EDITOR—The series of occasional notes on economics has undoubtedly helped clinicians to understand the key concepts and jargon used by economists. The note discussing the use of outcome measures in economic evaluation is, however, misleading.1

Firstly, condition specific outcome measures and generic quality of life scales should not, in general, be used in cost effectiveness analysis.2 The primary reason for this is that such scales do not have the requisite interval properties. The scores produced by the short form-36 questionnaire (SF-36), for example, are little more than transformed ordinal rankings.

Even if interval properties can be shown, the use of generic quality of life scales in cost effectiveness analysis is severely restricted by their production of a set of scores reflecting different domains of health. For example, if the SF-36 is used in an evaluation, it can produce conflicting cost effectiveness ratios …