Validation is a complex issue (see What is Validation). The validity of an MAU instrument requires four types of achievable evidence. These relate to:

(i) The instrument descriptive system or questionnaire. Importantly, content validity may be context specific.

(ii) The instrument model: does the model which combines items achieve criterion validity: does it result in the same utility prediction as the holistic measurement of the same health state using the same utility scaling instrument.

(iii) The measurement of utility: does the scaling instrument (SG, TTO, etc) measure what we want to measure (see Validating utility).

(iv) The instrument utility scores: Does the instrument produce scores with predictive and convergent validity (correlate with other ‘validated’ scales)?  Again, the answer may be context specific as with the scores from other QoL instruments.