Composite multi-dimensional constructs, such as ‘global mental health’ and ‘global physical health’, in PROMIS® instruments and ICHOM standard outcome sets, are formative, not reflective. Their preference-insensitivity means they are potentially misleading in both clinical and policy decision making practice. Their frequent validation by reflective psychometric tests is also improper methodologically. The spread of these instruments is occurring without sufficient awareness on the part of patients, clinicians, researchers and policy makers that the need for group-specific preference bases (‘tariffs’) for such measures rules out any possibility of ‘international gold standard metrics’.