Table 3.

Attributes of good diagnostic criteria for comparing groups in research.

Must be valid, i.e. must measure what they are meant to measure

Repeatable: one person using the criteria should come up with the same answer as when another person uses them

Reflect some degree of morbidity: needed to avoid subclinical disease such as defining acne on the basis of a few comedones, which is physiological during puberty

Coherent with clinical concepts: they should correspond with what dermatologists consider the condition to be

Simple to use: essential when describing large numbers of people

Good applicability to different people, including skin colour, older or very young skin, and that are culturally sensitive