A scale for the objective measurement of severity of psoriasis is presented for application to long-term studies of the course of the disease and possible related factors. A group of dermatologists and a group of hospitalized patients ranked a series of 50 features of psoriasis on a self-anchoring scale ranging from 1 to 7 with 1 as indicative of mildest possible psoriasis and 7 as indicative of worst possible psoriasis. A final scale of features with low variance was constructed. Differences between objective and subjective evaluation of severity are stressed.
Baughman RD, Sobel R. PsoriasisA Measure of Severity. Arch Dermatol. 1970;101(4):390-395. doi:10.1001/archderm.1970.04000040012004