Comparison of Skindex-29, Dermatology Life Quality Index, Psoriasis Disability Index and Medical Outcome Study Short Form 36 in patients with mild to severe psoriasis

BACKGROUND: Severity assessment of patients with psoriasis is a critical issue. Classical clinical assessment has recently been combined with quality of life (QoL) scores, but several instruments are used. Moreover, studies have focused on patients with moderate to severe psoriasis. OBJECTIVES: To compare the characteristics of QoL instruments in patients with the full range of psoriasis severity attending dermatology clinics. METHODS: Observational, prospective, multicentre study. Patients completed Skindex-29 (anchor) and a second instrument randomly selected from Dermatology Life Quality Index (DLQI), Psoriasis Disability Index (PDI) and Medical Outcome Study Short Form 36 (SF-36). RESULTS: Demographic data, Psoriasis Area and Severity Index and affected body surface area were not different between the three groups. Skindex-29 showed a weak but significant correlation with clinical severity; only PDI showed similar correlation. PDI, DLQI and SF-36 showed a substantial floor effect in patients with mild to severe psoriasis. Skindex-29 showed strong correlations with the other three QoL instruments. SF-36 was more sensitive than the other instruments in detecting worse QoL in male patients. CONCLUSIONS: Skindex-29 has better sensitivity to clinical severity with minimal floor effect, and covers the main domains explored by the other three QoL instruments in patients with mild to severe psoriasis.