CONCISE COMMUNICATION BJD British Journal of Dermatology 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 P. Fernandez-Pen ˜as,* M. Jones-Caballero,* O. Espallardoà and A. Garcı ´a-Dı ´ez* *Department of Dermatology, Hospital Universitario de la Princesa, Madrid, Spain  Department of Dermatology, Westmead Hospital, Sydney Medical School – Westmead, The University of Sydney, Westmead, NSW 2145, Australia àMerck-Serono, Madrid, Spain Correspondence Pablo Fernandez-Pen ˜as. E-mail: pfernandezpenas@med.usyd.edu.au Accepted for publication 27 December 2011 Funding sources This study was supported financially by Merk- Serono S.A. Conflicts of interest O.E. was an employee at Merk-Serono at the time of this study. She is no longer affiliated with the company. DOI 10.1111/j.1365-2133.2012.10806.x Summary 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 instru- ments 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. Severity assessment plays a major role in tailoring treatments to patients. Classically, severity has been measured clinically, 1 but dermatologists are aware that the impact of diseases on the quality of life (QoL) of patients is another important fac- tor. 2 There are several well-known QoL instruments in derma- tology, that have recently been critically reviewed. 3 In psoriasis, a review has suggested the suitability of Skindex-29 and Medical Outcome Study Short Form 36 (SF-36); 4 others indicate that there is not enough evidence to use Skindex-29, 5 and some guidelines recommend use of the Dermatology Life Quality Index (DLQI). 6 On the other hand, most studies have focused on moderate to severe psoriasis, but very few papers have addressed QoL in the full span of severity. 7 We have decided to compare four QoL instruments in patients with mild to severe psoriasis attending dermatology clinics. Materials and methods In this observational, prospective, multicentre study, patients were randomly assigned to one of three groups to fill out two QoL instruments. Skindex-29 was the common instrument (anchor). The second instrument was the Psoriasis Disability Index (PDI), DLQI or SF-36. Patient selection Patients with psoriasis, regardless of severity, were included in the study, better to match the use of the instruments in general dermatology clinics. Patients had to be at least 18 years old and able to read and write. Oral witnessed informed consent was obtained before screen- ing. Ó 2012 The Authors 884 BJD Ó 2012 British Association of Dermatologists 2012 166, pp884–887