Background:
Several questionnaires have been used to measure health related quality of life (HRQoL) inpatients with psoriasis, few have been adapted for use in Spain; none of them was developedspecifically for the Spanish population. The purpose of the study was to validate and assessthe sensitivity to change of a new questionnaire to measure HRQOL in patients with psoriasis(PSO-LIFE).
Methods:
Observational, prospective, multicenter study performed in centers around Spain. Patientswith active or inactive psoriasis completed the PSO-LIFE together with other DermatologyQuality of Life Index (DLQI) and Psoriasis Disability Index (PDI). A control group ofpatients with urticaria or atopic dermatitis was also included. Internal consistency and testretestreliability of the PSO-LIFE were assessed by calculating Cronbach’s alpha andIntraclass Correlation Coefficient (ICC). Validity was assessed by examining factorialstructure, the capacity to discriminate between groups, and correlations with other measures.Sensitivity to change was measured using effect sizes.
Results:
The final sample included for analysis consisted of 304 patients and 56 controls. Mean (SD)age of psoriasis patients was 45.3 (14.5) years compared to 38.8 (14) years for controls(p < 0.01). Cronbach’s alpha for the PSO-LIFE was 0.95 and test-retest reliability using theICC was 0.98. Factor analysis showed the questionnaire to be unidimensional. Mean (SD)PSO-LIFE scores differed between patients with psoriasis and controls (64.9 [22.5] vs 69.4[17.3]; p < 0.05), between those with active and inactive disease (57.4 [20.4] vs 76.4 [20.6];p < 0.01), and between those with visible and non-visible lesions (63.0 [21.9] vs. 74.8 [23.9];p < 0.01). The correlation between PSO-LIFE and PASI scores was moderate (r = 0.43)while correlations with DLQI and PDI dimensions ranged from moderate to high (between0.4 and 0.8). Effect size on the PSO-LIFE in patients reporting ‘much improved’ health statusat study completion was 1.01 (large effect size).
Conclusions:
The present results provide substantial support for the reliability, validity, and responsivenessof the PSO-LIFE questionnaire in the population for which it was designed.