The application of multiple quality-of-life instruments in individuals with mild-to-moderate psoriasis

The 36-item Short-Form Health Survey Questionnaire (HSQ SF-36), Psoriasis Disability Index (PDI), and Dermatology Life Quality Index (DLQI) were administered to individuals with mild-to-moderate psoriasis to validate the general quality-of-life instrument against the dermatosis-specific, and the dermatology-specific, disability measure. The population consisted of 644 adults with psoriasis involving up to 20% of the body surface area, who were enrolled in 2 US multicentre, evaluator-blinded, parallel-group clinical trials for a new psoriasis medication. Patients averaged 16.5% of maximum possible disability as measured by the PDI, and 23.4% of maximum possible disability as measured by the DLQI. Normalised T-scores showed that the patients approximated US population means on all 8 of the HSQ SF-36 dimensions. The HSQ SF-36 scales did not reflect substantial quality-of-life impairment, although all showed statistically significant correlations with both the PDI and DLQI (correlation coefficients ranging from -0.13 to -0.45). Moreover, while the disability indices were more responsive to psoriasis characteristics than the HSQ SF-36 quality-of-life scales, all 8 HSQ SF-36 dimensions demonstrated sensitivity to at least some objective and/or subjective ratings of severity. The strongest relationships were observed between the PDI, DLQI and the HSQ SF-36 Mental Health and Social Functioning dimensions, suggesting that the HSQ SF-36 is sensitive to psychosocial suffering related to psoriasis, which is not conveyed in objective clinical measures of severity.