Measuring quality of life of patients with different clinical types of psoriasis using the SF-36.

BACKGROUND: Different specific and generic instruments are used to evaluate quality of life in dermatology, but their interrelationship is not well known.

OBJECTIVES: To describe the quality of life in patients with different clinical types of psoriasis using the 36-item short form of the Medical Outcomes Study questionnaire (SF-36), and to study its correlation with dermatology-specific instruments.

METHODS: We conducted a cross-sectional study of 380 inpatients with psoriasis. SF-36 mean scores were compared with the norms for medical and psychiatric disorders. Quality of life was also measured by both dermatology-specific (Skindex-29 and Dermatology Life Quality Index, DLQI) and psoriasis-specific instruments (Psoriasis Disability Index, PDI, and the Impact of Psoriasis Questionnaire, IPSO). A specific (Psoriasis Life Stress Inventory, PLSI) and a generic (12-item General Health Questionnaire, GHQ-12) measure of psychological distress was also used. A cluster analysis was performed to study the relationship among the different questionnaires.

RESULTS: Our study population showed SF-36 physical health scores similar to minor medical conditions (e.g. physical functioning 79 for psoriasis, 80 for minor medical conditions, and 57 for severe medical conditions), but mental health scores quite similar to psychiatric illnesses (e.g. mental health 57 for psoriasis, 81 for minor medical conditions, 79 for severe medical conditions, and 53 for psychiatric conditions). The SF-36 showed two distinct patterns of impairment of quality of life, with a greater burden of disease for palmoplantar, pustular and arthropathic psoriasis. SF-36 scales tended to form separate clusters from the other dermatology-specific quality of life instruments.

CONCLUSIONS: A generic quality of life instrument (e.g. the SF-36) provides information that is complementary to that derived from dermatological questionnaires, and may give further insight in the evaluation of the burden of psoriasis.