Measures of clinical severity, quality of life, and psychological distress in patients with psoriasis: a cluster analysis.

The impact of psoriasis on patients' quality of life may be quite destructive, and measures of disease status alone seem to have questionable validity in describing the true burden of illness. Our aim was to study, in patients with psoriasis, the relationship between classical measures of clinical status (i.e., PASI and SAPASI) and quality-of-life indexes (i.e., Skindex-29, Dermatology Life Quality Index, Psoriasis Disability Index, Impact of Psoriasis Questionnaire). In addition, two psychological distress indexes (i.e., Psoriasis Life Stress Inventory, 12-item General Health Questionnaire) were assessed. Data were collected between February 2000 and July 2001 at the inpatient wards of the Dermatological Institute IDI-IRCCS, Rome, Italy, in the framework of a large project on clinical, epidemiologic, emotional, and quality-of-life aspects of psoriasis. A cluster analysis of all the above-mentioned instruments was conducted on 786 eligible patients hospitalized with a diagnosis of psoriasis. Correlations between instruments were also analyzed in subsets of patients based on the main variables of interest. The instruments clustered in two distinct groups, one formed by clinical severity measurements and the other grouping all the quality-of-life and psychological indexes. The correlations between instruments observed in the subgroups determined by different sociodemographic and clinical variables showed the same pattern. In conclusion, the dissimilarity between clinical severity assessment and patient-centered measures stresses the need for a more comprehensive assessment of severity of psoriasis.