Impact of psoriasis on quality of life in Iran.

Background: The Psoriasis Disability Index (PDI) questionnaire is a widely used instrument to measure psychological morbidity in plaque-type psoriasis patients.

Aims: This study aimed to validate the Persian version of the PDI and to evaluate the impact of psoriasis on quality of life (QOL).

Methods: The English language version of the PDI was translated into Persian (Iranian official language) and was used in this study. The questionnaire was administered to a consecutive sample of 125 chronic plaque-type psoriasis patients and statistical analysis was performed to evaluate the impact of psoriasis on QOL. The other health-related QOL assessment tool included the Persian version of the Dermatology Life Quality Index (DLQI).

Results: Overall, 125 patients who had received the PDI and DLQI completed all the questions. Reliability analysis showed a satisfactory result (Cronbach's a coefficient=0.92 and 0.79 for PDI and DLQI, respectively). There was a strong statistical correlation between mean PDI and DLQI scores, with mean Psoriasis Area and Severity Index (PASI) (P=0.005 and 0.02). Also, a significant correlation coefficient existed between DLQI and PDI (r=0.94). The higher the PASI index, the higher the PDI and DLQI scores, which indicated greater impact on QOL. In the patients with lesions on visible exposed skin areas, the correlation was statistically significant (P=0.002 and 0.01).

Conclusion: The Persian PDI is an acceptable, reliable and valid measure of psychological distress, with more suitable content validity than DLQI for assessment of impact of psoriasis on QOL among psoriasis patients. Data provided may improve the physicians' awareness of the importance of the patients' QOL.