Sensitivity of the Dermatology Life Quality Index to clinical change in patients with psoriasis

Background Quality of life is increasingly recognized as an important outcome measure in dermatology. The Dermatology Life Quality Index (DLQI) is a self-administered questionnaire designed to measure the impact of skin diseases on patients' quality of life. Objectives To assess the responsiveness of the DLQI to variations in clinical status as measured by the Self-Administered Psoriasis Area and Severity Index (SAPASI) in a large sample of in-patients with psoriasis. Methods The SAPASI and the DLQI were completed by 359 in-patients with psoriasis at hospital admission and 4 weeks after discharge. Changes in SAPASI scores were used to categorize patients as improved, unchanged or worsened. Next, these groups were compared with one another with regard to the change in DLQI scores. Results Four weeks after discharge, both mean SAPASI scores and mean DLQI scores were significantly lower than at admission ( P < 0.001). In improved patients, the DLQI score decreased significantly more than in worsened patients ( P < 0.001), and tended to decrease more than in unchanged patients (P = 0.07). The difference in DLQI score change between improved patients and unchanged or worsened patients grouped together was highly significant ( P < 0.001); also, it remained significant or nearly significant when the analysis was performed on subsets of patients based on gender and age range. Conclusions This study contributes to building evidence of validity for the DLQI, because the instrument demonstrated the ability to detect small but meaningful changes in clinical status over time in a large sample of patients with psoriasis.