Determining the minimal clinically important difference and responsiveness of the Dermatology Life Quality Index (DLQI): further data

Abstract

Aims: To determine the minimal clinically important difference (MCID) of the Dermatology Life Quality Index (DLQI) and its responsiveness to change in inflammatory skin diseases.

Methods: A longitudinal study: at stage 1, patients completed the DLQI and a disease severity global question; at stage 2, a global rating of change in quality of life (QoL; Global Rating of Change Questionnaire, GRCQ) was added and used as an anchor to measure the MCID of the DLQI.

Results: 192 patients completed stage 1 and 107 completed stage 2. The mean DLQI score at stage 1 was 9.8 and 7.4 at stage 2 with a mean change of 2.4 (p < 0.0001). 31 patients experienced a 'small change' in their QoL (±3 and ±2) on the GRCQ. The mean corresponding change in DLQI scores was 3.3, which is regarded as the approximate MCID.

Conclusions: Previous estimates of the MCID of the DLQI have varied from 3 to 5. Although this study demonstrated a MCID of 3.3, we recommend that the MCID in inflammatory skin diseases should be 4.