EASI, (objective) SCORAD and POEM for atopic eczema: responsiveness and minimal clinically important difference

Demonstration of adequate reliability and validity is sufficient for concluding that an instrument is applicable for descriptive and predictive purposes, but before we can confidently use an outcome measure in clinical trials, the responsiveness (synonymous with sensitivity to change) and minimal clinically important difference (MCID) should be known. With this study, we aimed to assess responsiveness and MCID of four outcome measures used in atopic eczema: the Severity Scoring of Atopic Dermatitis (SCORAD), the objective SCORAD, Eczema Area and Severity Index (EASI), and the Patient-Oriented Eczema Measure (POEM).

Data of three randomized controlled trials were used. To demonstrate responsiveness, we plotted receiver operating characteristic (ROC) curves. MCID was estimated using mean change scores of patients that showed a relevant improvement. Bland and Altman methods were used to quantify the limits of agreement.

Area under the ROC curve for the SCORAD was 0.70 [95% confidence interval (CI): 0.61-0.78], for the objective SCORAD, 0.73 (95% CI: 0.70-0.77), for the EASI, 0.67 (95% CI: 0.60-0.76), and for the POEM, 0.67 (95% CI: 0.59-0.75). Scores above 0.70 represent a fair responsiveness. The MCID was 8.7 points for the SCORAD, 8.2 for the objective SCORAD, 6.6 for the EASI, and 3.4 for the POEM.

The objective SCORAD and SCORAD showed a fair responsiveness. The MCIDs are an important prerequisite for the interpretation of published eczema trials and for the planning/sample size estimation of future trials.