Validation of the Investigator Global Assessment of Chronic Hand Eczema (IGA-CHE): a new clinician reported outcome measure of CHE severity

The Investigator Global Assessment of Chronic Hand Eczema (IGA-CHE) is a novel Clinician-Reported Outcome measure that allows investigators to assess cross-sectional CHE global disease severity using clinical characteristics of erythema, scaling, lichenification/hyperkeratosis, vesiculation, oedema, and fissures as guidelines for overall severity assessment. This study aimed to evaluate the psychometric properties of the IGA-CHE for use as an outcome measure in CHE clinical trials and clinical practice. Psychometric analyses were performed using data from a sample of 280 patients with moderate to severe CHE from a phase 3 trial of delgocitinib cream, pooled across treatment groups. Test-retest reliability results were moderate to strong with kappa coefficients ranging from 0.63 to 0.76. Correlations with measures assessing related concepts were moderate or strong (range 0.65-0.72) and exceeded a priori hypotheses, providing evidence of convergent validity. Known-groups validity was supported by statistically significant differences between severity groups (< 0.001). Within-group effect sizes were consistently larger for improved groups compared to stable groups, providing evidence of ability to detect change. Anchor-based analyses generated within-subject meaningful change estimates ranging from - 0.8 to - 2.3. A correlation weighted average suggested a single value of - 1.7 in change from baseline. These findings provide evidence the IGA-CHE scale has strong reliability, construct validity, and ability to detect change, supporting its use as an endpoint in CHE clinical trials and clinical practice. Based on the evidence, 2-level changes in IGA-CHE score are considered a conservative meaningful change threshold; however, findings also indicate 1-level change in IGA-CHE scores reflects a clinically meaningful improvement for patients.