Validation of the Hidradenitis Suppurativa Investigator Global Assessment: A Novel Hidradenitis Suppurativa-Specific Investigator Global Assessment for Use in Interventional Trials

Importance: Few simplified instruments exist for use in hidradenitis suppurativa (HS) trials. Objective: To assess psychometric properties of the Hidradenitis Suppurativa Investigator Global Assessment (HS-IGA) score using a clinical trial data set. Design, Setting, and Participants: This retrospective analysis of a phase 2 randomized double-blind, placebo-controlled, active-reference arm trial (UCB HS0001) included adults with moderate-to-severe HS. Exposures: Trial participants were randomized at baseline to receive bimekizumab, adalimumab, or placebo. Main Outcomes and Measures: The HS-IGA score at prespecified time points up to 12 weeks after randomization. Results: The HS-IGA score showed strong convergent validity with IHS4 and HS-PhGA scores at baseline (Spearman correlation, 0.86 [P <.001] and 0.74 [P <.001], respectively) and at week 12 (Spearman correlation, 0.73 [P <.001] and 0.64 [P <.001], respectively). The HS-IGA scores assessed during predosing visits at screening and baseline showed good test-retest reliability (intraclass correlation coefficient [ICC] = 0.92). At week 12, HS-IGA responders were significantly associated with HiSCR-(50/75/90) responders (χ²= 18.45; P <.001; χ²= 18.11; P <.001; and χ²= 20.83; P <.001, respectively). The HS-IGA score was predictive of HiSCR-50/75/90 and HS-PhGA response at week 12 (AUC, 0.69, 0.73, 0.85, and 0.71, respectively). However, the HS-IGA as a measure of disease activity showed low predictive validity with patient-reported outcomes at week 12. Conclusions and Relevance: The HS-IGA score demonstrated good psychometric properties compared with existing measures and may be considered for use as an end point in clinical trials for HS..