The Hyperhidrosis Disease Severity Measure-Axillary: Conceptualization and Development of Item Content

Introduction: Patients with primary axillary hyperhidrosis (AHH) suffer from a variety of symptoms. Improved patient-reported outcome (PRO) measures are needed to better assess and categorize the severity of AHH symptoms experienced by patients because the widely used Hyperhidrosis Disease Severity Scale (HDSS) is a single-item measure that cannot capture the broad scope of disease impact. Methods:The Hyperhidrosis Disease Severity Measure Axillary (HDSM-Ax) was developed for determining the severity of excessive sweating in patients with primary focal AHH based on face-to-face concept elicitation interviews with 58 AHH patients, a literature review, and expert clinical input. Two waves of face-to-face cognitive interviews (n=26 and n=27) were conducted to evaluate HDSM-Ax clarity and relevance. Additional interviews (n=5) were conducted to confirm content. Adding Rasch MeasurementTheory (RMT) analyses allowed for an iterative streamlined approach to documenting content validity and other cross-sectional measurement properties of the new HDSM-Ax measurement. Results:The 11-item HDSM-Ax PRO scale (0-4 scale per item; 0-44 total scale) represents an AHH symptom range of 0 (no sweating) to 44 (worst possible sweating). Content validity of the HDSM-Ax was documented by showing that chronologically-grouped interviews demonstrated saturation in AHH symptom severity concepts. Cognitive debriefing interviews provided evidence that item content is complete, comprehensible, meaningful, and relevant. RMT-based exploration indicated that targeting of the HDSM-Ax was adequate, suggesting good matching between items and persons; item fit was adequate, suggesting a clinically cohesive scale; and items appeared to be stable between subgroups, thereby supporting a summary score. Conclusions: The HDSM-Ax is a well-developed measure of AHH severity based on patient-reported signs and symptoms. It is a superior measure to the HDSS and can be used in clinical research and clinical practice to quantify changes in symptom severity in response to treatment.