Development and validation of a new clinically-meaningful rating scale for measuring lateral canthal line severity.

BACKGROUND Several scales have been employed for evaluating the effects of cosmetic treatments in the periorbital area. The Food and Drug Administration (FDA) has recently issued new recommendations specifying a rigorous process to validate new aesthetic scales. OBJECTIVES The authors describe and validate a new clinical rating scale: the Investigator's Global Assessment of Lateral Canthal Line (IGA-LCL) severity scale. METHODS The new FDA recommendations were utilized to validate the new scale. The first step was concept elicitation (based on direct input from clinicians, patients, and literature) and evaluation of content validity (appropriateness of concepts). The resulting five-point scale provided detailed descriptions of the lateral canthal lines (LCL), including quantitative assessment of LCL length and depth. Performance parameters, including intra- and interrater reproducibility and construct validity, were then evaluated in clinical studies. Finally, the scale's threshold for clinically-meaningful benefit and the ability of the scale to detect change were confirmed in two Phase 2b clinical studies involving a total of 270 subjects. RESULTS Content validity was established and the IGA-LCL scale showed excellent interrater reliability (weighted Kappa = 0.89) and interrater reliability (weighted Kappa = 0.77; Kendall's coefficient of concordance = 0.89). In clinical trials, the scale was sensitive enough to detect clinically-meaningful one- and two-point changes in LCL severity following treatment with topical botulinum toxin type A (BoNT-A). The authors observed statistically-significant correlations between the physician-rated IGA-LCL results and patient-reported outcomes. CONCLUSIONS The IGA-LCL scale was shown to be reliable, appropriate, and clinically meaningful for measuring LCL severity.