Development and Validation of a Photonumeric Scale for Evaluation of Static Horizontal Forehead Lines

BACKGROUND A validated scale is needed for objective and reproducible comparisons of static forehead lines before and after treatment in practice and clinical studies. OBJECTIVE To describe the development and validation of the 5-point photonumeric Allergan Forehead Lines Scale. METHODS The Allergan Forehead Lines Scale was developed to include an assessment guide, verbal descriptors, morphed images, and real subject images for each scale grade. The clinical significance of a 1-point score difference was evaluated in a review of multiple image pairs representing varying differences in severity. Interrater and intrarater reliability was evaluated in a live-subject validation study (N = 295) completed during 2 sessions occurring 3 weeks apart. RESULTS A difference of >= 1 point on the scale was shown to reflect a clinically significant difference (mean [95% confidence interval] absolute score difference, 1.06 [0.91-1.21] for clinically different image pairs and 0.38 [0.26-0.51] for not clinically different pairs). Intrarater agreement between the 2 live-subject validation sessions was almost perfect (mean weighted kappa = 0.87). Interrater agreement was almost perfect during the second rating session (0.86, primary end point). CONCLUSION The Allergan Forehead Lines Scale is a validated and reliable scale for physician rating of static horizontal forehead lines.