Background: A validated scale is needed for objective and reproducible comparisons of horizontal neck lines before and after treatment in practice and clinical studies. Objective: To describe the development and validation of the 5-point photonumeric Allergan Transverse Neck Lines Scale. Methods: The Allergan Transverse Neck 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 rating validation study (N = 297) 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, 1.22 [1.09-1.35] for clinically different image pairs and 0.57 [0.42-0.72] for not clinically different pairs). Intrarater agreement between the 2 live-subject rating validation sessions was substantial (mean weighted kappa = 0.78). Interrater agreement was substantial during the second rating session (0.73, primary end point). Conclusion: The Allergan Transverse Neck Lines Scale is a validated and reliable scale for rating of severity of neck lines.
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