The Objective Buttocks Assessment Scale (OBAS): a new and complete method to assess the gluteal region

Introduction: New treatment methods to improve and enhance buttocks appearance require globally accepted scales for aesthetic research and patient evaluation. The purpose of our study was to develop a set of grading scales for objective assessment of the gluteal region and assess their reliability and validity. Materials and methods: Twelve photonumeric grading scales were created. Eleven aesthetic experts rated photographs of 650 women in 2 validation sessions. Responses were analyzed to assess inter-rater and intra-rater reliability. The Rasch model was used as part of the validation process. Results: All the scales exceeded criteria for acceptability, reliability and validity. Overall inter-rater reliability and intra-rater reliability were both “almost perfect” (p=0.15 and p=0.16 respectively). Conclusion: Consistent outcomes between raters and by individual raters at 2 time points confirm the reliability of the Objective Buttocks Assessment Scale in female patients and suggest it will be a valuable tool for use in research and clinical practice.