Reliability and Consistency of the IEC Ultrasound Staging System for Stage III Cellulite: An Image-Based Validation Study

Background. In recent years, the use of ultrasound in the diagnosis of cellulite has grown substantially, making reproducible and validated ultrasound-based grading systems for stage III cellulite increasingly necessary to support their accurate application in both clinical practice and research. The Intagliata Echo-Cellulite (IEC) staging system identifies three morphological sub-types using high-frequency ultrasound. Objective. The study aims to evaluate the inter-rater reliability and test–retest reliability of the IEC staging system. Methods. This prospective, image-based reliability study included 150 women with stage III cellulite at a single center. Standardized ultrasound images acquired by an expert were independently rated by two non-expert raters in two sessions four weeks apart and compared with the expert’s ratings; the expert is also the developer of the IEC system. Results. For the primary outcome, IEC stage, both raters achieved almost perfect inter-rater agreement with the gold standard (Rater 1: κ = 0.926, 93.3%; Rater 2: κ = 0.985, 98.7%) and almost perfect test–retest consistency (Rater 1: κ = 0.840; Rater 2: κ = 0.817). Agreement on secondary ultrasound-based variables was more heterogeneous and consistently lower than for the composite IEC stage. Limitations. The image-based design provides an upper bound reliability estimate; additionally, the gold standard rater is the developer of the IEC system, which constrains the independence of the reference standard. Conclusions. Even when applied by untrained raters, the IEC staging system shows high inter-rater reliability and test–retest consistency. These findings further independent validation as a standardized grading tool in cellulite research and precision aesthetic medicine.