What Is the Best Method for Diagnosing Osteosarcopenic Adiposity in Women After Long-Term Bariatric Surgery? A Comparison and Validation of Different Criteria

Background/Objectives: To evaluate the agreement and discriminant validation of different osteosarcopenic adiposity (OSAd) diagnostic criteria in women post-Roux-en-Y gastric bypass (RYGB) surgery. Methods: Surgery. This is a cross-sectional study with women ≥2 years post-RYGB. OSAd was diagnosed using three criteria: Kelly for OSAd; ESPEN/EASO and SDOC for SO, associated with WHO osteopenia, respectively. Agreement was assessed with Cohen’s Kappa, and the predictive discriminatory capability was evaluated by sensitivity, specificity, and accuracy, using impairment of physical function and the increased risk of fracture as reference standards.; Results: A total of 178 women were evaluated, with a mean age of 45.2 ± 9.6 years old and postoperative time of 6.6 ± 3.6 years. The prevalence of OSAd was 2.2% [Kelly]; 2.8% [ESPEN/EASO + WHO]; 6.2% [SDOC + WHO]. Moderate agreement was found between Kelly and ESPEN/EASO (k = 0.658, p < 0.001), but agreement with SDOC was null (k = 0.104, p = 0.114). All criteria demonstrated high specificity (94.0–98.2%) and low sensitivity (0.0–16.7%), with Kelly showing the highest accuracy (92.7%); Conclusions: Among the evaluated criteria, Kelly presented the highest accuracy and 2.2% of OSAd prevalence. Despite consistently high specificity, all criteria exhibited low sensitivity. These findings highlight the need for more sensitive diagnostic approaches for OSAd in postoperative RYGB populations.