Diagnostic Performance of Radiofrequency Echographic Multi Spectrometry Compared with Dual-Energy X-Ray Absorptiometry: A Real-World Study

Background: Radiofrequency Echographic Multi-Spectrometry (REMS) is an ultrasound-based technique for the assessment of bone mineral density (BMD) that has been proposed as an alternative to dual-energy X ray absorptiometry (DXA) for the diagnosis of osteoporosis. Although previous studies have reported high diagnostic concordance between REMS and DXA, evidence from real-world settings remains limited. The aim of this study was to evaluate the diagnostic performance and agreement between REMS and DXA in a clinical population undergoing BMD assessment. Methods: In this retrospective observational study, 145 subjects undergoing BMD evaluation were assessed with both REMS and DXA. Complete paired examinations were available for 142 patients at the lumbar spine and 134 at the femoral neck. DXA was used as the reference standard. Diagnostic performance of REMS was evaluated by calculating sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Agreement between REMS and DXA diagnostic classifications was assessed using linearly weighted Cohen’s kappa. Mean REMS and DXA measurements were compared using paired Student’s t-tests, whereas agreement between continuous BMD measurements was assessed using Bland–Altman analysis. Receiver operating characteristic (ROC) analysis was performed to evaluate the discriminative performance of REMS T-scores. Results: At the lumbar spine, REMS showed a sensitivity of 50.0% (95% CI: 37.5–62.5), specificity of 65.5% (95% CI: 54.8–74.8), PPV of 50.0% (95% CI: 37.5–62.5), and NPV of 65.5% (95% CI: 54.8–74.8). At the femoral neck, sensitivity was 40.0% (95% CI: 28.1–53.2), specificity 70.9% (95% CI: 60.1–79.7), PPV 48.9% (95% CI: 35.0–63.0), and NPV 62.9% (95% CI: 52.5–72.2). ROC analysis showed limited discriminatory performance for DXA-defined osteoporosis, with AUC values of 0.610 at the lumbar spine and 0.623 at the femoral neck. Linearly weighted Cohen’s kappa values were 0.225 and 0.183, respectively, indicating limited agreement in diagnostic classification. No statistically significant differences in mean BMD or T-score values were detected between the two techniques. Conclusions: In this real-world retrospective cohort, REMS and DXA showed no statistically significant differences in mean BMD or T-score values, but agreement in individual diagnostic classification was limited. These results suggest that REMS may have a complementary role alongside DXA rather than serving as a standalone screening method for DXA-defined osteoporosis in this cohort. Further prospective studies are needed to clarify the clinical significance of REMS–DXA discordant cases and their relationship with fracture risk.