Routine Laboratory Markers as Incremental Predictors Beyond OSTA for Dual-Energy X-Ray Absorptiometry-Defined Osteoporosis: Internal Validation in a Referral Cohort

Background and Objectives: Routine laboratory markers may support diagnostic risk stratification for osteoporosis, but their incremental value beyond the Osteoporosis Self-Assessment Tool for Asians (OSTA) remains uncertain in referral-based practice. We evaluated whether serum uric acid, albumin, alkaline phosphatase (ALP), and systemic inflammatory indices improve prediction of DXA-defined osteoporosis beyond OSTA in postmenopausal women. Materials and Methods: This retrospective cross-sectional study included 3504 postmenopausal women referred for DXA between January 2021 and May 2025. Osteoporosis was defined as the lowest T-score ≤ −2.5 at the lumbar spine, total hip, or femoral neck. Sequential exclusions removed patients with chronic hepatobiliary disease, chronic systemic inflammatory disease, bone-active medication exposure, systemic glucocorticoid use, abnormal liver biochemistry, or missing required variables. Multivariable logistic regression assessed associations, and OSTA-based prediction models were internally validated using stratified 10-fold cross-validation. Results: Osteoporosis was present in 1660 women (47.4%). Higher BMI, uric acid, and albumin were independently associated with lower odds of osteoporosis, whereas ALP and calcium were associated with higher odds. OSTA alone achieved an AUC of 0.679. Adding uric acid, albumin, and ALP increased AUC to 0.695 and slightly improved the Brier score, with good calibration. Adding the systemic immune-inflammation index did not materially improve performance. Conclusions: Routine laboratory variables provided only modest incremental value beyond OSTA. The model should be interpreted as an exploratory referral-pathway prioritization approach, not as a standalone population-screening tool. It should not be used as a diagnostic surrogate for DXA or as a fracture-risk model.