A Simple-to-Use Score for Identifying Individuals at High Risk of Denosumab-Associated Hypocalcemia in Postmenopausal Osteoporosis: A Real-World Cohort Study

Since denosumab-associated hypocalcemia occurs infrequently, data on its incidence and risk factors are limited. We aimed to evaluate risk factors and develop a useful score for identifying individuals at risk of denosumab-associated hypocalcemia. In this retrospective cohort, 790 consecutive female patients who received 60 mg denosumab at least once between 2016 and 2017 were analyzed. Based on biochemical records from a large-scale single-center, mild and moderate hypocalcemia were defined as albumin-corrected calcium (cCa) levels < 8.5 and < 8.0 mg/dL (< 2.12 and < 2.0 mmol/L), respectively. Mild and moderate hypocalcemia were observed in 8.2% and 1.0% patients, respectively. Patients who developed mild hypocalcemia had lower baseline cCa (8.9 vs. 9.3 mg/dL and 2.22 vs. 2.32mmo/L) and estimated glomerular filtration rate (75.0 vs. 83.2 mL/min/1.73 m2) and more frequent loop diuretic use (10.8% vs. 4.4%; all p < 0.05). In multivariate analysis, low baseline cCa (OR 1.29; 95% CI 1.20–1.40) and chronic kidney disease (CKD) stages 3b-5 were associated with elevated mild hypocalcemia risk (OR 2.92; 95% CI 1.38–6.20). Loop diuretics use was associated with mild hypocalcemia (OR 2.61; 95% CI 1.11–6.18) by univariate analysis, independent of baseline cCa and CKD stage. A scoring approach identified two risk groups: (1) patients without CKD (eGFR ≥ 45) and cCa < 8.5 mg/dL (2.12 mmol/L) and (2) patients with CKD (eGFR < 45) and cCa < 9.5 mg/dL (2.37 mmol/L).