Claim In autoimmune or glucocorticoid-exposed patients with advanced CKD who receive denosumab, a model that includes pre-dose parathyroid hormone (PTH), vitamin D status, and CKD-mineral bone disorder context will predict severe post-dose hypocalcemia better than corrected calcium alone.

Why this may be true Corrected calcium is only a surface signal. In CKD, denosumab abruptly suppresses osteoclast-mediated calcium efflux from bone, while impaired calcitriol production, secondary hyperparathyroidism, and altered bone turnover limit compensatory buffering. A patient can therefore have a normal or low-normal corrected calcium immediately before dosing and still be biologically primed for a major post-dose calcium drop.

Testable design

• Prospective multicenter cohort of autoimmune, glucocorticoid-treated, or osteoporosis patients with eGFR <30 mL/min/1.73 m² or dialysis receiving denosumab.
• Baseline variables: corrected calcium, ionized calcium when available, PTH, 25-OH vitamin D, phosphate, magnesium, alkaline phosphatase or bone-turnover markers, supplementation status, dialysis status, loop diuretic use.
• Primary endpoint: severe hypocalcemia within 30 days (for example corrected calcium <7.5 mg/dL, symptomatic hypocalcemia, QT prolongation, emergency visit, or admission).
• Compare discrimination/calibration of: (1) corrected-calcium-alone model, (2) corrected calcium + CKD stage, (3) full mineral-context model including PTH and vitamin D status.
• Prespecified metrics: AUROC, calibration slope, Brier score, decision-curve analysis.

Falsification The hypothesis fails if corrected calcium alone performs equivalently to the fuller mineral-context model after internal-external validation.

Limitations PTH assays vary across sites; bone-turnover markers may be missing; confounding by indication and supplementation rescue protocols must be modeled explicitly.

References

1. Block GA, Bone HG, Fang L, Lee E, Padhi D. J Bone Miner Res. 2012;27(7):1471-1479. DOI: 10.1002/jbmr.1613
2. Dave V, Chiang CY, Booth J, Mount PF. Am J Nephrol. 2015;41(2):129-137. DOI: 10.1159/000380960
3. Kwon YE, Lee JH, Kim YL, et al. Clin Kidney J. 2024;17(1):sfad241. DOI: 10.1093/ckj/sfad241