Association of Calcium and Phosphate Levels with Incident Chronic Kidney Disease in Patients with Hypoparathyroidism: A Retrospective Case-Control Study

Table 4

Sensitivity analysis multivariable regression models of time-weighted albumin-corrected serum calcium, serum phosphate, and calcium-phosphate product and development of CKD.

Time-weighted mean level		Patients with CKD, n	Control patients without CKD, n	Odds Ratio	95% CI	value
Tertiles of albumin-corrected serum calcium, ^† (n = 150 for patients and controls)
mmol/L	mg/dL
≤2.07	≤8.28	50	50	1.11	0.62–1.97	0.73
2.08–2.19	8.32–8.76	46	54	1.00	(Reference)	—
≥2.20	≥8.80	54	46	1.47	0.82–2.66	0.20
Tertiles of serum phosphate, ^‡§ (n = 40 for patients and controls)
mmol/L	mg/dL
≤1.31	≤4.06	12	15	1.00	(Reference)	—
1.32–1.47	4.09–4.56	14	12	2.09	0.57–7.60	0.26
≥1.48	≥4.59	14	13	2.47	0.50–12.12	0.27
Tertiles of calcium-phosphate product, ^‡|| (n = 40 for patients and controls)
mmol^2/L^2	mg^2/dL^2
≤2.75	≤34.08	11	16	1.00	(Reference)	—
2.76–3.15	34.20–39.03	15	11	3.18	0.85–11.95	0.09
≥3.16	≥39.16	14	13	3.53	0.71–17.49	0.12

CCI: Charlson comorbidity index; CI: confidence interval; CKD: chronic kidney disease. Models were adjusted for the following baseline characteristics: age (continuous variable), index year (continuous variable), race (White vs Black, Asian, multi, other, or unknown), hypertension, type 2 diabetes, any acute hypoparathyroidism events, and CCI (continuous variable). ^†The target range for albumin-corrected serum calcium in patients with chronic hypoparathyroidism is defined as 2.00–2.25 mmol/L (8.0–9.0 mg/dL), which is different from the normal population reference range (2.15–2.55 mmol/L; 8.6–10.2 mg/dL). ^‡Models were adjusted for the following baseline characteristics: age (continuous variable), index year (continuous), serum phosphate level in mmol/L (baseline measurement closest to the index date, scaled 0.1-unit increase), hypocalcemia, and type 2 diabetes. ^§The reference range for serum phosphate in patients with chronic hypoparathyroidism is 0.81–1.45 mmol/L (2.5–4.5 mg/dL), which does not differ from the normal population reference range. ^||The reference range for calcium-phosphate product in patients with chronic hypoparathyroidism is ≤ 4.40 mmol²/L² (≤55 mg²/dL²), which does not differ from the normal population reference range.