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

Table 3

Association between serum phosphate and calcium-phosphate product and development of CKD.

	Patients with CKD (n = 40), n	Control patients without CKD (n = 40), n	Matched groups			Adjusted analyses
			Odds Ratio	95% CI	value	Odds Ratio	95% CI	value
Any serum phosphate measurements above 0.81–1.45 mmol/L (2.5–4.5 mg/dL)^†
Yes	26	25	0.97	0.34–2.73	0.95	0.95	0.32–2.86	0.93
No	14	15	1.00	(Reference)	—	1.00	(Reference)	—
Any calcium-phosphate product measurements above 4.40 mmol^2 /L^2 (>55 mg^2 /dL^2)^‡
Yes	5	4	1.07	0.26–4.39	0.93	0.79	0.16–4.01	0.78
No	35	36	1.00	(Reference)	—	1.00	(Reference)	—

CI: confidence interval; CKD: chronic kidney disease. Matching for groups was 1:1 based on age ± 5 years, sex, index date ± 1 year, and exposure window duration. Adjusted models were adjusted for the following baseline characteristics: age (continuous variable), index year (continuous), serum phosphate level in mmol/L (baseline measurement closest to 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.