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

Table 1

Demographic, clinical characteristics, and biochemical parameter levels at the baseline in patients with chronic hypoparathyroidism and CKD and matched patient controls.

Parameter	Albumin-corrected serum calcium cohort (n = 300)			Phosphate and calcium-phosphate cohort (n = 80)
	Patients with CKD (n = 150)	Control patients without CKD (n = 150)	value	Patients with CKD (n = 40)	Control patients without CKD (n = 40)	value
Demographics
Age at index date^†‡ (years), mean ± SD	57.7 ± 12.8	57.8 ± 12.8	0.78	57.2 ± 12.4	57.6 ± 12.8	0.28
Female, n (%)	125 (83.3)	125 (83.3)	—	33 (82.5)	33 (82.5)	—
Race, ^†n (%)
White	125 (83.3)	129 (86.0)	0.61	33 (82.5)	32 (80.0)	1.00
Black	18 (12.0)	5 (3.3)	<0.01^¶	6 (15.0)	4 (10.0)	0.68
Asian, multi, other, unknown	7 (4.7)	16 (10.7)	0.10	1 (2.5)	4 (10.0)	0.37
Average exposure window duration (years), mean ± SD	2.8 ± 2.2	2.8 ± 2.2	—	2.5 ± 2.3	2.5 ± 2.3	—
Clinical characteristics
Comorbidities during baseline
CCI score, ^†mean ± SD	1.3 ± 2.3	1.6 ± 2.4	0.23	1.8 ± 3.0	1.7 ± 2.1	0.83
Type 2 diabetes, ^†‡n (%)	20 (13.3)	16 (10.7)	0.56	2 (5.0)	5 (12.5)	0.45
Hypertension, ^†n (%)	46 (30.7)	49 (32.7)	0.79	9 (22.5)	11 (27.5)	0.81
Any acute HypoPT events during baseline, ^†§n (%)	60 (40.0)	56 (37.3)	0.71	21 (52.5)	21 (52.5)	1.00
Hypocalcemia, ^†‡n (%)	43 (28.7)	38 (25.3)	0.58	16 (40)	19 (47.5)	0.66
Biochemical parameters, ^||mean ± SD
Albumin-corrected total serum calcium, mmol/L	2.0 ± 0.3	2.1 ± 0.3	0.82	1.9 ± 0.4	2.1 ± 0.3	0.19
Serum phosphate, ^‡mmol/L	1.5 ± 0.4	1.5 ± 0.4	0.83	1.4 ± 0.4	1.4 ± 0.4	0.72
Calcium-phosphate product, mmol^2/L^2	2.8 ± 1.1	3.0 ± 0.9	0.46	2.9 ± 1.1	2.8 ± 0.8	0.70
eGFR, mL/min/1.73 m^2	86 ± 14.0	91 ± 14.8	0.18	91 ± 12.4	87 ± 13.1	0.40

CCI: Charlson comorbidity index; CKD: chronic kidney disease; eGFR: estimated glomerular filtration rate; HypoPT: hypoparathyroidism. Index date was the day after the first calcitriol prescription. ^†Albumin-corrected serum calcium regression models were adjusted for this parameter. ^‡Serum phosphate and calcium-phosphate product regression models were adjusted for this parameter.^§“Any acute HypoPT event” included hypercalcemia, hypocalcemia, laryngeal spasm, muscle spasm, other convulsions, tetanic cataract, tetany, cardiac dysrhythmias, palpitations, and tachycardia. ^||Value closest to the index date. ^¶Denotes value < 0.05.