Association between glomerular filtration rate and 1,25-dihydroxyvitamin D in cardiac surgery

Figures & data

Table I. Biochemical characteristics and eGFR values of the study groups.

Parameter	Reference laboratory value	Surgical patients (n = 59)		HTx-patients (n = 151)		P-value
		t1	t2	t1	t2	Time	Group	Time × Group interaction
Calcium (mmol/l)	2.1 – 2.75	2.10 ± 0.13	2.23 ± 1.30	2.14 ± 0.18	2.10 ± 0.32	0.067	0.070	<0.001
Magnesium (mmol/l)	0.45 – 0.99	0.86 ± 0.11	0.88 ± 0.10	0.76 ± 0.12	0.63 ± 0.14	<0.001	<0.001	<0.001
PTH (pg/ml)	10 – 72	55.4 ± 50.1	59.5 ± 58.5	86.2 ± 76.8	79.0 ± 70.0	0.206	<0.001	0.170
25(OH)D (nmol/l)	50 – 125	44.9 ± 38.7	39.5 ± 9.1	22.1 ± 12.6	19.6 ± 14.7	0.001	<0.001	0.096
1,25(OH)2D (pmol/l)	41 – 127	63.9 ± 49.0	56.3 ± 36.9	25.2 ± 21.2	35.4 ± 18.9	0.386	<0.001	<0.001
C-reactive protein (mg/dl)	<0.8	10.3 ± 6.01	2.44 ± 3.71	4.67 ± 5.24	2.41 ± 3.51	<0.001	<0.001	<0.001
Creatinine (mg/dl)	0.6–1.2	0.94 ± 0.34	1.01 ± 0.34	1.94 ± 0.85	1.63 ± 0.71	0.034	<0.001	<0.001
Cystatin-C (mg/dl)	0.64 – 1.04	1.06 ± 0.31	1.18 ± 0.42	2.72 ± 1.14	2.20 ± 1.07	0.007	<0.001	<0.001
SCr-eGFR (ml/min/1.73m^2)	>90	88.7 ± 25.9	80.6 ± 21.7	45.9 ± 26.0	53.4 ± 25.4	0.352	<0.001	<0.001
CysC-eGFR (ml/min/1.73m^2)	>90	71.8 ± 21.0	64.8 ± 21.2	25.0 ± 13.8	34.0 ± 18.4	0.923	<0.001	<0.001

HTx, heart transplantation, PTH, parathyroid hormone; 25(OH)D, 25-Hydroxyvitamin D; 1,25(OH)₂D, 1,25-Dihydroxyvitamin D; SCr, serum creatinine; CysC, cystatin; eGFR, estimated glomerular filtration rate.

Figure 1. Bland-Altman plots showing the bias between the SCr-eGFR and the mean of the two eGFR methods at t1 (A), t2 (B), t3 (C) and t0 (D); Figure 1C is restricted to heart transplant recipients only and Figure 1D is restricted to other cardiac surgical patients only; the lines indicate the mean +/2 2 standard deviations. CysC, cystatin C; SCr, serum creatinine; eGFR, estimated glomerular filtration rate.

Table II. Correlation coefficients of 1,25(OH)₂D with CysC-eGFR and SCr-eGFR in the two study groups at different time points.

Parameter	HTx patients (n = 151) 1,25(OH)2D		Other cardiac surgical patients (n = 59) 1,25(OH)2D
	t1	t2	t0	t1	t2
CysC-eGFR	0.253**	0.443***	0.188	0.405***	0.459***
SCr-eGFR	0.139	0.196*	0.182	0.287*	0.195

HTx, heart transplantation, 1,25(OH)₂D, 1,25-Dihydroxyvitamin D; SCr, serum creatinine; CysC, cystatin; eGFR, estimated glomerular filtration rate.

*p<0.05;**p<0.01; ***p<0.001.

Figure 2. Correlation between circulating 1,25-dihydroxyvitamin D and serum creatinine-based (A) and cystatin C-based (B) estimates of glomerular filtration rate. CysC, cystatin C; SCr, serum creatinine; eGFR, estimated glomerular filtration rate.