What is the optimal level of vitamin D in non-dialysis chronic kidney disease population?

Table 2 Baseline laboratory values, as a function of vitamin D status

	All (n = 470)	25(OH)D < 20 ng/mL (n = 252)	25(OH)D 20-29 ng/mL (n = 154)	25(OH)D ≥ 30 ng/mL (n = 64)	P
25-hydroxivitamin D (nmol/L)	52 ± 21	36 ± 9	61 ± 7	90 ± 16	< 0.001
1,25(OH)2 vitamin D (pmol/L)	103 ± 28	97 ± 27	111 ± 28	107 ± 23	< 0.001
Caalb (mmol/L)	2.40 ± 0.20	2.40 ± 0.15	2.42 ± 0.23	2.45 ± 0.23	0.163
P (mmol/L)	1.10 ± 0.26	1.10 ± 0.26	1.10 ± 0.26	1.07 ± 0.26	0.517
iPTH (ng/L)1	91 (85-97)	106 (96-116)	81 (73-91)	64 (55-74)	< 0.001
Creatinine (μmol/L)	221 ± 97	239 ± 106	212 ± 88	212 ± 88	0.017
eGFR (MDRD, mL/min per 1.73 m2)	29.4 ± 11.5	28.1 ± 11.9	30.8 ± 10.8	30.5 ± 11.1	0.049
Urine protein excretion (g/24 h)12	0.592 (0.502-0.697)	0.699 (0.573-0.853)	0.448 (0.321-0.626)	0.448 (0.271-0.742)	0.034
hsCRP (nmol/L)1	36.2 (29.5-39.1)	37.1 (33.3-41.0)	36.2 (31.4-41.0)	32.4 (26.7-39.1)	0.506
Albumin (g/L)	40 ± 5	39 ± 5	41 ± 5	40 ± 5	0.011
Total proteins (g/L)	77 ± 12	77 ± 11	77 ± 13	76 ± 14	0.877
Total cholesterol (mmol/L)	4.7 ± 1.1	4.7 ± 1.1	4.7 ± 1.0	4.8 ± 1.1	0.603
HDL cholesterol (mmol/L)	1.3 ± 0.4	1.3 ± 0.3	1.3 ± 0.4	1.3 ± 0.4	0.973
LDL cholesterol (mmol/L)	2.7 ± 0.9	2.7 ± 0.9	2.7 ± 0.9	2.9 ± 0.8	0.344
Hemoglobin (g/L)	130 ± 16	129 ± 16	132 ± 16	132 ± 18	0.058
Ferritin (pmol/L)1	225 (207-245)	227 (202-252)	216 (187-252)	247 (191-319)	0.635
Transferrin (μmol/L)	3.0 ± 1.2	2.9 ± 1.2	3.0 ± 1.2	3.1 ± 1.3	0.289
Glucose (mmol/L)	6.3 ± 2.2	6.3 ± 2.3	6.4 ± 2.4	5.9 ± 1.5	0.241

¹24 h urine proteinuria obtained in 237 (50%) patients;

²Skewed values are presented as geometric mean with 95%CI. Ca_alb: Calcium adjusted for albumin levels; eGFR: Estimated glomerular filtration rate; HSCRP: High-sensitive C reactive protein; iPTH: Intact parathyroid hormone; MDRD: Modification of diet in renal disease; P: Phosphorous; 25(OH)D: 25-hydroxivitamin D. If not indicated otherwise, results are presented as mean ± SD.