Table 4.

Age-specific reference ranges of the main parameters of phosphate/calcium metabolism in term infants, adapted from [9, 44, 45]

	iCa mmol/L	Ca mg/dL	Ca mmol/L	P mg/dL	P mmol/L	ALP IU/L	Albumin g/L	Creatinine mg/dL	Creatinine µmol/L	PTH	25 OH-D nmol/L	25OH-D ng/mL
0–14 days	1.22–1.40	8.5–11.0	2.13–2.75	5.6–10.5	1.81–3.39	90–273	33–45	0.32–0.92	28–81	No assessment before 4 weeks of life	75–120	30–48
15–30 days	1.22–1.40	8.5–11.0	2.13–2.75	4.8–8.4	1.55–2.71	134–518	28–47	0.10–0.36	9–32	No assessment before 4 weeks of life	75–120	30–48
30 days to 6 months	1.22–1.40	8.5–11.0	2.13–2.75	4.8–8.4	1.55–2.71	134–518	28–47	0.10–0.36	9–32	Mild CKD: normal levels Moderate CKD: 1–2 ULN Advanced CKD/dialysis: 2–3 ULN	75–120	30–48
6 months to 1 year	1.20–1.40	8.5–11.0	2.13–2.75	4.8–8.4	1.55–2.71	134–518	28–47	0.10–0.36	9–32	Mild CKD: normal levels Moderate CKD: 1–2 ULN Advanced CKD/dialysis: 2–3 ULN	75–120	30–48
1 to 2 years	1.22–1.32	9.2–10.5	2.30–2.63	4.3–6.8	1.39–2.20	156–369	38–47	0.10–0.36	9–32	Mild CKD: normal levels Moderate CKD: 1–2 ULN Advanced CKD/dialysis: 2–3 ULN	75–120	30–48

Results are presented as lower and upper limit. For calcium, the conversion factor from mg/dL to mmol/L is to divide by 4.0. The calculation formula for corrected calcium (CaC, mmol/L) using measured calcium (mmol/L) and serum albumin (g/L) is the following: CaC = Ca − 0.25 × (serum albumin − 40). If serum albumin is not available, CaC may be calculated with protidemia (g/L) with the following formula: CaC = Ca/(0.55 + P/16). For phosphate, the conversion factor from mg/dL to mmol/L is to divide by 3.1. For creatinine, the conversion factor from mg/dL to µmol/L is to multiply by 88.4. In the CALIPER database, albumin was assessed with bromocresol green and creatinine with an enzymatic assay. ULN, upper limit normal for the local assay