Hypophosphatemia after high-dose intravenous iron treatment in patients with inflammatory bowel disease: Mechanisms and possible clinical impact

Table 2 Laboratory parameters for patients stratified by hypophosphatemia status (with/without) at week 2 and at week 6

Analysis	High-dose intravenous iron	Week 2 serum phosphate ≥ 0.8 mmol/L, mean ± SD	Week 2 serum phosphate < 0.8 mmol/L, mean ± SD	Difference	P value	Week 6 serum phosphate ≥ 0.8 mmol/L, mean ± SD	Week 6 serum phosphate < 0.8 mmol/L, mean ± SD	Difference	P value
Intact FGF23, pg/mL (ref. value 11.50-48.90)	FCM	33.71 ± 10.56 (n = 14/51)	114.33 ± 62.22 (n = 37/51)	80.62	< 0.001	39.30 ± 16.79) (n = 40/51)	66.86 ± 30.05 (n = 11/51)	27.56	0.013
	FDI	45.82 ± 16.90 (n = 47/53)	57.16 ± 46.35 (n = 6/53)	11.43	0.577	43.85 ± 16.83 (n = 52/54)	48.93 ± 10.13 (n = 2/54)	5.08	0.604
C-terminal FGF23, pmol/L (ref. value 0.30-3.00)	FCM	1.03 ± 0.99 (n = 14/51)	1.93 ± 1.33 (n = 37/51)	0.9	0.014	0.76 ± 0.63 (n = 40/51)	1.64 ± 2.14 (n = 11/51)	0.88	0.206
	FDI	1.36 ± 1.47 (n = 47/53)	1.08 ± 0.72 (n = 6/53)	-0.28	0.465	2.27 ± 7.79 (n = 52/54)	1.31 ± 0.33 (n = 2/54)	-0.97	0.384
FEPO4, % (ref. value N/A)	FCM	13.35 ± 5.94 (n = 12/46)	20.59 ± 11.60 (n = 34/46)	7.24	0.009	9.62 ± 6.56 (n = 36/47)	26.99 ± 13.38 (n = 11/47)	17.37	0.001
	FDI	15.97 ± 7.85 (n = 46/52)	25.11 ± 10.22 (n = 6/52)	9.14	0.080	13.00 ± 5.79 (n = 52/54)	22.85 ± 4.41 (n = 2/54)	9.85	0.176
PTH, pmol/L (ref. value 1.5-7.0)	FCM	5.46 ± 2.83 (n = 14/48)	7.46 ± 3.23 (n = 34/48)	2	0.042	5.22 ± 2.39 (n = 39/47)	9.93 ± 4.43) (n = 8/47)	4.71	0.020
	FDI	6.28 ± 2.97 (n = 47/53)	10.13 ± 4.70 (n = 6/53)	3.85	0.102	5.66 ± 2.32 (n = 52/54)	6.40 ± 1.70 (n = 2/54)	0.74	0.649
Ionised calcium, mmol/L (ref. value 1.16-1.32)	FCM	1.21 ± 0.32 (n = 13/50)	1.19 ± 0.05 (n = 37/50)	-0.02	0.336	1.21 ± 0.05 (n = 40/51)	1.22 ± 0.04 (n = 11/51)	0.01	0.496
	FDI	1.24 ± 0.45 (n = 46/52)	1.21 ± 0.09 (n = 6/52)	-0.03	0.422	1.25 ± 0.05 (n = 51/53)	1.23 ± 0.02 (n = 2/53)	-0.02	0.314
25-hydroxyvitamin D, nmol/L (ref. value 50-125)	FCM	63.00 ± 30.94 (n = 14/51)	54.54 ± 19.69 (n = 37/51)	-8.46	0.354	60.05 ± 21.68 (n = 40/51)	45.45 ± 10.00 (n = 11/51)	-14.6	0.002
	FDI	64.16 ± 20.30 (n = 45/51)	64.83 ± 18.93 (n = 6/51)	0.67	0.937	63.68 ± 20.97 (n = 50/52)	39.50 ± 2.12 (n = 2/52)	-24.18	< 0.001
1,25-dihydroxyvitamin D, ng/L (ref. value 20-79)	FCM	46.34 ± 19.10 (n = 14/50)	21.46 ± 11.63 (n = 36/50)	-24.88	< 0.001	56.76 ± 20.27 (n = 40/50)	40.89 ± 15.95 (n = 10/50)	-15.87	0.016
	FDI	49.05 ± 18.52 (n = 47/53)	45.72 ± 7.15 (n = 6/53)	-3.33	0.414	50.88 ± 19.92 (n = 52/54)	46.45 ± 21.85 (n = 2/54)	-4.43	0.822

Normal phosphate levels: > 0.8 mmol/L = > 2.48 mg/dL; Mild hypophosphatemia 0.79-0.6 mmol/L = 2.44-1.86 mg/dL; Moderate hypophosphatemia 0.59-0.32 mmol/L = 1.83-0.99 mg/dL; Severe hypophosphatemia < 0.32 mmol/L = < 0.99 mg/dL. FCM: Ferric carboxymaltose; FDI: Ferric derisomaltose; FEPO4: Fractional excretion of phosphate; FGF23: Fibroblast growth factor 23; PTH: Parathyroid hormone; N/A: Not applicable.