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

Table 1 Descriptive data for laboratory parameters at baseline, at week 2 and at week 6

Analysis	High-dose intravenous iron	Baseline, mean ± SD	Week 2, mean ± SD	Difference from baseline at week 2	Difference between FCM and FDI at week 2 (95%CI)	P value	Week 6, mean ± SD	Difference from baseline at week 6	Difference between FCM and FDI at week 6 (95%CI)	P value
Serum phosphate, mmol/L (ref. value 0.8-1.65)	FCM	1.07 ± 0.2	0.65 ± 0.2	-0.417	-0.344 (-0.427 to -0.260)	< 0.001	1.00 ± 0.3	-0.072	-0.070 (-0.144 to 0.004)	0.064
	FDI	1.15 ± 0.2	1.07 ± 0.2	-0.073			1.14 ± 0.2	-0.002
Intact FGF23, pg/mL (ref. value 11.50-48.90)	FCM	43.42 ± 14.2	91.61 ± 63.8	49.205	45.312 (25.982 to 64.697)	< 0.001	44.79 ± 23.1	1.718	1.559 (-6.407 to 9.525)	0.698
	FDI	43.88 ± 14.5	47.77 ± 22.1	3.892			44.04 ± 16.6	0.159
C-terminal FGF23, pmol/L (ref. value 0.30-3.00)	FCM	2.46 ± 3.2	1.68 ± 1.3	-0.756	6.783 (-1.319 to 14.885)	0.099	0.94 ± 1.2	-1.507	5.124 (-1.310 to 11.558)	0.116
	FDI	8.87 ± 30.6	1.33 ± 1.4	-7.539			2.24 ± 7.6	-6.632
FEPO4, % (ref. value N/A)	FCM	9.95 ± 5.8	18.70 ± 10.8	9.946	5.375 (1.801 to 8.95)	0.004	13.68 ± 11.3	4.210	3.326 (-0.309 to 6.96)	0.072
	FDI	12.55 ± 5.9	17.03 ± 8.6	4.570			13.37 ± 6.0	0.884
PTH, pmol/L (ref. value 1.5-7.0)	FCM	5.46 ± 2.6	7.02 ± 3.4	1.608	0.442 (-0.561 to 1.445)	0.384	5.97 ± 3.3	0.767	0.590 (-0.358 to 1.539)	0.220
	FDI	5.51 ± 2.6	6.72 ± 3.4	1.166			5.69 ± 2.3	0.176
Ionised calcium, mmol/L (ref. value 1.16-1.32)	FCM	1.21 ± 0.0	1.20 ± 0.0	-0.015	-0.020 (-0.035 to -0.004)	0.012	1.21 ± 0.0	0.000	-0.018 (-0.036 to -0.001)	0.044
	FDI	1.23 ± 0.0	1.23 ± 0.1	0.005			1.25 ± 0.0	0.018
25-hydroxyvitamin D, nmol/L (ref. value 50-125)	FCM	58.35 ± 24.4	57.13 ± 23.1	-1.212	-2.133 (-6.238 to 1.972)	0.305	57.48 ± 20.8	-0.865	-0.160 (-7.078 to 6.759)	0.964
	FDI	63.51 ± 21.9	64.63 ± 20.0	0.922			62.75 ± 21.1	-0.706
1,25-dihydroxyvitamin D, ng/L (ref. value 20-79)	FCM	51.10 ± 19.2	28.77 ± 17.9	-21.074	-16.463 (-24.487 to -8.438)	< 0.001	53.78 ± 20.2	3.218	5.357 (-3.164 to 13.878)	0.215
	FDI	52.85 ± 20.4	48.24 ± 17.7	-4.611			50.71 ± 19.8	-2.139

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. CI: Confidence interval; FCM: Ferric carboxymaltose; FDI: Ferric derisomaltose; FEPO4: Fractional excretion of phosphate; FGF23: Fibroblast growth factor 23; PTH: Parathyroid hormone; N/A: Not applicable.