Table 4.

Subgroup analysis for square root of serum hepcidin level according to CKD stages in multivariable linear regression analysis.

	CKD stage 1–3a		CKD stage 3b–5
	Beta (95% CI)	P	Beta (95% CI)	P
Age (years)	0.002 (−0.004–0.009)	0.477	−0.003 (−0.011–0.004)	0.397
Sex (men vs. female)	0.105 (−0.124–0.335)	0.369	−0.260 (−0.519–0.000)	0.050
Ever smoking (yes vs. no)	0.075 (−0.113–0.263)	0.433	0.038 (−0.202–0.277)	0.758
SBP (mm Hg)	−0.002 (−0.007–0.003)	0.460	0.002 (−0.003–0.007)	0.381
Glucose (mmol/l)	−0.010 (−0.051–0.031)	0.641	−0.013 (−0.049–0.023)	0.466
eGFR (ml/min/1.73 m2)	−0.002 (−0.005–0.001)	0.279	−0.025 (−0.035–−0.015)	<0.001
Albumin (g/l)	0.049 (0.026–0.072)	<0.001	0.025 (0.001–0.050)	0.045
Cholesterol (mmol/l)	0.023 (−0.056–0.103)	0.569	−0.075 (−0.160–0.010)	0.085
WBC (×103/μl)	0.033 (−0.009–0.076)	0.125	0.049 (0.003–0.096)	0.037
CRP (nmol/l)	0.079 (0.021–0.136)	0.008	0.119 (0.055–0.182)	<0.001
UPCR (g/g)	−0.009 (−0.066–0.047)	0.745	0.019 (−0.059–0.097)	0.632
Hemoglobin (g/dl)	−0.165 (−0.221–−0.109)	<0.001	−0.187 (−0.250–−0.124)	<0.001
Ferritin (pmol/l)	0.939 (0.847–1.031)	<0.001	1.460 (1.359–1.562)	<0.001
TSAT (%)	0.010 (0.004–0.017)	0.002	0.010 (0.002–0.019)	0.015
ESA use (yes vs. no)	−1.366 (−2.944–0.213)	0.090	0.655 (0.386–0.924)	<0.001
Iron supplements (yes vs. no)	0.647 (0.317–0.978)	<0.001	0.125 (−0.104–0.354)	0.284
Bilirubin (μmol/l)	0.013 (−0.002–0.028)	0.093	0.017 (−0.008–0.043)	0.178

SBP, systolic blood pressure; eGFR, estimated glomerular filtration rate; WBC, white blood cells; CRP, C-reactive protein; UPCR, urine protein-to-creatinine ratio; TSAT, transferrin saturation; ESA, erythropoiesis stimulating agents.

Logarithmic transformations were done for CRP, UPCR and ferritin. Variables with P < 0.05 in univariable linear regression analysis were chosen as covariates in multivariable linear regression analysis.