Table 2.
Dependence of hemoglobin on biomarkers of mineral metabolism, iron metabolism, EPO concentrations, and inflammation biomarkers.
| Dependent Variable | ||||||
|---|---|---|---|---|---|---|
| Hemoglobin (g/dL) | ||||||
| Unadjusted | Adjusted Base Model | |||||
| Biomarker | Beta | p | R2 | Beta | p | R2 |
| cFGF23 (RU/mL) * | −0.65 (−0.78/−0.51) | <0.001 | 0.29 | −0.28 (−0.44/−0.11) | 0.001 | 0.49 |
| iFGF23 (pg/mL) ** | −3.26 (−4.01/−2.51) | <0.001 | 0.25 | −1.04 (−2.1/0.03) | 0.057 | 0.45 |
| Klotho (pg/mL) * | 1.04 (0.39/1.69) | 0.002 | 0.07 | 0.30 (−0.26/0.87) | 0.289 | 0.43 |
| Total calcium (mmol/L) | 4.35 (3.09/5.6) | <0.001 | 0.17 | 2.15 (0.91/3.39) | <0.001 | 0.48 |
| Alb-corr calcium (mmol/L) | 3.21 (1.67/4.75) | <0.001 | 0.07 | |||
| Phosphate (mmol/L) * | −2.48 (−3.11/−1.84) | <0.001 | 0.21 | −0.75 (−1.42/−0.07) | 0.032 | 0.46 |
| PTH (pg/mL) * | −0.65 (−0.83/−0.46) | <0.001 | 0.18 | −0.14 (−0.36/0.07) | 0.191 | 0.46 |
| 25(OH) (nmol/L) * | 0.46 (0.16/0.75) | 0.003 | 0.04 | 0.06 (−0.19/0.30) | 0.658 | 0.45 |
| 1,25(OH)2D (pmol/L) * | 0.89 (0.59/1.19) | <0.001 | 0.14 | 0.02 (−0.29/0.32) | 0.911 | 0.45 |
| Serum iron (µg/dl) * | 1.41 (0.96/1.85) | <0.001 | 0.18 | 0.74 (0.33/1.16) | <0.001 | 0.46 |
| Ferritin (µg/L) * | 0.09 (−0.1/0.28) | 0.37 | 0 | 0.07 (−0.09/0.22) | 0.404 | 0.45 |
| Transferrin (mg/dl) | 0.01 (0/0.02) | 0.004 | 0.05 | 0 (−0.01/0.01) | 0.905 | 0.42 |
| TSAT (%) * | 0.96 (0.51/1.41) | <0.001 | 0.09 | 0.56 (0.18/0.94) | 0.004 | 0.45 |
| sTFR (mg/L) * | 0.31 (−0.3/0.92) | 0.321 | 0.01 | 0.47 (0/0.95) | 0.052 | 0.43 |
| Hepcidin (pg/mL) * | 0.03 (-0.1/0.15) | 0.695 | 0 | 0.14 (0.04/0.24) | 0.007 | 0.47 |
| EPO (mU/mL) * | −0.53 (−0.79/−0.28) | <0.001 | 0.07 | −0.34 (−0.53/−0.15) | <0.001 | 0.48 |
| CRP (mg/dl) * | −0.16 (−0.3/−0.02) | 0.026 | 0.02 | 0.05 (−0.07/0.17) | 0.407 | 0.45 |
| IL 6 (pg/mL) * | −0.47 (−0.64/−0.29) | <0.001 | 0.12 | 0 (−0.16/0.17) | 0.961 | 0.45 |
Regression coefficients (beta) and confidence intervals with hemoglobin as dependent variable for respective markers from unadjusted linear regression models (left columns) and from regression models adjusting for albumin, gender, eGFR, and presence of Diabetes mellitus type II (adjusted base model, right columns). R2 values for the adjusted base model refer to adjustment variables plus the respective marker (adjustment variables alone achieve R2 = 0.45). * indicates that calculations were performed with binary-log-transformed marker values such that beta quantifies the effect of doubling the marker (otherwise beta quantifies the effect of one additional unit). ** indicates that calculations were performed with double log-transform, i.e., binary log of the binary log of iFGF23, such that beta quantifies the effect of squaring the value of iFGF23. PTH: parathyroid hormone; cFGF23: c-terminal Fibroblast Growth Factor 23; iFGF23: intact Fibroblast Growth Factor 23; 25(OH)D: 25 hydroxy-vitamin D3; 1,25(OH)2D: 1, 25 dihydroxy-vitamin D3; CRP: C-reactive protein; IL-6: Interleukin 6; TSAT: transferrin saturation; sTFR: soluble transferrin receptor; EPO: erythropoietin; eGFR: estimated glomerular filtration rate (CKD-EPI formula).