Table 4.
Influence of cFGF23 and iFGF23 on biomarkers of iron metabolism, EPO concentrations and inflammation biomarkers.
| Independent Variable | ||||||
|---|---|---|---|---|---|---|
| * cFGF23 (RU/mL) | ** iFGF23 (pg/mL) | |||||
| Dependent Variable | exp(Beta) | p | R2 | exp(Beta) | p | R2 |
| TSAT (%) | 0.89 (0.85/0.94) | <0.001 | 0.17 | 0.95 (0.68/1.31) | 0.744 | 0.06 |
| Serum iron (µg/dl) | 0.92 (0.88/0.96) | <0.001 | 0.25 | 1.04 (0.78/1.39) | 0.802 | 0.18 |
| Ferritin (µg/L) | 0.89 (0.81/0.99) | 0.032 | 0.20 | 1.09 (0.56/2.14) | 0.795 | 0.17 |
| Hepcidin (pg/mL) | 0.73 (0.63/0.85) | <0.001 | 0.22 | 0.72 (0.26/1.97) | 0.519 | 0.15 |
| EPO (mU/mL) | 1.17 (1.08/1.27) | <0.001 | 0.11 | 1.57 (0.93/2.66) | 0.09 | 0.05 |
| CRP (mg/dl) | 1.01 (0.88/1.16) | 0.863 | 0.17 | 0.63 (0.27/1.49) | 0.291 | 0.18 |
| IL 6 (pg/mL) | 1.11 (1.01/1.22) | 0.029 | 0.32 | 1.19 (0.64/2.23) | 0.575 | 0.31 |
Back-transformed regression coefficients (exp(Beta)) and confidence intervals for the dependent variables are indicated in the line headings. The respective independent variable (marker) is indicated by column heading (cFGF23, iFGF23, phosphate, total calcium). Regression models were adjusted for albumin, gender, eGFR, and presence of Diabetes mellitus type II (Base model). Independent variables: * indicates that calculations were performed with binary-log-transformed independent variables such that Beta quantifies the effect of doubling the independent variable (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. Dependent variables: all of the dependent variables have been binary-log transformed and subsequently estimates back-transformed, such that the given coefficient (exp(Beta)) quantifies a multiplicative effect of the independent variable (column heading) on the dependent variable (line heading); e.g., effect of cFGF23 on TSAT: doubling cFGF23 translates into an average reduction of TSAT by 11% (0.89xTSAT); effect of calcium on TSAT: one unit increase in calcium translates into a non-significant average reduction of TSAT by 20% (0.80xTSAT). cFGF23: c-terminal Fibroblast Growth Factor 23; iFGF23: intact Fibroblast Growth Factor 23; TSAT: transferrin saturation; EPO: erythropoietin; CRP: C-reactive protein; IL-6: Interleukin 6; eGFR: estimated glomerular filtration rate (CKD-EPI formula).