Table 5.

Modifying factors of phosphate concentration stratified by sex at 12 months of age

Variable	β	B	t	P value
Boys
Iron, µmol/L	0.143	0.004	2.142	0.033
Intact FGF23 (pg/mL)	0.157	0.073	2.352	0.020
25OHD (nmol/L)	-0.149	-0.001	-2.272	0.024
Calcium in food (mg/kcal)	0.134	0.062	2.018	0.045
Girls
Iron, µmol/L	0.244	0.007	3.790	<0.001
Season (1 = winter, 2 = others)	-0.170	-0.064	-2.644	0.009

The following variables were included in the regression model: season, PTH,^a 25OHD, ionized calcium, alkaline phosphatase,^a iron, creatinine, dietary intake variables (phosphate, calcium, vitamin D), length, weight, intact FGF23,^a and C-terminal FGF23.^a Model (boys): R² 0.091, adjusted R² 0.074, significant F change 0.045, Durbin-Watson 2.136. Model (girls): R² 0.091, adjusted R² 0.082, significant F change 0.009, Durbin-Watson 2.030. Analysis performed using linear regression model with forward method. The table includes all variables with statistical significance below 0.05 (P < 0.05).

Abbreviations: 25OHD, serum 25-hydroxyvitamin D; β, standardized regression coefficient; B, regression coefficient; FGF23, fibroblast growth factor 23; t, t-statistic.

^a After logarithmic transformation.