Table 3.

Multiple regression analysis between log-FGF23 level versus serum calcium, phosphorus, PTH and 25(OH)vitamin D at Months 1, 6 and 12 of follow-up

Dependent variable	Independent variables	Regression coefficient	SEM	t-test value H0≠0	P value	IC 95% lower limit	IC 95% upper limit
Log FGF23 Month 1	Intercept	−2.259	1.003	−2.251	0.033	−4.325	−0.192
	Calcium	0.372	0.093	3.996	0.001	0.180	0.564
	Phosphorus	−0.021	0.099	−0.210	0.835	−0.225	0.183
	Parathyroid Hormone	0.001	0.000	1.290	0.209	0.000	0.001
	25 (OH) D	0.015	0.014	1.100	0.282	−0.013	0.044
Log FGF23 Month 6	Intercept	−6.476	3.309	−1.957	0.086	−14.105	1.154
	Calcium	0.884	0.340	2.603	0.031	0.101	1.667
	Phosphorus	−0.132	0.162	−0.817	0.438	−0.506	0.241
	Parathyroid Hormone	0.001	0.001	1.808	0.108	0.000	0.003
	25 (OH)vit D	−0.005	0.027	−0.189	0.855	−0.068	0.057
Log FGF23 Month 12	Intercept	−5.257	1.504	−3.495	0.005	−8.567	−1.946
	Calcium	0.566	0.161	3.514	0.005	0.212	0.921
	Phosphorus	0.322	0.101	3.194	0.009	0.100	0.544
	Parathyroid Hormone	−0.001	0.001	−1.457	0.173	−0.002	0.001
	25 (OH)vit D	0.005	0.017	0.295	0.774	−0.032	0.042

Calcemia was found to be the strongest variable determining FGF23 plasma levels during the observation period. At Month 12, phosphemia showed a statistical significance, however, it was lost when serum calcium was removed from the model.