Table 5.

Multilevel regression analysis of the log-transformed ratio between potassium intake excretion in men from 13 European centers from the EPIC and EFCOVAL studies

Modela	Model i	Model ii
	Random intercept for center—no explanatory variables	Random intercept for center—explanatory variables at the individual level
N	799	799
Likelihood ratio	715	706
Likelihood ratio testb		p = 0.002
\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \sigma_{u0}^{2} $$\end{document}—Center random effect ± SE (p value)	0.008 ± 0.004 (0.03)	0.009 ± 0.005 (0.02)
CV (%, relative to reference method)	8.9%	9.5%
\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \sigma_{e0}^{2} $$\end{document}—Within center random effect ± SE (p value)	0.139 ± 0.007 (<0.001)	0.138 ± 0.006 (<0.001)
VPC—Variance partition coefficient	0.05	0.06
Individual variables—effect (p values)	–	BMI −0.01 (0.002)
Proportion of between-center variance explainedb	–	0%
Centers with bias deviating from the mean log-transformed ratio	Nice (FR), Heidelberg (GE), Greece (GR), Northern Italy (IT)	Nice (FR), Heidelberg (GE), Greece (GR), Northern Italy (IT)

^aFit of model iii was not significantly better than the previous one. Therefore, results are not presented

^bCompared to the previous fitted model