Albertine Donker

Chapter 7 234 Ranges for (untransformed) serum hepcidin concentration, stratified by age groups and sex, were constructed using the median and p25-p75. Univariable and multivariable linear regression analyses were used to evaluate the associations between (log-transformed) serum hepcidin concentrations, log-transformed hepcidin/ferritin ratio, TSAT/hepcidin ratio and selected (biochemical) variables, unadjusted and adjusted for age and time of blood sampling. The assumption of linearity between serum hepcidin concentrations and independent variables was confirmed using graphic methods. Resulting regression coefficients (ß) express the change in log-transformed serum hepcidin that are associated with a 1-unit change in the independent variable. Some of the independent variables were log-transformed as well; the interpretation of the regression coefficients for these variables is as follows: a 1% change in the independent variable corresponds to a β % change in serum hepcidin. Explained variances (R 2 ) were obtained to indicate the amount of variance in hepcidin concentration that was explained by the included variables. Analyses were stratified by sex because of sex-specific differences in hepcidin levels and iron homeostasis that have been described earlier. 20,26,27,30,38,39 SPSS version 22 was used for data analysis. Data Sharing Statement For original data, please contact dorine.swinkels@radboudumc.nl .