Albertine Donker

Chapter 7 244 Table 5. Results of linear regression models for hepcidin/ferritin ratio (pmol/µg) adjusted for age and time of blood sampling and stratified by sex Males 95% CI Variable Beta a Lower limit Upper limit R 2 , % b p Hb, g/dL -0.007 -0.098 0.084 26.3 0.885 Reticulocytes, x10^9/L 0.000 -0.005 0.005 26.3 0.927 MCV, fL -0.007 -0.029 0.015 26.5 0.515 Iron, µmol/L 0.009 -0.005 0.023 26.0 0.216 TIBC, µmol/L -0.003 -0.012 0.005 26.5 0.469 TSAT, % 0.006 -0.002 0.014 26.2 0.165 sTfR, mg/L -0.119 -0.408 0.170 26.3 0.417 ALT, IU/L d 0.162 -0.321 0.645 26.5 0.508 CRP, mg/L d,e 0.134 0.023 0.244 29.0 0.018 BMI f Normal weight ref ref ref Underweight 0.610 0.112 1.108 29.0 0.017 Overweight 0.169 -0.045 0.383 0.121 Adipose 0.019 -0.370 0.409 0.922 Adjustment for age was done with age as a continuous variable; adjustment for sampling time was done with sampling time as a categorical variable (7.30 AM-12 PM, 12-3 PM, 3-6 PM). a Beta expresses the change in the dependent variable -log-transformed serum hepcidin/ferritin ratio- that is associated with a 1-unit change in the independent variable. Independent variables marked with d were log-transformed as well; the interpretation of the regression coefficients for these variables are as follows: a 1% change in the independent variable corresponds to a beta % change in hepcidin/ferritin ratio b For males multivariate linear regression model with log-transformed hepcidin/ferritin ratio as dependent variable and age (continuous variable) and sampling time as independent variables showed: R 2 26.8%, with ß -0.057, CI -0.072- -0.041 ( p 0.000), ß 0.175, CI 0.023-0.326 ( p 0.024), ß 0.432, CI 0.221-0.643 ( p 0.000)\