In this secondary analysis of consecutive ED patients with CAP from a large multicentre antibiotic stewardship trial , we used adjusted multivariate regression models to determine the magnitude and statistical significance of differences in mean baseline concentrations of five biomarkers ( procalcitonin [ PCT ] , C-reactive protein [ CRP ] , white blood cells count [ WBC ] , proadrenomedullin [ ProADM ] , copeptin ) associated with six pre-analytic factors ( antibiotic or corticosteroid pretreatment , age , gender , chronic renal failure or chronic liver insufficiency ) .