Concentrations of potassium ( 4.25 vs. 4.16 mmol/L ; P = 0.031 ) , LD ( 498 vs. 459 U/L ; P = 0.039 ) and cell-free hemoglobin ( 0.42 vs. 0.22 g/L ; P = 0.042 ) were higher in samples collected with BD Vacutainer One Use Holder than with Holdex .