Although the frequency of samples with cell-free hemoglobin > 0.5 g/L was identical ( 17/60 vs. 17/60 ; P = 1.00 ) , the frequency of those with concentrations > 3.0 g/L was higher using BD Vacutainer One Use Holder than Holdex ( 4/60 vs. 0/60 ; P = 0.042 ) .