Plasma markers of intravascular hemolysisBefore RBC transfusion, plasma heme levels were comparablebetween both groups (0.16 [0.14; 0.18] vs. 0.17[0.13; 0.25] OD; p = 0.60), and concentrations did notchange after transfusion. At baseline, haptoglobin levelwas lower in the worsening group (0.6 [0.2; 1] vs. 1.7[1.1; 2.1] g/L; p = 0.007) and after transfusion, haptoglobinconcentration slightly decreased in both groups, butremained detectable for all patients. Finally, anotherintravascular hemolysis marker, carboxyhemoglobin(HbCO) level, was comparable between both groups beforetransfusion (1.5 [1.3; 2] vs. 1.4 [1.3; 2]%; p = 0.65)and did not change after RBC transfusion (Fig. 2).