Measurements of Free Hemoglobin and Hemolysis Index: EDTA- or Lithium-Heparinate Plasma?

There is no agreement as to the optimal sample type to be used for measurements of free hemoglobin (fHb) in plasma. (Because fHb is increased during clotting, serum is not recommended.) Several publications have recommended the use of EDTA as an anticoagulant (2), but another author reported 20-fold higher fHb values in EDTA-plasma than in Li-heparinate plasma and therefore recommended Li-heparinate plasma for such analyses (1). Because Li-heparinate and EDTA plasma are often used for emergency and routine measurements, we explored this issue and searched for a practicable, inexpensive, and rapid method for fHb measurements. Blood from 49 patients was collected into sample tubes (Monovette, Sarstedt) containing EDTA (1.6 g/L of whole blood) or Li-heparinate (16 kIE/L of whole blood). Samples were collected from patients who required laboratory analyses. Patients gave informed consent, and the study received institutional review …