Two electrical conductivity methods of hematocrit (H) measurement, Coulter Counter (CCH) and lonometer (IH), were compared to the microhematocrit (MH) with two different anticoagulants, Li Heparin (Li) and EDTA. The results showed MH-Li is higher than MH-EDTA (mean difference 1.7 vol%). The IH-Li is 1.8 vol% higher than CC H-EDTA. These differences are attributed to osmotic shrinking of red cells by EDTA. The MH-Li and IH-Li correlate very closely (r =.992), and are considered to provide the truest hematocrit values.
©1991 American Society of Artificial Internal Organs