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Automated methods, with and without cyanide (+CN and -CN), for whole blood hemoglobin (Hb) determination were evaluated on the Technicon H*1TM System. Both automated Hb methods were linear over the range 0-250 g/L (0-25 g/dL) and correlated well with the International Committee for Standardization of Hematology (ICSH) reference method and with the Coulter S+II. Both methods quantitatively converted whole blood containing up to 100% carboxyhemoglobin in less than 24 seconds to their respective end products. With respect to abnormal samples (sickle cell anemia, multiple myeloma, and hyperlipemia), both H*1 methods gave Hb results that were equivalent to the (postfiltration) ICSH method. For samples with white blood cell (WBC) counts less than 36 X 10(9)/L, the +CN method was equivalent to the (postfiltration) ICSH method, whereas for WBC counts greater than 20 X 10(9)/L, the -CN method showed acceptable recovery of the mean but unacceptable imprecision. For WBC counts of 36-164 X 10(9)/L, the +CN method yielded acceptable Hb recovery with unacceptable imprecision. Hyperlipemia, resulting from addition of Intralipid directly to the blood samples, caused large errors in both H*1 methods.

It is necessary to develop methods for accurate monitoring of cell-free hemoglobin in circulation. Routine monitoring of circulating cell-free hemoglobin will be useful for evaluating the efficacy of blood substitute administration andfor determining the clearance rates of the blood substitute from circulation. In addition, discriminating between cell-free hemoglobin and cell-associated hemoglobin will enable accurate determination of RBC indices, mean cell hemoglobin and mean corpuscular hemoglobin concentration, in individuals receiving hemoglobin-based blood substitutes. As colorimetric methods used by hematology analyzers to quantitate the hemoglobin value of a blood sample cannot distinguish between cell-associated and cell-free hemoglobin, it is currently not feasible to quantitate the levels of hemoglobin substitutes in circulation. The advent of a technology that measures volume and hemoglobin concentration of individual RBCs provides an alternative strategy for quantitating the cell-associated hemoglobin in a blood sample. We document that the combined use of cell-based and colorimetric hemoglobin measurements provides accurate discrimination between cell-associated and cell-free hemoglobin over a wide range of hemoglobin levels. This strategy should enable rapid and accurate monitoring of the levels of cell-free hemoglobin substitutes in the circulation of recipients of these blood substitutes.

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