The determination of haemoglobin as cyanhaemiglobin or as alkaline haematin D-575. Comparison of method-related errors

In order to compare the accuracy of haemoglobin (Hb) determination methods, the commonly used cyanhaemiglobin (HiCN) method and the recently developed alkaline haematin D-575 (AHD) method (R. Zander, W. Lang & H. U. Wolf (1984) Clin. Chim. Acta 136, 83-93; H. U. Wolf, W. Lang & R. Zander (1984) Clin. Chim. Acta 136, 95-104) were tested with respect to method-related errors such as plasma, cell, and Hb errors. Both methods yield a series of more or less significant errors which generally lead to an overestimation of the Hb concentration in the order of 1%. However, in all three cases of plasma errors, i.e. normal plasma error, plasma error in lipaemic blood, and plasma error in bilirubinaemic blood, the AHD method shows significantly lower values of errors than the HiCN method. In the case of cell errors such as ghost and leukocyte errors, the overestimation of the Hb concentration by the HiCN method is 60% higher than that by the AHD method. In the case of Hb errors such as fetal Hb and carboxy Hb errors, there is a significant overestimation of the Hb concentration by the HiCN method, which amounts 3 min after mixing of blood and HiCN solution to 0.7% in the case of fetal Hb and to 13.2% in the case of carboxy Hb. The latter value yields an overestimation of 1.3%, when 10% carboxy Hb in a blood sample is present. In contrast, there is no detectable overestimation after 3 min in the case of the AHD method. Thus, the AHD method provides a higher accuracy in Hb determination than the commonly used HiCN method.