Haemoglobinometry on automated haematology analysers.

It is generally recognized that the standardized cyanmethaemoglobin (HiCN) method is the preferred method for the determination of haemoglobin in blood. In automated analysers, however, the reaction time available before the photometric measurement is too short. With the Ortho ELT800 we found that the conversion into HiCN took longer than 25 s. More important was the variation of results with the haemoglobin derivatives present in the blood sample. Our experiments suggest that Coulter counters and other automated analysers as well use denaturated globin haemichrome as the end product in their haemoglobin procedure although they profess to use HiCN by the addition of cyanide to the reagents. However, haemichrome is a suitable alternative for automated analysers as the conversion time is very short for all haemoglobin derivatives including HbCO. In the Coulter S Plus III where white cell size distribution analysis and haemoglobin determination are performed in the same solution, the haemoglobin derivative formed shortly after mixing is not a stable one. White cell size analysis and haemoglobin determination should preferably be performed in separate channels with different lysing reagents giving optimal conditions for each determination. Evaluation of the analysers would be easier if the manufacturers would give correct information on the chemistry of the haemoglobin method and state the composition of the reagents used.