Detection of haemoglobin variants and inference of their functional properties using complete oxygen dissociation curve measurements

Complete oxygen dissociation curves for red cell suspensions of three haemo globinopathies, namely haemoglobin (Hb) H, Hb Koln and Hb Tak/beta thalassa emia diseases, were measured using automatic recording methods. These curve s were left-shifted compared with the normal red cell curve and showed a bi phasic shape as a result of co-existence of the high and normal affinity ha emoglobin components. Computer-assisted simulation of these biphasic curves enabled us to infer the curves for the pure abnormal haemoglobins and thei r fraction in the total haemoglobin of the red cell. The inferred values of fraction agreed with those determined by haemoglobin type analysis or the literature values. The curve for Hb Koln red cells deviated from the normal red cell curve in the whole range of oxygen saturation, whereas the curve for Hb H was close to the normal curve at the middle and upper portions. Th is difference in deviation was ascribed to a possible interaction between H b Koln and Hb A through subunit exchange, and its absence between Hb H and Hb A. The present results indicate that measurement of the complete oxygen dissociation curve is important for the detection of non-interacting varian ts such as Hb H and is useful for inferring the functional properties of ha emoglobin components that are not easily isolated.