P1550: NEW GENERATION EKTACYTOMETRY STUDY OF RED BLOOD CELLS RHEOLOGICAL PARAMETERS IN HEMOGLOBINOPATHIES

Background: Next Generation Ektacytometry is up to now one of the best complementary diagnostic tool for hereditary rare anemias due to red cell defects. Impairment of red cell deformability leading to the decrease of red cell survival rate, is the common trait of hereditary haemolytic anemias and some hemoglobinopathies In general this is the consequence of the abnormal cell shape, increased rigidity or dehydration. Classical examples of this situation are HS, unstable hemoglobinopathies, sickle cell disease and homozygous b-thalassemia (BT) but up to now, the OGE experience with structural hemoglobinopathies and thalassemia is scarce Aims: We have evaluated the OGE profiles in 70 patients with different hemoglobinopathies, both structural and thalassemia, with the aim to analyse their usefulness for the early diagnosis of these disorders either individual or in coinheritance with other hereditary RBC defects. In addition this study aims to improve our knowledge of the contribution of red cell deformability, osmotic fragility and intracellular viscosity to the pathophysiology of hemolysis especially when these disorders are a cause of rare anemia Methods: The patients included in this study have been studied via a stepwise process including RBC morphology, high performance liquid chromatography (HPLC) complemented by Hb electrophoresis, and the measurement of common RBC enzyme activities.When necessary, the genetic diagnosis of hemoglobinopathies was performed by t-NGS. OGE provided by the osmoscan module of the Laser Optical Rotational Red Cell Analyser (LoRRca) MaxSis provides four main parameters1. The elongation index (EImax), that depends mostly of the cytoskeleton mechanics 2. The osmotic fragility (Omin) that depends on the surface-to-volume ratio (S/V), 3. The RBC hydration status (Ohyper) that depends of the intracellular viscosity or hemoglobin concentration (MCHC) and 4. The area under the curve (AUC) or the distance between the starting point in the hypo-osmolar region (Omin) and an ending point in the hyper-osmolar region (Ohyper) that partially depends of red cell deformability Results: Exception made of HbE, in all the structural hemoglobinopathies and thalassemia the tail of the osmoscan curve shifts to the left suggesting the existence of a decreased osmotic fragility and dehydration. Significantly decreased (p<0.01) parameters have been found for EImax in HbC, HbSS and BT, Omin in HbC, HbS, HbSS, HbSC and BT, Ohyper in all hemoglobinopathies and AUC in HbC, HbSS and BT. The OGE curves of all the hemoglobinopathies are shown in the FIGURE Image:Summary/Conclusion: The RBC shape and, hemoglobin concentration are important factors that contribute to maintaining the hydration/dehydration equilibrium, the osmotic fragility and cell rigidity. A characteristic of all structural hemoglobinopathies, exception made of HbE, and of BT is the decreased red cells osmotic fragility (Omin) and dehydration (Ohyper) that is specially marked for HbC, HbSS and BT. In HbC and HbSS this effect is probably due to the ion transport dysfunction created by the Hb polymerization and Hb crystallization respectively,whereas in BT it may be the consequence of an excess of alpha chains due to the imbalance of beta and alpha chains synthesis. We can conclude that, in contrast with RBC membrane defects, the Osmoscan profile do not allow a clear differentiation between hemoglobinopathies including BT. However, it provides a complementary information on red cells rheological behavior characterized by a decreased deformability and dehydration