Diagnostic tool for red blood cell membrane disorders: Assessment of a new generation ektacytometer

Abstract

Inherited red blood cell (RBC) membrane disorders, such as hereditary spherocytosis, elliptocytosis and hereditary ovalocytosis, result from mutations in genes encoding various RBC membrane and skeletal proteins. The RBC membrane, a composite structure composed of a lipid bilayer linked to a spectrin/actin-based membrane skeleton, confers upon the RBC unique features of deformability and mechanical stability. The disease severity is primarily dependent on the extent of membrane surface area loss. RBC membrane disorders can be readily diagnosed by various laboratory approaches that include RBC cytology, flow cytometry, ektacytometry, electrophoresis of RBC membrane proteins and genetics. The reference technique for diagnosis of RBC membrane disorders is the osmotic gradient ektacytometry. However, in spite of its recognition as the reference technique, this technique is rarely used as a routine diagnosis tool for RBC membrane disorders due to its limited availability. This may soon change as a new generation of ektacytometer has been recently engineered. In this review, we describe the workflow of the samples shipped to our Hematology laboratory for RBC membrane disorder analysis and the data obtained for a large cohort of French patients presenting with RBC membrane disorders using a newly available version of the ektacytomer.

Osmotic gradient ektacytometry: A valuable screening test for hereditary spherocytosis and other red blood cell membrane disorders

“…Osmotic gradient ektacytometry, originally designed in the seventies, has been for many years the reference method for RBC deformability measurement but, due to its technical complexity and lack of implementation, was not used for clinical purposes. However, the new generation ektacytometer LoRRca MaxSis (Mechatronics Instruments BV ® , Zwaag, The Netherlands) has become a more robust and user friendly equipment allowing the transference from research to clinical laboratory requiring harmonization for its inclusion in the diagnostic algorithm for HS and other RBC membrane disorders …”

Genotype-phenotype correlations in hereditary elliptocytosis and hereditary pyropoikilocytosis

“…Ektacytometry is an objective reference technique that can aid in the diagnosis of RBC membrane disorders [6]. In ektacytometry, the deformability of the patient's RBCs is assessed based on their laser diffraction pattern while they are subjected to a defined value of shear stress and an increasing osmotic gradient [7, 8]. The resulting ektacytometry curve reflects biomechanical properties of the RBCs including osmotic fragility, surface-to-volume ratio, cytoskeleton flexibility, and cytoplasmic viscosity.…”

“…The resulting ektacytometry curve reflects biomechanical properties of the RBCs including osmotic fragility, surface-to-volume ratio, cytoskeleton flexibility, and cytoplasmic viscosity. The typical HE ektacytometry curve is trapezoidal with decreased RBC deformability, while a larger decrease in deformability is noted in HPP (Figures 2 and 3) [4, 8]. …”

Hemoglobin C trait accentuates erythrocyte dehydration in hereditary xerocytosis

“…Osmotic gradient ektacytometry (LoRRca MaxSis) revealed a pattern consistent with erythrocyte dehydration in the proband and both parents, with the proband's erythrocytes more severely affected than either parent (Fig. ) …”

“…Several unexpected observations were made when performing diagnostic studies: (i) Erythrocytes from the proband and his mother had evidence of dehydration, with the dehydration of the proband's erythrocytes much more severe than his mother's, even though both have the same PIEZO1 mutation. (ii) Erythrocytes from the proband's father also exhibited dehydration (elevated MCHC, leftward shifted ektacytometry), and while he does not have a PIEZO1 mutation, he has hemoglobin AC . The proband has both HX and hemoglobin AC contributing to the marked erythrocyte dehydration phenotype.…”