Osmotic Gradient Deformability by Ektacytometry
The deformability of erythrocytes (RBC) is measured in an ektacytometer, a laser-diffraction viscometer, as a continuous function of suspending medium osmolality. The ability of the RBC (diameter 6-8 µm) to pass through the microvasculature (openings of 2-3 µm) and splenic sinuses (openings of 0.5-1.0 µm) is referred to as deformability.
The resultant osmotic deformability profiles provide information on the viability of RBC, cellular water content, surface area, deformability of the cell, heterogeneity within these cellular properties, and several pathological conditions, which are characterized by typical shifts in this curve.
The osmotic deformability curve can be described by three parameters:
1) Omin is the osmolality at which the minimum deformability index (DI) is reached. This value is related to the surface area to volume ratio of the cell and has been found to equal the 50% hemolysis point in the classical osmotic deformability test.
2) Dimax is the maximum value of the deformability index, normally reached around 290 mosmol (the physiologic osmolality value). This indicates the maximum deformability of the cell under shear stress and is related to a number of factors, such as surface area, volume, internal viscosity, and mechanical properties of the cell membrane.
3) Ohyp is the osmolality at which the DI reaches half of its maximum value. This gives an indication of the position of the hypertonic part of the curve, which is related to the internal viscosity of the cell as well as mechanical properties of the membrane, such as how it will bend under force (stiffness)
Figure 1: This ektacytometric curve shows a population of red blood cells with a deformability that does not indicate a red blood cell membrane disorder.
Figure 2: This ektacytometric curve shows a population of red blood cells with abnormal membrane characteristics indicative of spherocytosis.
Figure 3: This ektacytometric curve shows a population of red blood cells with an abnormal deformability that is consistent with eliptocytosis.
To send samples, see Ektacytometry Request Form for the requsition.
See Osmotic Deformability Profile by Ektacytometry for the licencing, pricing, and shipping information specific to this test. Price includes all materials labor, reporting and institutional overhead.
See Sample Collection Requirements – ACD for general sample collection and shipment requirements.