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.
Ektacytometry Links
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.
EXAMPLE OF CLINICAL/RESEARCH REPORT
Children's Hospital Oakland Research Institute
Red Cell Membrane Laboratory Report
Patient:
Date of Study:
From:
Physician:
Age:
MR #:
Osmotic Gradient Ektacytometry:
Test result:
See Profile and table Attached :The table indicates the osmolality at
which 50% of the cells hemolyze (Omin), the maximal deformability of the cells
(DImax) and the osmolality at which the deformability equals half the maximum
value (Ohyp) in comparison to normal values.
Interpretation and recommendations:
The Omin is normal, DImax is normal and the Ohyp is normal.
The pattern of the ektacytometric deformability curve is consistent with a
normal red cell membrane.
----------------------------Carolyn Hoppe, M.D.
Hematologist
(510) 428-3193
Lab Director: Bertram Lubin, M.D. (510) 428-3502; FAX (510) 601-3928