6 Lorrca deformability clean-up
Channel: Jan de Zoeten RRM
Date: 10/05/2015

The capacity of RBC’s to deform is a powerful indicator of their viability as it is essential for the optimal circulation of these cells both in micro- and macrocirculation. This deformability depends on three important cell properties.
• Surface area to volume ratio
• Viscoelastic properties of the membrane
• The viscosity of the intracellular fluid

Measurement
Red blood cell deformability is expressed as the Elongation Index (El) measured in polyvinylpyrrolidone (PVP) medium of known viscosity and presented in a EI versus shear stress deformability curve. A thin layer of RBC’s is sheared between two concentric cylinders and a certain, but exactly known, shear stress is applied to the cells (by rotation of the outer cylinder; the cup).
The RBC’s will change, in an iso-osmotic environment, from oval biconcave disks to its elongated shape. Because of the osmotic variety of the medium (50-500 mOsm/kg) during the measurement, continuous deformation occurs which is measured by a laser beam diffraction pattern; captured with a video camera and analyzed by a computer. For this test only 25 μl of blood is needed.

Lorrca Maxsis osmoscan is a unique instrument which combines Red Blood Cell (RBC) deformability by ektacytometry, osmoscan and aggregometry; all temperature controlled. It is capable of fully automated measurement and calculation of various phenomena of RBC’s by analysis of their rheological behavior. The technique accurately detects deformability as a function of shear stress, pre-hemolytic stability and aggregation of the RBC’s and is of added value for hematology analysis.