A standardized parameter for the distribution of individual Red Blood Cell deformability with the Cell Transit Analyzer

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The purpose of this study was to identify a parameter allowing the standardization of the Cell Transit Analyzer (CTA) in order to study the individual deformability of each explored Red Blood Cell (RBC). Using theoretical arguments based on the principle of the CTA, we calculated the thickness "x" of the crown of fluid surrounding each RBC during its entry phase into the micropore. A mathematical equation (x = 62.5/magnitude of dU) was established between the difference of potential (dU, mV) that occurs during this phase and the corresponding thickness ("x", micron) of the crown. By exploring fresh control RBCs of healthy subjects and assuming that the rigid RBCs proportion in a fresh blood sample of healthy subject is less than 3.5%, we performed a thresholding of "x" to distinguish rigid RBC from deformable ones. That thresholding was necessary to stamp the variability of counts linked to polycarbonate filters (PF) used to carry out measures. According to the PF, the value of the threshold "Tx" provided by the thresholding ranged between 0.222 and 0.246 micron. Using the values of "Tx", we counted approximately 10-25% rigid RBCs in the pathological samples of four patients with sickle cells SS disease and of one diabetic patient with splenomegaly. We observed in addition that the percentages of rigid RBCs counted after thresholding are identical from a filter to another one with an absolute error less than 2% in fresh RBCs (normal or pathological) samples. We concluded that the method of standardization by thresholding presented here could be used in clinic routine to count the rigid RBCs percentage contained in a given sample.