Sensitivity of the cell transit analyzer (CTA) to alterations of red blood cell deformability: Role of cell size-pore size ratio and sample preparation

The sensitivity of the Cell Transit Analyzer (CTA) to the alterations of red blood cell (RBC) deformability and related factors was investigated. Using 5 μm pore size filters the CTA was found to be more sensitive to slight glutaraldehyde-induced decreases of deformability for rat RBC in comparison with larger human RBC. However, using 3 μm pore size filters decreased the sensitivity of measurements to mechanical changes of rat RBC, implying that a lower cel/pore size ratio might provide better sensitivity. Exclusion of a subpopulation of the most rigid cells, which are not able to pass through the pores might be involved. Measurements using RBC suspensions with various cell counts revealed that RBC concentration in the suspension being filtered was an important determinant of CTA sensitivity, especially for measurements on human RBC using 5 μm pore size filters. The insensitivity of CTA to slight changes in deformability might, in part, be related to the higher probability of longer pulses being rejected as a result of coincidence. Either decreasing the cel/pore size ratio or limiting the cell count in the suspensions being filtered might optimize the sensitivity of the CTA to slight degrees of mechanical alterations in human RBC.