Date Published: June 5, 2015
Publisher: Public Library of Science
Author(s): Alexander Zhbanov, Sung Yang, Gordon Langsley.
The erythrocyte sedimentation rate (ESR) test has been used for over a century. The Westergren method is routinely used in a variety of clinics. However, the mechanism of erythrocyte sedimentation remains unclear, and the 60 min required for the test seems excessive. We investigated the effects of cell aggregation during blood sedimentation and electrical conductivity at different hematocrits. A sample of blood was drop cast into a small chamber with two planar electrodes placed on the bottom. The measured blood conductivity increased slightly during the first minute and decreased thereafter. We explored various methods of enhancing or retarding the erythrocyte aggregation. Using experimental measurements and theoretical calculations, we show that the initial increase in blood conductivity was indeed caused by aggregation, while the subsequent decrease in conductivity resulted from the deposition of erythrocytes. We present a method for calculating blood conductivity based on effective medium theory. Erythrocytes are modeled as conducting spheroids surrounded by a thin insulating membrane. A digital camera was used to investigate the erythrocyte sedimentation behavior and the distribution of the cell volume fraction in a capillary tube. Experimental observations and theoretical estimations of the settling velocity are provided. We experimentally demonstrate that the disaggregated cells settle much slower than the aggregated cells. We show that our method of measuring the electrical conductivity credibly reflected the ESR. The method was very sensitive to the initial stage of aggregation and sedimentation, while the sedimentation curve for the Westergren ESR test has a very mild slope in the initial time. We tested our method for rapid estimation of the Westergren ESR. We show a correlation between our method of measuring changes in blood conductivity and standard Westergren ESR method. In the future, our method could be examined as a potential means of accelerating ESR tests in clinical practice.
The determination of the erythrocyte sedimentation rate (ESR) is a useful hematological test because it provides a measure of the patient’s inflammatory or acute-phase response. The Polish physician Edmund Faustyn Biernacki invented a method of measuring the ESR in 1897 . Later, similar methods were also reported by Robert Sanno Fåhræus in 1918  and Alf Vilhelm Albertsson Westergren in 1921 . The Westergren ESR method is simple and inexpensive; it rapidly entered widespread use throughout the world.
In this study, we investigated changes in blood conductivity during aggregation and sedimentation, using a system consisting of a small chamber with two planar electrodes on the bottom. As measured experimentally, the conductivity of blood in the chamber increased slightly during the first minute of observation and decreased thereafter for more than 1.5 h. We hypothesized that the slight increase in the blood conductivity within the first minute is due to erythrocyte aggregation.