Abstract
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.
Highlights
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
We provide a review of the use of effective medium theory to describe the electrical conductivity of dilute particle suspensions in S2 Text
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
Summary
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. Polish physician Edmund Faustyn Biernacki invented a method of measuring the ESR in 1897 [1]. The Westergren ESR method is simple and inexpensive; it rapidly entered widespread use throughout the world. In the Westergren method [4], venous blood is mixed 4:1 with sodium citrate and collected in a glass or plastic tube with a minimum sedimentation scale of 200 mm and a minimum bore of 2.55 mm. At the end of 1 h, the distance from the lowest point of the surface meniscus to the top level of the red cell sediment is recorded as the ESR in mm/h
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