Simultaneous measurement method of erythrocyte sedimentation rate and erythrocyte deformability in resource-limited settings

Objective: The individual effects of plasma and red blood cells (RBCs) on the biophysical properties of blood can be monitored by measuring the erythrocyte sedimentation rate (ESR) and RBC deformability simultaneously. However, the previous methods require bulky and expensive facilities (i.e. microscope, high-speed camera, and syringe pump) to deliver blood or capture blood flows. Approach: To resolve these issues, a simple method for sequential measurement of the ESR and RBC deformability is demonstrated by quantifying the cell-free volume (VCF), cell-rich volume (VCR), and blood volume (VB) inside an air-compressed syringe (ACS). A microfluidic device consists of multiple micropillar channels, an inlet, and outlet. After the ACS is filled with air (Vair = 0.4 ml) and a blood sample (VB = 0.6 ml, hematocrit = 30%) sequentially, the ACS is fitted into the inlet. The cavity inside the ACS is compressed to Vcomp = 0.4 ml after closing the outlet with a stopper. A smartphone camera is employed to capture variations in the VCF, VCR, and VB inside the ACS. The ESR index suggested in this study (ESRPM) is obtained by dividing the VCF (t = t1) with an elapse of t1. By removing the stopper, ΔVB (ΔVB = VB [t = t1] − VB) is obtained and fitted as a two-term exponential model (. As a performance demonstration, the proposed method is employed to detect an ESR-enhanced blood sample, homogeneous hardened blood sample, and heterogeneous blood sample. Main results: From the experimental results, it is found that the proposed method has the ability to detect various bloods by quantifying the ESRPM and two coefficients (a, b) simultaneously. Significance: In conclusion, the present method can be effectively used to measure the ESR and RBC deformability in resource-limited settings.