Comparison of Devices That Measure Sickle Red Cell Deformability

• Published in: Blood 2023-11, Vol.142 (Supplement 1), p.3669-3669
• Main Authors: Patwardhan, Akshay A, Oshabaheebwa, Solomon, Delianides, Christopher A., Sekyonda, Zoe, Patel, Ashwin P, Evans, Erica N, Yoo, Justin J, Abel, Lindsey, Suster, Michael A., Mohseni, Pedram, Gurkan, Umut A., Sheehan, Vivien A
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2023-187557

Background With the emergence of novel pharmacologic and gene-based therapies, identifying the rheological and biophysical RBC abnormalities of sickle cell disease (SCD) not captured by clinical laboratory techniques is crucial. Ektacytometry (LORRCA), the current standard to assess RBC function, does not reflect mechanical stress that RBCs experience in capillary microvasculature in the body. The device is costly, requires a nitrogen gas tank, and its use is difficult to translate outside of large-scale laboratory settings. In comparison, the Microfluidic Impedance Red Cell Assay (MIRCA) is a low-cost, portable device that mimics capillary microvasculature with micropillar arrays spaced 3-12 µm apart. Thus, MIRCA measures mechanical deformability, which is more physiologic, mimicking RBCs squeezing through microvasculature. An impedance analyzer calculates the MIRCA Occlusion Index (OI), representing the % occlusion of the chip. Here we compare the MIRCA to the LORRCA, assessing the correlations of OI and Elongation Index maximum (EI) to conventional laboratory tests and SCD related complications. Methods Peripheral blood from 53 adult (n = 28) and pediatric (n = 25) individuals (HbSS = 35, HbSB0 = 6, HbSC = 5, HbSB0 = 1, and HbAA controls = 6) were obtained under an Emory University IRB approved protocol. Patients transfused < 90 days prior were excluded. Hospitalizations / emergency department (ED) visits for pain within 12 months of sample collection were determined by chart review. Samples were collected in EDTA, stored at 4°C up to 48 hours, centrifuged at 500g, washed, and resuspended to a 20% hematocrit to run on MIRCA, an oxygen gradient ektacytometer (LORRCA), and an ADVIA hematology analyzer. Polydimethylsiloxane (PDMS) fabricated MIRCA chips were bonded to a standard glass slide with pairs of gold-sputtered electrodes adjacent to each array. Chips were prepared by perfusing ethanol, 1X phosphate-buffered saline (PBS), and 3% bovine-serum albumin (BSA) in 1X PBS via syringe pump and were incubated overnight at 4°C prior to use. Baseline impedance was taken for a 2-minute perfusion of 1X PBS, then OIs were calculated from impedance values 10 minutes after sample introduction normalized to baseline. The data was analyzed using the Mann-Whitney U test, Spearman correlation, and linear regression. OriginPro (Northampton, MA, USA) and Stata 18 (College Station, TX, USA) were used for the analyses and a p < 0.05 was considered significant. Results The