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. 2020 Apr 15;11:288. doi: 10.3389/fphys.2020.00288

TABLE 1.

Determination of the correlation between deformability and aggregation.

r R2 P (two-tailed) N
EImax vs. SS1/2 –0.7085 0.502 <0.0001 140
AI vs. t1/2 –0.8662 0.7504 <0.0001 121
EImax vs. AI 0.2126 0.0452 0.0192 121
EImax vs. AMP –0.119 0.01415 0.1937 121
EImax vs. t1/2 –0.1705 0.02906 0.0616 121
SS1/2 vs. AI –0.2607 0.06794 0.0039 121
SS1/2 vs. AMP 0.3482 0.1212 <0.0001 121
SS1/2 vs. t1/2 0.2511 0.06303 0.0055 121
Tr vs. EImax 0.5198 0.2702 <0.0001 121
Tr vs. AI 0.4282 0.1834 <0.0001 121
Tr vs. AMP –0.4547 0.2067 <0.0001 121
Tr vs. t1/2 –0.3129 0.09791 0.0005 121
Tr vs. SS1/2 –0.5874 0.3451 <0.0001 121
Ratio [SS1/2/EImax] vs. AI –0.2592 0.06716 0.0041 121
Ratio vs. AMP 0.2647 0.07006 0.0033 121
Ratio vs. t1/2 0.2392 0.05723 0.0082 121
Ratio vs. Tr –0.5918 0.3502 <0.0001 121
Ratio vs. EImax –0.8566 0.7338 <0.0001 140
Ratio vs. SS1/2 0.9658 0.9328 <0.0001 140

RBCs were isolated and their deformability and aggregation characteristics were determined by ektacytometry using a laser-assisted optical rotational cell analyzer (Lorrca Maxis, RR Mechatronics, Hoorn, Netherlands) as described previously (Cluitmans et al., 2012; Da Costa et al., 2016). Deformability was assessed using the elongation index (EI) at various shear stress (0.3 to 30 Pa), yielding the maximal elongation (EImax), i.e., the calculated EI at infinite shear stress, and SS1/2, i.e., the shear stress at which EI is half of the EImax. Aggregation characteristics are assessed using: (1) the shape recovery time Tr, i.e., the time needed by the RBCs to regain their normal shape (Dobbe et al., 2003) after undergoing a shear rate of 500 s–1 (shear stress of 1.5 Pa); (2) the aggregation index AI, defined as the decrease in intensity of scattered light during 10 s following disaggregation; (3) the t1/2, the rate at which aggregates are formed (Da Costa et al., 2016). Blood was obtained with informed consent and the studies were carried out as described before (De Franceschi et al., 2011; Dinkla et al., 2012; Cluitmans et al., 2015, 2016), in accordance with the CCMO guidelines of the Medical Ethical Committee of the Radboud University Medical Center (file numbers 2007-148, 2013-381, 2018-4421).