Abstract
Purpose :
Red blood cells (RBC) deformability was assessed at the single cell level to establish the deformability distributions in patients with diabetes (DM) with and without diabetic retinopathy (DR). By applying a uniaxial load at a moderate strain rate, we interrogated the extensional property of RBCs using a microfluidic cross-slot device to analyse the spectrum of the elongation index (EI) of the RBCs based on the assumption of normality across the different groups.
Methods :
Institutional ethics approval was obtained to analyse the rheological properties of the RBCs in patients with DM and different stages of DR. 20 subjects (5 age and sex matched healthy controls, 5 DM without DR, 5 with NPDR and 5 with PDR) were recruited from January 2016 through September 2016. Histograms of each patient group were plotted to visualize the RBC deformability distributions (n = 1400). The data was fitted with the automatic Gaussian peak analysis function in Origin (OriginLab, MA, USA), and column distribution statistics analyses were performed for each case.
Results :
The results demonstrated an apparent two-phase shift in the deformability of the RBCs. In the first phase, from the control to DM without DR, there was an emergence of a secondary peak with reduced deformability (EI = 1.46 ± 0.62). It is interesting to note that the primary peak (EI = 2.93 ± 1.35) coincides with the peak in the healthy control group (EI = 2.94 ± 1.29). From the DM without DR to the NPDR stage, the distribution re-assumes a unimodal profile, but with a leftward shift (EI = 2.62 ± 1.78). Interestingly, from the NPDR to PDR stage, there is another emergence of a very rigid subpopulation of RBCs (EI = 1.46 ± 0.65), corresponding to the same subpopulation in the DM cohort. The skewness and kurtosis values obtained from unimodal Gaussian curve fits revealed no apparent trend across the cases, and hence do not serve as good parameters to quantify the bimodality or severity of the disease progression. The resultant deformability distributions and fitted curves are shown in the Figure 1.
Conclusions :
In this pilot study, we discovered that RBCs from patients with DM and DR exhibited a bimodal distribution, possibly stemming from increased reticulocytosis. EI of RBCs from patients with DM and DR was significantly lower in comparison with normal healthy controls.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.