Correlations of Glycaemic Index and Estimated Whole Blood Viscosity with Blood Cell Indices in Diabetes Mellitus Management: A Clinical Laboratory Medicine Observational Cohort Study

<b>Background/Objective</b>: The risk of bleeding is part of blood flow pathophysiology in diabetes mellitus (DM), and there may be potential for the relationship between blood cell indices and estimated whole blood viscosity (eWBV) in DM. However, red blood cell (RBC) indices, platelet ratios, and lymphocyte ratios have been part of routine haematology tests in clinical medicine including diabetes management. This study investigated two research questions. Firstly, how does eWBV correlate with RBC indices, platelet ratios, and lymphocyte ratios? Secondly, which parameters of RBC in routine full blood count (FBC) correlate more with glycated haemoglobin (HbA1c) changes? <b>Methods</b>: This was a laboratory-based clinical observational cohort study using secondary data from ongoing research. Data collected included FBC and biochemistry (HbA1c and serum protein level). Dependent variables were platelet and lymphocyte ratios as well as eWBV. <b>Results</b>: Averages for all parameters in the cross-sectional data were within normal range, except high HbA1c (7.67%) and marginally high monocyte-to-lymphocyte ratio. In the periodic cohort analysis, only RBC distribution width showed a significant difference (<i>p</i> < 0.04) between cohort groups, but least correlated with HbA1c changes. Further analysis for correlations among change scores showed that RBC had the strongest positive linearity for HbA1c (r = 0.30) and among the top three for eWBV (r = 0.54), while mean cell volume (MCV) has the strongest inverse for HbA1c (r = -0.47). <b>Conclusions</b>: The ongoing clinical use of RBC variables is superior to profiles of platelet and/or lymphocyte ratios in assessing the potential risk of bleeding (i.e., hypo-viscosity) in diabetes.