Impact of Erythrocyte Indices on Glycated Haemoglobin and Plasma Glucose Discordance in Non-diabetics: A Retrospective Study

Introduction: Glycated Haemoglobin (HbA1c) has evolved into one of the most essential tools for the diagnosis and followup of Diabetes Mellitus (DM). Discordance between plasma glucose and HbA1c is being observed, especially in individuals diagnosed with prediabetes. Different types of anaemia, such as iron deficiency, haemolytic, and megaloblastic anaemia, can affect HbA1c results. Aim: To study the effect of erythrocyte indices on the levels of HbA1c, particularly in situations where HbA1c levels are discordant with plasma glucose. Also, to derive the cut-off value of Red Blood Cells (RBC) indices below or above which the HbA1c results will be affected. Materials and Methods: The present retrospective analytical study was conducted at Sri Ramachandra Institute of Higher Education and Research, Chennai, Tamil Nadu, India. from March to August 2023. Out of 495 non-diabetic individuals recruited, those whose HbA1c value matched their plasma glucose value were categorised under the concordant group (n=285), and the rest under the discordant group (n=210). Retrospective data, including Fasting Plasma Glucose (FPG), HbA1c, Haemoglobin (Hb), Packed Cell Volume (PCV), Erythrocyte Sedimentation Rate (ESR), Mean Corpuscular Volume (MCV), Mean Corpuscular Haemoglobin (MCH), Mean Corpuscular Haemoglobin Concentration (MCHC) were collected and compared between the groups. Statistical analysis was performed using the MannWhitney U test and Spearman’s rho correlation via Statistical Package for Social Sciences (SPSS) Version 20. Results: The study population had a mean age of 43.2±11.3 years, comprising 319 males (64.4%) and 176 females (35.5%). For identical FPG ranges in both groups, the discordant group had higher median HbA1c values compared to the concordant group (p