Evaluation of Plasma Glucose Estimations as Reliable Economical Surrogate for HbA1c in Monitoring Glycaemic Status of T2DM Patients: A Retrospective Study

Introduction: In Low and Middle Income Countries (LMIC) like India, either Fasting Plasma Glucose or Postprandial Plasma Glucose (FPG/PPG) estimations were adopted as surrogate alternative to Glycated Haemoglobin (HbA1c) in Type 2 Diabetes Mellitus (T2DM). However, the reliability of this correlation remains ambiguous due to lack of consensus among the previous studies. Aim: To determine the correlation of FPG and PPG as well as their calculated mean with HbA1c in T2DM subjects for monitoring glycaemic status. Materials and Methods: A single centre, retrospective, cross- sectional data survey was carried out for a sampling frame of 13 months (August 2017 to August 2018) encompassing 1268 T2DM subjects. The data was collected during September 2018 to March 2019 and subsequently analysed during April 2019 to August 2019. The analysis was carried out in two approaches. In the first approach: the data was segregated into two major groups and six subgroups to understand relative concordance and discordance percentage; sensitivity, specificity and accuracy; and absolute and percentage difference recruiting relevant statistical tools. In the second approach, Area Under Curve (AUC) of Receiver Operating Characteristic (ROC) curves were employed to understand changes in FPG/PPG/calculated mean with increasing severity of T2DM. Results: With increasing severity of T2DM (HbA1c), not only gradual exacerbation of underestimation in FPG and overestimation in PPG but also declination of sensitivity in either of them was apparent. Though calculated mean of FPG and PPG measurements appended with intermittent features yet mimics PPG. AUC of ROC analysis revealed relatively high PPG levels at lower HbA1c levels and its replacement with FPG with increasing HbA1c levels. Conclusion: An integrated utility of both FPG and PPG as tuning tools of treatment modalities to achieve desired HbA1c levels in T2DM could be a promising approach.