Correlation of estimated average glucose with single point glucose values in patients attending a clinical laboratory facility in South-Western Nigeria: a retrospective study

Abstract

Regular monitoring of glycaemic levels in patients with diabetes mellitus forms a major fulcrum for ensuring a desirable treatment outcome and a good quality of life in affected individuals. Glycated haemoglobin (HbA1c) measurement is a common and dependableoption for determining long-term glycaemic control. Unfortunately, it is relatively expensive and not readily available in most low- ncome settings. Measuring fasting plasma glucose (FPG) is the cheaper alternative if it correlates with HbA1c. A retrospective study into clinical records to identify all patients who had HbA1c and FPG was conducted on the same day between January 2021 and July 2022. Estimated average glucose was calculated from the HbA1c and the values were correlated with the FPG. Factors predicting values for HbA1c were also determined. The results obtained showed that a total of 315 patients had clinical records required for the study, 147(46.7%) males and 168 (53.3%) females. They were grouped into diabetic (n=111, with median FPG of 155 mg/dL), impaired fasting glucose (n=67, with median FPG of 108 mg/dL) and non-diabetic (n=137, with median FPG of 92 mg/dL) participants. The estimated average glucose for the three groups was 160 mg/dL, 117 mg/dL and 112 mg/dL, respectively. The FPG of the diabetic group showed a moderate correlation with the estimated average glucose (0.630 and a p-value < 0.001), and factors which predicted a high HbA1c were increasing age, FPG and the presence of diabetes mellitus. This data further encourages the continued use of FPG in monitoring glycaemic control in diabetic patients, especially in resource-poor locations where HbA1c is either too expensive or unavailable.