The use of glycated haemoglobin (HbA1C) in determining glycemic control (and relevance of BMI) in diabetic patients in Ahmadu Bello University Teaching Hospital Zaria, Nigeria

Abstract

This study was carried out to specifically investigate the local HbA1_C level and determine extent of (if any) variation from the WHO (World Health Organization) recommended threshold for the diagnosis of diabetes and prediabetes using blood glucose as a benchmark. In addition, we also looked to see what role BMI (Body Mass Index) plays among subjects used for the study. 152 subjects were used for the study: 101 diabetic subjects and 51 non-diabetic control subjects. 5 mL of blood sample was collected from each of the subjects after about 8-10 h of overnight fasting. 3-4 mL of the sample was centrifuged and the serum analysed for glucose. The remaining 1-2 ml was transferred into EDTA bottles and analysed immediately for glycated haemoglobin (HbA1_C). The BMI (kg/m²) was calculated by dividing the weight in kilograms (kg) by the square of the height in metres (m²). For the BMI, no significant difference was observed between the diabetic subjects (mean = 25.75 kg/m²) and the non-diabetic control subjects (mean = 25.09 kg/m²). Thirty-seven (37) of the diabetic subjects and twenty-three (23) of the non-diabetic subjects had HbA1_C levels (mean = 6.96% and 6.29% respectively) that would imply either prediabetes or diabetes but were actually normal going by their fasting blood glucose (FBG) levels. A new chart for the interconversions between FBG and HbA1c and for predicting their expected values from each other was realized, drawn up and recommended for consideration in the management of diabetic patients along with the WHO recommended chart. There are a lot of normal individuals with HbA1c level that does not conform to (or that are simply higher than) what is regarded as the threshold for the onset of diabetes or prediabetes. Generally, the local (Nigerian) glycated haemoglobin (HbA1c) level can therefore be said to be distinctly higher for a given blood glucose range and should be taken as such in the management of diabetes in this environment. Being overweight or obese is not prerequisite to the development of diabetes or abnormal glycated haemoglobin level.

Keywords: BMI; Blood glucose; Diabetes; Glycaemic control; Glycated haemoglobin (HbA1c).