Discrepancies between Glycated Hemoglobin and Fasting Plasma Glucose in New-onset Diabetes Mellitus

Background Fasting plasma glucose (FPG) and glycated hemoglobin (HbA1c) are commonly used for diagnosing diabetes mellitus in Nepal. Though HbA1c criteria are convenient for diagnosis there is a discrepancy between the fasting plasma glucose and HbA1c for diagnosis. Objective To assess the comparability between fasting plasma glucose and glycated hemoglobin levels in the new-onset diabetes mellitus. Method This is a hospital-based descriptive cross-sectional study including 128 newly diagnosed diabetes mellitus conducted at Dhulikhel Hospital, Kathmandu University Hospital. New onset diabetes patients above 18 years of age who met inclusion criteria were included. The clinical characteristics and biochemical parameters were analyzed. Statistical analysis was done using student's t-test and correlation coefficient. Result There were 128 newly diagnosed diabetes mellitus patients included in the study among which 57.0% were males with a mean age of 49.48±11.40 years. The mean fasting plasma glucose, postprandial sugar (PPBS), and glycated hemoglobin were 205.54±88.93 mg/dL, 331.08±146.61 mg/dL, and 9.59±2.70% respectively. Diabetes was diagnosed using fasting plasma glucose, and glycated hemoglobin criteria in 84.4% and 90.6% of patients. In new-onset diabetic patients, 76.56% of patients had both elevated levels of fasting plasma glucose and glycated hemoglobin. Of the diabetic patients who had fasting plasma glucose ≥126 mg/dL, 90.7% of patients had HbA1c ≥ 6.5% whereas 1.6% of new-onset diabetes had < 126 mg/dL and glycated hemoglobin < 6.5%. There was a strong correlation between fasting plasma glucose and glycated hemoglobin (r=0.723; p<0.01). Conclusion Both fasting plasma glucose and glycated hemoglobin tests have to be used together for diagnosing diabetes mellitus.