Assessment of Glycated Haemoglobin and Fasting Blood Glucose in the Diagnosis of Type 2 Diabetes Among Adults in Osun State, South West Nigeria

The diagnosis of type 2 diabetes relies on accurate and reproducible laboratory tests, with glycated haemoglobin and fasting blood glucose both widely used, though their comparative utility in Nigerian clinical settings remains understudied. This study compared HbA1c and fasting blood glucose in diagnosing type 2 diabetes among adults attending a general hospital in Oshogbo, Osun State, South West Nigeria. A cross-sectional study was conducted among 300 adults aged 30 years and above without prior diabetes diagnosis. Fasting venous blood was collected for estimation of fasting blood glucose by glucose oxidase method and HbA1c by ion-exchange high-performance liquid chromatography. World Health Organisation diagnostic criteria were applied. Using fasting blood glucose as the reference, HbA1c demonstrated sensitivity of 85.7%, specificity of 93.2%, and a kappa agreement coefficient of 0.78. New diabetes diagnoses were made in 11.0% and impaired fasting glucose in 17.3% of participants. HbA1c identified additional cases missed by fasting blood glucose alone, particularly in individuals with haemoglobinopathies warranting cautious interpretation. Age above 50 years and obesity were strongly associated with abnormal results. The study supports the combined use of HbA1c and fasting blood glucose for diabetes screening in community settings and recommends establishment of diabetes screening clinics at primary health facilities across South West Nigeria. Keywords: HbA1c, fasting blood glucose, type 2 diabetes, diagnosis, Osun State