BackgroundCompare glycated hemoglobin (HbA(1c)) diagnostic tests for prediabetes and diabetes with plasma glucose criteria and compare the metabolic profiles of people classified by HbA(1c) versus by glucose levels. MethodsParticipants were recruited for the San Juan Overweight Adults Longitudinal Study. The participants were primarily Hispanic (98%), without previously diagnosed diabetes, and aged 40 to 65years. Participants classified as normal glycemic, prediabetes, or diabetes on the basis of baseline HbA(1c) and plasma glucose criteria were compared with respect to baseline cardiometabolic factors. ResultsThe 1342 participants had a mean age of 50.56.8years and 28% were men. Thirty-one percent were diagnosed with prediabetes by plasma glucose criteria and 53.4% by HbA(1c), and 8.1% were diagnosed with diabetes by plasma glucose criteria and 6.3% by HbA(1c); overall concordance rate was 55.1%. The area under the receiver operating characteristic curve of HbA(1c) compared to plasma glucose criteria was 0.62 for impaired glucose and 0.76 for diabetes. A worse cardiometabolic profile was seen within subgroups that met HbA(1c) and plasma glucose criteria for diabetes or prediabetes. Those diagnosed with prediabetes by plasma glucose criteria had significantly higher systolic blood pressure and higher homeostatic model assessment than those diagnosed using HbA(1c). Participants diagnosed with diabetes by plasma glucose criteria had lower body mass index, smaller waist circumference, and lower insulinogenic and disposition indices, but higher homeostatic model assessment of insulin resistance, than those diagnosed by HbA(1c). ConclusionsLow concordance was seen between HbA(1c) and glucose measurements. The HbA(1c) is not a good test for prediabetes but shows reasonable validity for diabetes in this high-risk predominantly female Hispanic population. People classified by HbA(1c), plasma glucose criteria, or both show different metabolic profiles; a combined test may be ideal.