Comparing glucose and hemoglobin A1c diagnostic tests among a high metabolic risk Hispanic population

Abstract

Background: Compare 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.

Methods: Participants were recruited for the San Juan Overweight Adults Longitudinal Study. The participants were primarily Hispanic (98%), without previously diagnosed diabetes, and aged 40 to 65 years. 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.

Results: The 1342 participants had a mean age of 50.5 ± 6.8 years 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 .

Conclusions: Low 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.

Keywords: HbA1c; IGT; diabetes; diagnosis; ethnicity.

Figure 1. Pre-diabetes and Diabetes Prediction of HbA1c compared to OGTT

(a) ROC curve for pre-diabetes prediction of HbA1c compared to OGTT (b) ROC curve for pre-diabetes prediction of HbA1c compared to OGTT adjusted for age, gender and smoking, (c) ROC curve for diabetes prediction of HbA1c compared to OGTT (d) ROC curve for pre-diabetes prediction of HbA1c compared to OGTT adjusted for age, gender and smoking.