Comparing glucose and hemoglobin A_1c diagnostic tests among a high metabolic risk Hispanic population

Abstract

AIMS Compare HbA1c diagnostic tests for pre-diabetes and diabetes with plasma glucose criteria (PGC), and compare the metabolic profiles of people classified by HbA1c versus by glucose levels. METHODS Participants were recruited for the San Juan Overweight Adults Longitudinal Study (SOALS). Were primarily Hispanic (98%), without previously diagnosed diabetes, and aged 40–65 years. Participants classified as normal glycemic, pre-diabetes or diabetes based on baseline HbA1c and PGC, were compared with respect to baseline cardiometabolic factors. RESULTS The 1,342 participants had a mean age of 50.5±6.8 and 28% were men. Thirty-one percent were diagnosed with pre-diabetes by PGC and 53.4% by HbA1c, 8.1% were diagnosed with diabetes by PGC and 6.3% by HbA1c; overall concordance rate was 55.1%. The area under the ROC curve (AUC) of HbA1c compared to PGC was 0.62 for impaired glucose and 0.76 for diabetes. A worse cardiometabolic profile was seen within subgroups that met HbA1c and PGC criteria for diabetes or pre-diabetes. Those diagnosed with pre-diabetes by PGC had significantly higher systolic blood pressure and higher HOMA than those diagnosed using HbA1c. Participants diagnosed with diabetes by PGC had lower BMI, smaller waist circumference, lower insulinogenic and disposition indices, but higher HOMA-IR, than those diagnosed by HbA1c. CONCLUSIONS Low concordance was seen between HbA1c and glucose tests. The HbA1c is not a good test for pre-diabetes, but shows reasonable validity for diabetes in this high-risk predominantly female Hispanic population. People classified by HbA1c, PGC, or both show different metabolic profiles; a combined test may be ideal.

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