Hemoglobin A1c as a Screen for Previously Undiagnosed Prediabetes and Diabetes in an Acute-Care Setting

OBJECTIVE: Hemoglobin A(1c) (HbA(1c)) is recommended for identifying diabetes and prediabetes. Because HbA(1c) does not fluctuate with recent eating or acute illness, it can be measured in a variety of clinical settings. Although outpatient studies identified HbA(1c)-screening cutoff values for diabetes and prediabetes, HbA(1c)-screening thresholds have not been determined for acute-care settings. Using follow-up fasting blood glucose (FBG) and the 2-h oral glucose tolerance test (OGTT) as the criterion gold standard, we determined optimal HbA(1c)-screening cutoffs for undiagnosed dysglycemia in the emergency department setting. RESEARCH DESIGN AND METHODS: This was a prospective observational study of adults aged ≥18 years with no known history of hyperglycemia presenting to an emergency department with acute illness. Outpatient FBS and 2-h OGTT were performed after recovery from the acute illness, resulting in diagnostic categorizations of prediabetes, diabetes, and dysglycemia (prediabetes or diabetes). Optimal cutoffs were determined and performance data identified for cut points. RESULTS: A total of 618 patients were included, with a mean age of 49.7 (±14.9) years and mean HbA(1c) of 5.68% (±0.86). On the basis of an OGTT, the prevalence of previously undiagnosed prediabetes and diabetes was 31.9 and 10.5%, respectively. The optimal HbA(1c)-screening cutoff for prediabetes was 5.7% (area under the curve AUC = 0.659, sensitivity = 55%, and specificity = 71%), for dysglycemia 5.8% (AUC = 0.717, sensitivity = 57%, and specificity = 79%), and for diabetes 6.0% (AUC = 0.868, sensitivity = 77%, and specificity = 87%). CONCLUSIONS: We identified HbA(1c) cut points to screen for prediabetes and diabetes in an emergency department adult population. The values coincide with published outpatient study findings and suggest that an emergency department visit provides an opportunity for HbA(1c)-based dysglycemia screening.