Hemoglobin A1c testing alone does not sufficiently identify patients with prediabetes.

Whether hemoglobin A(1c) (HbA(1c)) values are suitable for diagnosing diabetes has been debated. We sought to assess the prevalence of elevated HbA(1c) levels in a prediabetes patient population. Oral glucose tolerance tests and HbA(1c) levels were analyzed for patients entering a diabetes prevention program between January 1, 2007, and September 13, 2009. We calculated the percentage of patients with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) who had HbA(1c) values in the 6.0% to 6.4% range or in the 5.7% to 6.4% range. The mean age of the 242 patients was 62 years; 64.0% were women, and 88.0% were white. Isolated IFG was detected in about 56.2% of patients and combined IFG and IGT in about 37.2%. Only 28.5% of patients had HbA(1c) values in the 6.0% to 6.4% range, whereas 65.3% had values in the 5.7% to 6.4% range. Our data suggest that reliance on HbA(1c) testing alone to identify candidates for a diabetes prevention program would miss a substantial number of eligible patients.