Does the HbA_1c Criterion for Prediabetes Predict Incident Diabetes?

The American Diabetes Association recently added a new criterion for diagnosis of prediabetes — glycosylated hemoglobin (HbA_1c) level of 5.7% to 6.4%. To evaluate this new criterion, Japanese investigators studied 6241 people who had five or six consecutive annual health examinations that included measurements of fasting glucose and HbA_1c levels.

At their baseline examinations, 2092 patients were identified as prediabetic: 60% by impaired fasting glucose (IFG; 100–125 mg/dL) alone, 20% by HbA_1c alone, and 20% by both tests. During a mean 4.7-year follow-up, 338 patients progressed to diabetes, of whom 292 (86%) had been identified as prediabetic at baseline: 32% by IFG alone, 9% by HbA_1c alone, and 46% by both tests. Both IFG alone and HbA_1c…