Random HbA1c as a screening tool for diabetes mellitus (DM) in the emergency department (ED)

Introduction: The prevalence of diabetes mellitus is rising rapidly although 1/3 of cases remain undiagnosed. The HbA1c was recently recommended as a diagnostic test for diabetes (Diabetes Care, July 2009). Given 120 million annual ED visits in the USA, an ED visit provides further opportunity for identifying undiagnosed diabetics. However, it is not clear whether an ED HbA1c is influenced by stress hyperglycemia of acute illness.

Objective: Determine if an ED HbA1c remains stable over time.

Methods: Adult patients with no known history of DM were tested for HbA1c during their ED and subsequent scheduled follow-up visit within 90 days of the ED visit. The HbA1c differences between the two visits were compared using limits of agreement (LOA) with 95% confidence intervals; predictive values were also calculated using 6.5% to diagnose diabetes.

Results: 525 patients were included (average age 49 years), with 54 out of 525 (10%) having an ED HbA1c ≥ 6.5%. The mean overall ED HbA1c was 5.68% (±0.90) and the follow-up HbA1c 5.67% (±0.92), (difference -0.0099, LOA -0.753, 0.733). Using the follow-up HbA1c as the criterion gold standard, the PPV of an elevated ED HbA1c was 70% (38/54) and the NPV was 99% (466/471). When elevated ED HbA1c values fell < 6.5% on follow-up, most (13/16) still were in an abnormal range (6.0-6.5%).

Conclusion: An elevated HbA1c in the ED usually remains elevated on follow-up evaluation, suggesting this could be used to screen for diabetes in an acute care setting.