Utility of HbA1c Levels for Diabetes Case Finding in Hospitalized Patients With Hyperglycemia

Abstract

OBJECTIVE—We evaluated the role of a single measurement of HbA1c in a diabetes case finding in hospitalized patients with random hyperglycemia at admission. RESEARCH DESIGN AND METHODS—From 20 March to 31 July 2000, 508 patients admitted through the emergency department of one hospital were tested for random hyperglycemia (plasma glucose [PG] >125 mg/dl). Consenting patients with hyperglycemia (without preexisting diabetes or on corticosteroids) underwent testing for HbA1c levels, two fasting PG levels, and an outpatient oral glucose tolerance test (OGTT) if necessary. RESULTS—Of the patients, 50 (9.8%) met the inclusion criteria. Of these, 70% (n = 35) completed the study, and 60% (n = 21) were diagnosed with diabetes. Patients with diabetes had higher HbA1c levels than subjects without diabetes (6.8 ± 0.4 vs. 5.3 ± 0.1%, P = 0.002). An HbA1c level >6.0% was 100% specific (14/14) and 57% sensitive (12/21) for the diagnosis of diabetes. When a lower cutoff value of HbA1c at 5.2% was used, specificity was 50% (10/21) and sensitivity was 100% (7/14). CONCLUSIONS—In acutely ill patients with random hyperglycemia at hospital admission, an HbA1c >6.0% reliably diagnoses diabetes, and an HbA1c level <5.2% reliably excludes it (paralleling the operating characteristics of the standard fasting glucose measurements); however, the rapidity of the HbA1c level can be useful for diabetes case finding and treatment initiation early in the hospital course.