Issue 151 Item 6 HbA1c Detects Diabetes

HbA1c is a useful marker for case finding of diabetes patients. ” HbA1c level is considered an important monitoring tool in treating patients with diabetes, but it is not currently recommended for screening or for the diagnosis of diabetes,” write Laura S. Greci, MD, MPH, from Yale University School of Medicine in Derby, Connecticut, and colleagues. “To our knowledge, this is the first study reporting on the role of HbA1c level for diabetes case finding in hospitalized patients with hyperglycemia. This situation may provide a golden opportunity to locate, educate, and begin treating the large number of undiagnosed patients with diabetes.”

From March 20 to July 31, 2000, 508 patients admitted through the emergency department of a single hospital were tested for random hyperglycemia, defined as plasma glucose greater than 125 mg/dL.

Of 50 patients (9.8%) with hyperglycemia but without corticosteroid use or history of diabetes, 35 patients (70%) completed the study, and 21 patients (60%) were diagnosed with diabetes based on testing of fasting plasma glucose while hospitalized.

Mean HbA1c levels were higher in subjects with diabetes than in subjects without diabetes (6.8 ± 0.4 vs. 5.3 ± 0.1%; P = .002). Using a cutoff of greater than 6.0%, the HbA1c level was 100% specific (14 of 14 patients) and 57% sensitive (12 of 21 patients) for the diagnosis of diabetes. Using a lower cutoff value of HbA1c at 5.2%, specificity was 50% (10 of 21 patients) and sensitivity was 100% (7 of 14 patients).

“In acutely ill patients with random hyperglycemia at hospital admission, an HbA1c) level greater than 6.0% reliably diagnoses diabetes, and an HbA1c level less than 5.2% reliably excludes it (paralleling the operating characteristics of the standard fasting glucose measurements),” the authors write.

Study limitations include small sample size, older patient population, and possible effect of acute medical condition on the gold standard of testing fasting plasma glucose while hospitalized. The authors warn that the clinical algorithm in this study needs to be validated in prospective studies on different populations.

“Issues of cost, labor, laboratory use, and patient convenience and compliance will also need to be factored in to the best approach in hospitalized patients,” they write. “This quicker diagnosis of diabetes with the HbA1c level can also translate into an early inpatient mobilization of diabetes support services (e.g., nutrition and education), treatment, and even early medication response.”

Diabetes Care. 2003;26:1064-1068

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DID YOU KNOW: Hypertensive patients not conventionally deemed dyslipidemic (normal to mildly elevated cholesterol) who take atorvastatin had 36% fewer fatal coronary events and nonfatal MI than patients treated with placebo.