Hyperglycemia and diabetes mellitus are very common in hospitalized patients. Although more data are available on the prevalence of this problem and on how to manage it in the intensive care unit (ICU) than on regular hospital floors, the situation is changing. Information is emerging on the prevalence and impact of hyperglycemia and diabetes in the non-ICU setting, which is the focus of this paper.
HYPERGLYCEMIA IS COMMON AND PREDICTS POOR OUTCOMES
Cook et al,1 in a survey of 126 US hospitals, found that the prevalence of hyperglycemia (blood glucose > 180 mg/dL) was 46% in the ICU and 32% in regular wards.
Kosiborod et al2 reported that hyperglycemia (blood glucose > 140 mg/dL) was present in 78% of diabetic patients hospitalized with acute coronary syndrome and 26% of similar hospitalized nondiabetic patients.
Hyperglycemia is a common comorbidity in medical-surgical patients in community hospitals. Our group3 found that, in our hospital, 62% of patients were normoglycemic (ie, had a fasting blood glucose < 126 mg/dL or a random blood glucose < 200 mg/dL on two occasions), 26% had known diabetes, and 12% had new hyperglycemia. Further, new hyperglycemia was associated with a higher in-hospital death rate than the other two conditions.
Failure to identify diabetes is a predictor of rehospitalization. Robbins and Webb4 reported that 30.6% of those who had diabetes that was missed during hospitalization were readmitted within 30 days, compared with 9.4% of patients with diabetes first diagnosed during hospitalization.
WHAT DIAGNOSTIC CRITERIA SHOULD WE USE?
Blood glucose greater than 140 mg/dL
A consensus statement from the American Association of Clinical Endocrinologists (ACE) and the American Diabetes Association (ADA)5 defines in-hospital hyperglycemia as a blood glucose level greater than 140 mg/dL on admission or in the hospital. If the blood glucose is higher than this, the question arises as to whether the patient has preexisting diabetes or has stress hyperglycemia.
Hemoglobin A1c of 6.5% or higher
In view of the uncertainty as to whether a patient with an elevated blood glucose level has preexisting diabetes or stress hyperglycemia, upcoming guidelines will recommend measuring the hemoglobin A1c level if the blood glucose level is higher than 140 mg/dL.
A patient with an elevated blood glucose level (>140 mg/dL) whose hemoglobin A1c level is 6.5% or higher can be identified as having diabetes that preceded the hospitalization. Hemoglobin A1c testing can also be useful to assess glycemic control before admission and in designing an optional regimen at the time of discharge. In patients with newly recognized hyperglycemia, a hemoglobin A1c measurement can help differentiate patients with previously undiagnosed diabetes from those with stress-induced hyperglycemia.
Clinicians should keep in mind that a hemoglobin A1c cutoff of 6.5% identifies fewer cases of undiagnosed diabetes than does a high fasting glucose concentration, and that a level less than 6.5% does not rule out the diagnosis of diabetes. Several epidemiologic studies6 have reported a low sensitivity (44% to 66%) but a high specificity (76% to 99%) for hemoglobin A1c values higher than 6.5% in an outpatient population. The high specificity therefore supports the use of hemoglobin A1c to confirm the diagnosis of diabetes in patients with hyperglycemia, but the low sensitivity indicates that this test should not be used for universal screening in the hospital.
Many factors can influence the hemoglobin A1c level, such as anemia, iron deficiency, blood transfusions, hemolytic anemia, and renal failure.
Until now, if patients had hyperglycemia but no prior diagnosis of diabetes, the recommendation was for an oral 2-hour glucose tolerance test shortly after discharge to confirm the diagnosis of diabetes. Norhammar et al7 performed oral glucose tolerance tests in patients admitted with acute myocardial infarction, and Matz et al8 performed glucose tolerance tests in patients with acute stroke. They found that impaired glucose tolerance and undiagnosed type 2 diabetes were very common in these two groups. However, physicians rarely order oral glucose tolerance tests. We believe that hemoglobin A1c will be a better tool than an oral glucose tolerance test to confirm diabetes in hyperglycemic patients in the hospital setting.
