The present study provides evidence that the HbA1c test can be an effective means of identifying patients with NKHD who have hyperglycemia and occult chronic disease. This study showed that more than three-fourths of patients with NKHD had chronic dysglycemia (as determined by HbA1c values), with almost 60% meeting criteria for the diagnosis of diabetes. Study patients with NKHD were 5 times more likely to leave the hospital with a diabetes diagnosis when HbA1c levels were measured than when they were not measured.
The 50 patients with NKHD had a 50% longer mean (SD) hospital stay compared with the 298 patients with known diabetes (4.2 [3.1] vs 2.6 [1.8] days). This finding is consistent with that of Umpierrez et al
2 and other studies
3,16,23 that reported increased hospital stays (9.0 vs 5.5 days) in patients with newly recognized hyperglycemia vs patients with known diabetes. In a study by Sleiman et al,
24 for every 1% increase in HbA
1c, patient readmission rates nearly doubled.
While the efficacy of HbA
1c testing in recognizing occult disease in patients with NKHD was the focus of this study, our findings shed light on the opportunity to identify poor long-term glucose control in patients already being treated for disease. A large majority (298 [86%]) of hyperglycemic patients in this study had known diabetes, but an HbA
1c test was not ordered for 101 (29%) of these patients. This observation suggests that even for patients with known diabetes, the HbA
1c test is often underused. Potential reasons for this situation may include a lack of protocol to respond to an elevated glucose or HbA
1c level, a recent outpatient record of the test, costs associated with ordering additional diagnostic tests, clinicians—especially new ones—not being abreast with current standards of care, or lapses in the admissions process from emergent care to the inpatient setting. Knowledge of an elevated HbA
1c level provides an opportunity to adjust therapy. For example, Dungan et al
25 showed that patients with an HbA
1c level greater than 8% and inpatient intensification of their treatment had a 33% reduction in readmission rate.
Any episode of dysglycemia represents a failure of the body’s ability to maintain euglycemia. One may argue that episodes of hyperglycemia are themselves indicators of disease, notwithstanding other factors. Thus, transient hyperglycemia may exist on a continuum with, rather than distinct from, diabetes. Failure to properly evaluate hyperglycemia is an issue regardless of the context in which it happens—whether clinicians explain the elevated glucose with circumstance or ignore it. In a previous study, only 13% of hyperglycemic inpatients were directed to begin a diabetic diet regimen, 2% were given oral hypoglycemic agents, and 6% received scheduled insulin.
3 If hyperglycemia is not explained in the emergency department or hospital, it will likely persist.
The implementation of reflex HbA
1c testing provides an assurance that those with an isolated episode of hyperglycemia are differentiated from those with chronic disease, and it provides a mechanism to stem clinical inertia in diabetes care. The present study supports the need for standardized protocols that include reflex administration of an HbA
1c test. Establishing hospital protocols that include an HbA
1c test in response to hyperglycemia will ensure the early identification of new disease and initiation of patient-specific therapy.
26 Moreover, this test will allow physicians to adjust existing therapeutic regimens for better control of blood glucose. Recognition of chronic dysglycemia can improve short-term and long-term outcomes for these patients, including reduced morbidity, mortality, and surgical site infections.
3,23,25 Use of HbA
1c level to assess all patients with hyperglycemia, regardless of diabetes history, will have a positive impact on health care quality and cost.
20,27 The test can be done at any time, patients are not required to be fasting, and the results are usually obtained within hours.
The present study had a number of limitations. The data were collected retrospectively from a single center. Hence, a large multicenter study will be warranted to determine the real efficacy of the HbA1c test in inpatients with hyperglycemia and NKHD. Lists were generated from 2 different hospital record systems that did not yield identical results. Although the research team tracked individual admissions and cross-referenced them, some records may have been missed. The number of patients with NKHD was quite small, which reflects the large number of patients with known diabetes (85%) and the limited total number of admissions during the study period. Of special note is the rural geographic location and limited resources of the hospital involved in the study. Patients are often transferred to larger urban institutions, resulting in shortened in-house management. Nonetheless, the results of this study are still provocative to inpatient diabetes care in the “real world.” The diagnosis of diabetes in 17 patients rather than all 18 patients with high HbA1c levels reflects a missed opportunity—at least in documentation—of identifying diabetes in 1 patient. Furthermore, 2 people with NKHD were discharged with a diagnosis of diabetes but without clear HbA1c confirmation.
The HbA
1c test is not perfect, especially because of the existence of hemoglobin variants.
28 Any alteration of red blood cells arising from disease or procedures such as anemia, hemoglobinopathies, or blood transfusion may affect test results. In the 2015 American Diabetes Association Standards of Care,
15 blood loss, hemolysis, blood transfusion, erythropoietin therapy, and iron deficiency were noted as conditions that could compromise the accuracy of HbA
1c test results. In addition, there may be little benefit in obtaining HbA
1c values in patients who have had the test in the past 3 months or in those with known hemoglobinopathies. Furthermore, it may be prudent to only select patients who have more than 1 abnormal glucose reading before ordering an HbA
1c test. However, it is well established that hyperglycemia goes unnoticed and is undertreated for many hospitalized patients despite the evidence that shows undiagnosed diabetes contributes to higher mortality and longer length of stays. The small cost for an HbA
1c test can be easily recouped and the rather high disease-related expenses can be avoided.
It is also important to note that a normal HbA1c level should not overrule acute hyperglycemia in the hospital. Even with a normal HbA1c level, acute hyperglycemia must be treated promptly to reduce the risk of the associated adverse outcomes.