What is the role of admission <scp>HbA1c</scp> in managing <scp>COVID</scp>‐19 patients?

Abstract

Some recent articles published in the Journal of Diabetes have raised concerns about the importance of checking glycosylated hemoglobin (HbA1c) upon hospital admission for coronavirus disease 2019 (COVID-19) patients.1-3 It is now undoubtedly clear that absolute hyperglycemia at the time of admission increases the risk of severe outcomes of COVID-19, independent of prior diabetes status,4, 5 and tight glycemic control improves the prognosis of these patients significantly.4, 5 However, the role of admission HbA1c, which reflects average glycemia over the preceding 2 to 3 months, in the management of COVID-19 patients remains uncertain. Some studies have shown a significant association between admission HbA1c and disease progression or mortality in COVID-19 patients, whereas a few others did not (Table 1). While the reasons for this discrepancy are not clear, most of these studies are constrained by a small number of patients,6, 7 a large proportion of missing HbA1c data,8 and inadequate adjustment of potential confounders.8, 9 Previous research has shown that background glycemia mediates the association between admission glucose and outcomes in patients with a variety of medical conditions.10-12 Thus, correcting admission glucose levels for background glycemia estimated by HbA1c, the so-called relative hyperglycemia predicts outcomes in acute health conditions better than absolute hyperglycemia,10, 13 albeit not yet proven in the COVID-19 context. Mortality Markers of inflammation and hypercoagulability, and oxygen saturation Higher mortality rate with increasing HbA1c levels: 9.8% in group A (n = 41, no diabetes and HbA1c ≤6.0%), 11.4% in group B (n = 44, no diabetes and HbA1c >6.0- < 6.5%), and 27.7% in group C (n = 47, diabetes and/or HbA1c ≥6.5%), P = .04 Negative correlation between HbA1c and SaO2 (r = −0.22, P = .01). Positive correlation between HbA1c and ferritin (r = 0.24, P = .01), CRP (r = 0.22, P = .01), fibrinogen (r = 0.27, P < .01), and ESR (r = 0.27, P < .01) Invasive mechanical ventilation or death within 7 days of admission Since HbA1c is relatively unaffected by the stress of acute illness,14 it may help identify newly diagnosed diabetes cases in COVID-19 patients. Newly diagnosed diabetes (new onset or previously undiagnosed) is now increasingly recognized as a common phenomenon in COVID-19 patients.15, 16 More importantly, COVID-19 patients with newly diagnosed diabetes appear to be at a greater risk for poor prognosis not only compared with those without diabetes but also individuals with known diabetes.17-19 To summarize, admission blood glucose is certainly a key biomarker to risk stratify and guide the clinical management of COVID-19 patients, with or without known diabetes. Thus, it is essential that all COVID-19 patients be screened for absolute hyperglycemia upon admission so that early and appropriate treatment can be initiated if required. While the role of admission HbA1c as a marker of COVID-19 severity is yet to be fully established, HbA1c assists in identifying patients with newly diagnosed diabetes.15, 20 These patients are a high-risk group and should be closely monitored for the emergence of cardiometabolic disorders in the long term.16 No funding received. None declared.

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