Objective: Diabetes is a known risk factor for mortality in Coronavirus disease 2019 (COVID-19) patients . Our objective was to identify prevalence of hyperglycaemia in COVID-19 patients with and without prior diabetes and quantify its association with COVID-19 disease course . Research Design and

Methods: This observational cohort study included all consecutive COVID-19 patients admitted to John H Stroger Jr. Hospital, Chicago, IL from March 15, 2020 to May 3, 2020 and followed till May 15 , 2020 . The primary outcome was hospital mortality, and the studied predictor was hyperglycaemia [any blood glucose ≥ 7.78 mmol/L (140 mg/dL) during hospitalization].

Results: Of the 403 COVID-19 patients studied, 51 (12.7 %) died; 335 (83.1 %) were discharged while 17 (4 %) were still in hospital . Hyperglycaemia occurred in 228 (56.6 %) patients; 83 of these hyperglycaemic patients (36.4 %) had no prior history of diabetes . Compared to the reference group no-diabetes / no-hyperglycaemia patients the no-diabetes / hyperglycaemia patients showed higher mortality [1.8% versus 20.5%, adjusted odds ratio 21.94 (95% confidence interval 4.04-119.0), P <0.001]; improved prediction of death (P = 0.01) and faster progression to death (P <0.01). Hyperglycaemia within the first 24 and 48 hours was also significantly associated with mortality (odds ratio 2.15 and 3.31, respectively).

Conclusions: Hyperglycaemia without prior diabetes was common (20.6% of hospitalized COVID-19 patients) and was associated with an increased risk of and faster progression to death . Development of hyperglycaemia in COVID-19 patients who do not have diabetes is an early indicator of progressive disease.