A prospective study of the impact of glycaemic status on clinical outcomes and anti-SARS-CoV-2 antibody responses among patients with predominantly non-severe COVID-19

OBJECTIVE: We aimed to evaluate the impact of glycaemic status on clinical outcomes and anti-SARS-CoV-2 antibody (Ab) response among patients with predominantly non-severe COVID-19, highly relevant to the current COVID-19 vaccination programme. METHODS: We included consecutive adults admitted to Queen Mary Hospital for COVID-19 from July 2020 to May 2021. Glycaemic status was defined by HbA1c on admission: normoglycaemia (<5.7%), prediabetes (5.7-6.4%) and diabetes (≥6.5% or known diabetes). Clinical deterioration was defined by radiological progression, new oxygen requirement, intensive care unit admission, or death. COVID-19 survivors had Ab measurements at 1-month, 2-month, 3- month and 6-month post-discharge, with a live SARS-CoV-2-based microneutralization assay which correlated well with anti-SARS-CoV-2 receptor binding domain IgG (≥1:20 defined as positive). RESULTS: Among 605 patients (age 50.2 - 17.1 years;45.1% men;96.9% non-severe COVID-19), 325 had normoglycaemia, 185 had prediabetes and 95 had diabetes. 74 had clinical deterioration (12.2%): 16 required intensive care and 4 died. Clinical deterioration was more likely with worse glycaemic status (P < 0.001) and higher HbA1c (OR 1.403, P < 0.001). Older age (P < 0.001), higher viral loads (P < 0.001), higher C-reactive protein (CRP) (P < 0.001) and symptomatic presentation (P = 0.008), but not glycaemic status/HbA1c, independently predicted clinical deterioration. 314 patients had Ab measured upon follow-up (1-month: 295;2-month: 227;3-month: 207;6-month: 122). Ab titres were comparable across glycaemic status throughout follow-up period. CRP (P = 0.003), but not glycaemic status/HbA1c, was the only positive independent determinant of Ab levels. Rate of decline of Ab titre was comparable across glycaemic status, and did not correlate with HbA1c. Furthermore, most patients remained Ab-positive throughout follow-up (1-month: 94.9%, 2-month: 93.8%, 3-month: 87.4%, 6-month 80.3%), similar across glycaemic status. CONCLUSION: Worse glycaemic status was associated with a higher chance of clinical deterioration in COVID-19, contributed by older age, more severe inflammation and higher viral loads. Importantly, glycaemic status did not adversely influence the Ab response.