Methods
We undertook a detailed literature search with full assessment of relevant articles by searching the following databases: Google Scholar, Medline and Embase. We used Medical Subject Heading (MeSH) terms: diabetes mellitus, COVID-19, infection, comorbidity, patients’ characteristics, risk factors, adverse outcomes, prevalence, mortality, predictors, disease progression, disease severity and glycaemic control. We searched articles for three categories of data:
1. Articles that reported diabetes as comorbidity in patients with COVID-19.
2. Articles that reported diabetes as a contributing factor to clinical outcomes.
3. Articles that specifically reported the characteristics of patients with diabetes affected by COVID-19.
Articles were reviewed for relevance by abstract. A manual search of citations in retrieved articles was performed in addition to the electronic literature search. We limited our selection to studies published in English language and reported clear outcomes. For data extractions, all articles derived from the search enquiry were independently examined by the authors and data was extracted in a standardised format, which included study design, population studied and main findings.