Pilot bottom-up depleted proteomic analysis of patients from the ManARTS COVID-19 cohort in early stages of the pandemic, for method development of high-throughput proteomics using small volumes of plasma and a 15-minute gradient. Demonstrates proof-of-concept for stratifying patients in an opportunistically collected cohort in a pandemic setting using available hospital data. Convalescent patients were used as an age and sex-matched comparator group against critically ill patients with a current infection.