Objective
To establish the demographic characteristics, laboratory findings and clinical outcomes in patients with autoimmune disease (AD) in comparison to a propensity matched cohort of patients without AD admitted with COVID-19 to hospitals in the UK.

Methods
This is a multicentre observational study across 26 NHS Trusts. Data were collected both retrospectively and prospectively using a pre-designed standardised case record form. Adult patients (≥18 years) admitted between 1st of April 2020 and 31 July 2020 were included.

Results
Overall, 6288 patients were included to the study. Of these, 394 patients had AD prior to admission with COVID-19. Of 394 patients, 80 patients with systemic lupus erythematosus, rheumatoid arthritis or antiphospholipid syndrome were classified as severe rheumatologic AD. A higher proportion of those with AD had anaemia: 240(60.91%) vs 206(52.28%), p= 0.015, raised LDH 150(38.08%) vs 43(10.92%), p< 0.001 and raised creatinine 122(30.96%) vs 86(21.83%), p= 0.01 respectively. A significantly higher proportion of patients with severe rheumatologic AD had raised CRP : 77(96.25%) vs 70(87.5%), p= 0.044 and LDH 20(25%) vs 6(7.5%), p= 0.021. Patients with severe rheumatologic AD had significantly higher mortality [32/80(40%)] compared with propensity matched cohort of patients without AD [20/80(25%)], p= 0.043. However, there was no difference in 180-day mortality between propensity matched cohorts of patients with or without AD in general, p= 0.47.

Conclusions
Patients with severe rheumatologic AD had significantly higher mortality. Anaemia, renal impairment and raised LDH were more frequent in patients with any AD whilst raised CRP and LDH were more frequent in patients with severe rheumatologic AD both of which have been shown to associate with increased mortality in patients with COVID-19.