Abstract: Journal of Clinical Medicine Article Incidence of COVID-19 Hospitalisation in Patients with Systemic Lupus Erythematosus: A Nationwide Cohort Study from Denmark René Cordtz 1,2, *,† , Salome Kristensen 1,3,† , Louise Plank Holm Dalgaard 1 , Rasmus Westermann 1 , Kirsten Duch 1,4 , Jesper Lindhardsen 5 , Christian Torp-Pedersen 6,7 and Lene Dreyer 1,2,3 1 2 3 4 5 6



 7 * † Department of Rheumatology, Aalborg University Hospital, 9000 Aalborg, Denmark; sakr@rn.dk (S.K.); louise.dalgaard@rn.dk (L.P.H.D.); raw@rn.dk (R.W.); k.duch@rn.dk (K.D.); l.dreyer@rn.dk (L.D.) Department of Rheumatology, Center for Rheumatology and Spine Diseases, Gentofte Hospital, 2900 Hellerup, Denmark Department of Clinical Medicine, Aalborg University, 9000 Aalborg, Denmark Unit of Clinical Biostatistics, Aalborg University Hospital, 9000 Aalborg, Denmark Lupus and Vasculitis Clinic, Center for Rheumatology and Spine Diseases, Rigshospitalet, 2100 Copenhagen, Denmark; jesper.lindhardsen@regionh.dk Department of Cardiology, Nordsjællands Hospital, 3400 Hillerod, Denmark; christian.torp-pedersen.01@regionh.dk Department of Public Health, University of Copenhagen, 1014 Copenhagen, Denmark Correspondence: r.cordtz@rn.dk Shared first authorship/contributed equally. Citation: Cordtz, R.; Kristensen, S.; Dalgaard, L.P.H.; Westermann, R.; Duch, K.; Lindhardsen, J.; Torp-Pedersen, C.; Dreyer, L. Incidence of COVID-19 Hospitalisation in Patients with Systemic Lupus Erythematosus: A Nationwide Cohort Study from Denmark. J. Clin. Med. 2021, 10, 3842. https://doi.org/10.3390/ jcm10173842 Academic Editors: Christopher Sjöwall and Ioannis Parodis Received: 30 July 2021 Accepted: 23 August 2021 Published: 27 August 2021 Abstract: Background: Patients with systemic lupus erythematosus (SLE) have an increased risk of infections due to impaired immune functions, disease activity, and treatment. This study investigated the impact of having SLE on the incidence of hospitalisation with COVID-19 infection. Methods: This was a nationwide cohort study from Denmark between 1 March 2020 to 2 February 2021, based on the linkage of several nationwide registers. The adjusted incidence of COVID-19 hospitalisation was estimated for patients with SLE compared with the general population in Cox-regression models. Among SLE patients, the hazard ratio (HR) for hospitalisation was analysed as nested case-control study. Results: Sixteen of the 2533 SLE patients were hospitalised with COVID-19 infection. The age-sex adjusted rate per 1000 person years was 6.16 (95% CI 3.76–10.08) in SLE patients, and the corresponding hazard ratio was 2.54 (95% CI 1.55–4.16) compared with the matched general population group after adjustment for comorbidities. Among SLE patients, hydroxychloroquine treatment was associated with a HR for hospitalisation of 0.61 (95% CI 0.19–1.88), and 1.06 (95% CI 0.3–3.72) for glucocorticoid treatment. Conclusion: Patients with SLE were at increased risk of hospitalisation with COVID-19. Keywords: systemic lupus erythematosus; COVID-19; hydroxychloroquine; glucocorticoids Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1...