Course of inflammation and infection markers differ in ICU patients with severe COVID-19 under casirivimab- and/or tocilizumab application: an observational study

Background: The outcome and longitudinal course of inflammation and infection markers were unknown in COVID-19 patients on the ICU treated without (N) or with SARS-CoV-2 specific monoclonal antibodies (casirivimab / imdevimab, C) or antibodies against interleukin-6 (IL-6) receptors (tocilizumab, T), solely, or in combination of both (C + T). Methods: In a retrospective observational study, in critically ill N, C, T, C+ T COVID-19 patients admitted to the ICU with the CoV-2 delta-variant between August 2021 and February 2022, 28-day mortality and 30-day time course of infection and inflammation markers were evaluated. Results: Out of 95 patients with COVID-19, 29 patients were not treated (N), 17 with C, 16 with T, 33 with C + T. Mortality rates in N, C, T, and C + T, were 24%, 35%, 56%, and 24%, being higher in T compared to N and C + T (p = 0.05). Prolonged leukocyte, procalcitonin (PCT), C-reactive protein (CRP) and interleukin 6 (IL-6) elevations were detected in nonsurvivors compared to survivors in C + T within the first two weeks, IL-6 in the first days in T. In N, higher PCT, CRP, IL-6 and ferritin occured in nonsurvivors in the first days. Conclusion: Sporadically measured IL-6 and CRP in T is less useful. Longlasting IL-6 receptor blockade may be deleterious in COVID-19. High IL-6 may hint at poor prognosis within the first days in T, leukocytes, PCT, CRP and IL-6 in the first two weeks in C + T, and PCT, CRP, IL-6 and ferritin within the first days in N. Trial registration: ClinicalTrials.gov Identifier: NCT06233357, retrospectively registered, release date: January 31, 2024.