2.1. Data Collection
The data for this study was retrospectively retrieved from the SARSTer, a nationwide database managed by the Polish Association of Epidemiologists and Infectiologists, and used to collect observational data on patients hospitalized since the beginning of the COVID-19 pandemic. The project involves 44 Polish centers located in different regions of Poland.
The studied population was selected from the database of hospitalized adult patients infected with SARS-CoV-2. It included 1822 patients hospitalized during the following pandemic periods: (i) from 1 August 2021 to 31 December 2021 (defined as Delta wave), and (ii) from 1 January 2022 to 30 April 2022 (defined as Omicron wave). Of these, 762 were treated with remdesivir (RDV), and the control group (NO AVT) included 1060 patients (680 during the Delta wave and 380 during the Omicron wave) who were not treated with RDV and any other antiviral drug and were matched by age, sex, BMI, presence of any comorbidity, and SpO2 at admission. According to the product characteristics and recommendations, RDV was administered intravenously once daily for 5-10 days, with a loading dose of 200 mg on day 1, followed by a maintenance dose of 100 mg to 762 patients (490 during the Delta wave and 272 during the Omicron wave) 19,20.
Similarly to previous research from SARSTer database21,22, two periods of variants dominance were established based on sequences submitted by Polish laboratories according to the Global Initiative on Sharing All Influenza Data (GISAID), the most reliable database on SARS-CoV-2 variants prevalence in different regions of the world 23. Infection of SARS-CoV-2 was diagnosed based on a positive polymerase chain reaction or antigen test result, while management and treatment followed current national recommendations for COVID-1919,20.
The patients’ demographic data included: age, sex, BMI, and comorbidities. The laboratory data assessed at the baseline included: C-reactive protein (CRP), procalcitonin (PCT), white blood cell (WBC) count, absolute number of lymphocytes (ALC), neutrophils (ANC) and platelets (PLT), interleukin-6 (IL-6), D-dimer and alanine aminotransferase (ALT) activity. Upon admission to the hospital, patients were assigned to one of the categories based on the presence of symptoms and oxygen saturation (SpO2) when breathing room air: (1) asymptomatic, (2) stable symptomatic with SpO2>95, (3) unstable symptomatic with SpO2 91-95%, (4) unstable symptomatic with SpO2≤90, and acute respiratory distress syndrome (ARDS). The clinical course of the disease was assessed on admission to the hospital, and then after 7, 14, 21, and 28 days using an ordinal scale based on WHO recommendations, it was modified to the 8-point version to match the specificity of the Polish healthcare system and used in previous SARSTer research 24,25. The score was defined as follows: (1) not hospitalized, no activity restrictions; (2) not hospitalized, no activity restrictions and/or not requiring oxygen supplementation at home; (3) hospitalized, and not requiring oxygen supplementation and not requiring medical care; (4) hospitalized, not requiring oxygen supplementation, but requiring medical care; (5) hospitalized, requiring normal oxygen supplementation; (6) hospitalized, requiring non-invasive ventilation with high-flow oxygen equipment; (7) hospitalized, for invasive mechanical ventilation or extracorporeal membrane oxygenation; (8) death. The collected data also included the use of medications during hospitalization, such as antivirals, immunomodulators, antibiotics, and low-molecular-weight heparin. Information on vaccination status and history of previous infections with SARS-CoV-2 was unavailable in the database.
Study endpoints were defined as the need for oxygen therapy, the need for mechanical ventilation, and 28-day mortality and were compared between studied cohorts.
The study was conducted according to the guidelines of the Declaration of Helsinki. The SARSTer study had the approval of the Ethical Committee of the Medical University of Białystok (APK.002.303.2020). Patient consent was waived due to the retrospective design of the study.