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.