* Includes chronic obstructive pulmonary disease, asthma, and pulmonary fibrosis

* Includes chronic obstructive pulmonary disease, asthma, and pulmonary fibrosis. == Table 2. assay and an in-house developed Luminex immunoassay. Kinetics of the serological response and correlation between the antibody titers and outcome were assessed. Among the 70 patients enrolled in the study, 22 required invasive ventilation, 29 required non-invasive ventilation or oxygen supplementation, and 19 did not require any oxygen supplementation. Median duration of symptoms upon admission for the three groups were 13, 8, and 9 days, respectively. Antibody titers gradually increased for up to 3 weeks since the onset of symptoms for patients requiring oxygen supplementation with significantly higher antibody titers for patients requiring invasive ventilation. Antibody titers on admission were also significantly higher in severely ill patients and serology performed well in predicting the necessity of invasive ventilation (AUC: 0.79, 95% CI: 0.670.9). Serology testing at admission may be a good indicator to identify severe COVID-19 patients who will require invasive mechanical ventilation. Keywords:serology, antibody response, SARS-CoV-2, COVID-19, outcome, disease severity == 1. Introduction == Coronavirus disease 2019 (COVID-19) due to YM90K hydrochloride SARS-CoV-2 is associated with a wide spectrum of symptoms, ranging from asymptomatic infection to acute respiratory distress syndrome [1,2,3,4]. COVID-19 is often biphasic, with acute respiratory distress syndrome developing after a few days of initially mild symptoms (usually above one week) in some patients as a consequence of pro-inflammatory cytokine release [5]. This detrimental role of the immune response has led to the hypothesis that the antibody-mediated immune response could contribute to the disease severity [6,7,8]. Early assessment of the disease severity and prediction of outcome might help physicians to optimize the patients medical care and resource management [9,10,11]. Some prediction tools have been developed based on epidemiologic, clinical, or laboratory features [12] but their performances have been limited and most of them have not been prospectively evaluated [13]. The importance of the anti-SARS-CoV-2 antibody response has been suggested as an indicator of the degree of disease severity. However, reports that relate antibody titers to disease severity showed discordant results [5,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29]. TSPAN5 In order to evaluate the kinetics of the anti-SARS-CoV-2 humoral immune response and its role as a prognostic factor, we conducted a prospective observational study in hospitalized patients with serial monitoring of their immunoglobulin G (IgG) response to SARS-CoV-2 measured by two different methods during the course of infection. Our aim was to assess the role of serology as a pragmatic stratification tool to evaluate the YM90K hydrochloride patients prognosis upon hospital admission. == 2. Materials and Methods == == 2.1. Study Design and Participants == This was a prospective observational study conducted at Lausanne University Hospital (CHUV) between 1 April 2020 and 1 August 2020. All hospitalized patients with acute respiratory symptoms and COVID-19 infection confirmed by a positive nucleic acid amplification test (NAAT) for SARS-CoV-2 in a nasopharyngeal swab or any other respiratory specimen were included if the hospital stay was anticipated to last for more than 48 h and provided that informed consent was obtained. Exclusion criteria were: (1) nosocomial acquisition of COVID-19 and (2) patients with documented concomitant active infection at the time of COVID-19 diagnosis. Patients were classified according to the severity of COVID-19 considering the entire hospital stay (i.e., highest degree of severity) using a modified ordinal scale as recommended by the World Health Organization research and development (WHO R&D) Blueprint group [30,31] as follows: (1) No oxygen therapy; (2) oxygen by masks or nasal prongs; (3) non-invasive ventilation or high-flow oxygen; (4) mechanical ventilation; (5) mechanical ventilation and additional organ support (vasopressors, renal replacement therapy or extracorporeal membrane oxygenation); and (6) death. Included patients were subsequently divided into three groups: mild YM90K hydrochloride cases (category 1), moderate cases (categories 2 and 3), and severe cases (categories 4 to 6 6). Demographic, clinical, and laboratory data were collected from the electronic health records from our hospital. The timing of COVID-19 was assessed from the day of the start of first symptoms (i.e., fever or any flu-like or respiratory symptoms) as reported by.