cfDNA as a surrogate marker for COVID-19 severity in patients with influenza-like symptoms with and without SARS-CoV-2 infections in general practice: a study protocol for a prospective cohort study.

INTRODUCTION: The clinical course of patients with a SARS-CoV-2 (COVID-19) infection varies widely, from symptom-free to severe courses that can lead to death. Laboratory values of SARS-CoV-2 patients such as lymphocyte counts or C-reactive protein (CRP) do not allow a prediction of the actual course of the disease. To identify a possible predictive marker for the differentiation and prognosis of illness with influenza-like symptoms with and without SARS-CoV-2 infections in general practice, we will analyse the concentrations of cell-free DNA (cfDNA) levels, laboratory and clinical parameters, temperature, oxygen saturation, breathing rate and concomitant symptoms in patients with flu-like symptoms with and without a SARS-CoV-2 infection. METHODS AND ANALYSIS: This is a single-centre, two-arm, parallel longitudinal cohort study with a total of 44 patients. 22 patients with flu-like symptoms without a SARS-CoV-2 infection and 22 patients with flu-like symptoms with a SARS-CoV-2 infection will be recruited. The primary objective is to compare cfDNA levels in ambulatory patients in general practice with flu-like symptoms with SARS-CoV-2 infection with those with influenza like symptoms without a SARS-CoV-2 infection during the disease (day 7 and day 14). The secondary objective is to determine whether there is a correlation between cfDNA concentrations on the one hand, and laboratory and clinical parameters on the other hand. cfDNA, differential blood count, high-sensitive CRP and erythrocyte sedimentation rate will be measured in blood samples, concomitant symptoms will be surveyed via a self-assessment questionnaire, and oxygen saturation, breathing rate and examination of the lungs will be reported by treating physicians. ETHICS AND DISSEMINATION: Ethical approval was issued on 1 March 2021 by the Ethics Committee Essen under the number 21-9916-BO. Findings will be published in peer-reviewed open-access journals and presented at national and international conferences. TRIAL REGISTRATION NUMBER: DRKS00024722.

Discrepancy between frequent occurrence of COVID-19-like symptoms and low seroconversion rates among healthcare workers.

During the first wave of the pandemic, we compared the occurrence of subjectively experienced COVID-19-like symptoms and true severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroconversion rates among medical personnel in general practices. This cross-sectional study determined the SARS-CoV-2-specific immunoglobulin G (IgG) antibody status of medical staff from 100 outpatient practices in Germany. Study cohort characteristics and COVID-19-like symptoms were obtained by questionnaires. The initial screening for SARS-CoV-2-recognizing antibodies was performed using a commercial chemiluminescence microparticle immunoassay. Positive results were controlled with another approved test. Samples with discrepant results were subjected to a third IgG-binding assay and a neutralization test. A total of 861 participants were included, 1.7% (n = 15) of whom tested positive for SARS-CoV-specific IgG in the initial screening test. In 46.6% (n = 7) of positive cases, test results were confirmed by an independent test. In the eight samples with discrepant results, neither spike-specific antibodies nor in vitro neutralizing capacity were detectable, resulting in a genuine seroprevalence rate of 0.8%. 794 participants completed the questionnaire. Intriguingly, a total of 53.7% (n = 426) of them stated episodes of COVID-19-like symptoms. Except for smell and taste dysfunction, there were no significant differences between the groups with and without laboratory-confirmed SARS-CoV-2 seroconversion. Our results demonstrated that only 0.8% of participants acquired SARS-CoV-2 even though 53.7% of participants reportedly experienced COVID-19-like symptoms. Thus, even among medical staff, self-diagnosis based on subjectively experienced symptoms does not have a relevant predictive value.