Antibody detection is essential to establish exposure, infection, and immunity to SARS-CoV-2, as well as to perform epidemiological studies. The worldwide urge for new diagnostic tools to control the pandemic has led to a quick incorporation in clinical practice of the recently developed serological assays. However, as only few comparative studies have been published, there is a lack of data about the diagnostic accuracy of currently available assays. We evaluated the diagnostic accuracy to detect Ig G, Ig M+A, and/or IgA anti SARS-CoV-2 of 10 different assays: lateral flow card immunoassays, 4 enzyme-linked immunosorbent assay (ELISA), and 3 chemiluminescent particle immunoassays (CMIA). Using reverse transcriptase polymerase chain reaction (RT-PCR) for COVID-19 as gold standard, sensitivity, specificity, PPV, and NPV were determined. Each assay was tested in 2 groups, namely, positive control, formed by 50 sera from 50 patients with SARS-CoV-2 pneumonia with positive RT-PCR; and negative control, formed by 50 sera from 50 patients with respiratory infection non-COVID-19. Sensitivity range of the 10 assays evaluated for patients with positive COVID-19 RT-PCR was 40-77% (65-81% considering IgG plus IgM). Specificity ranged 83-100%. VPP and VPN were respectively 81-100% and 61.6-81%. Among the lateral flow immunoassays, the highest sensitivity and specificity results were found in Wondfo® SARS-CoV-2 Antibody Test. ELISA IgG and IgA from EUROIMMUN® were the most sensitive ELISA. However, poor results were obtained for isolated detection of IgG. We found similar sensitivity for IgG with SARS-CoV-2 for Architect by Abbott® and ELISA by Vircell®. Results obtained varied widely among the assays evaluated. Due to a better specificity, overall diagnostic accuracy of the assays evaluated was higher in case of positive result. On the other side, lack of antibody detection should be taken with care because of the low sensitivity described. Highest diagnostic accuracy was obtained with ELISA and CMIAs, but they last much longer.

Background Early Kinetics of SARS‐CoV‐2 viral load (VL) in plasma determined by quantitative RT‐PCR was evaluated as a predictor of poor clinical outcome in a prospective study and assessed in a retrospective validation cohort. Methods Prospective observational single‐centre study including consecutive adult patients hospitalised with COVID‐19 between November 2020 and January 2021. Serial plasma samples were obtained until discharge. Quantitative RT‐PCR was performed to assess SARS‐CoV‐2 VL. The main outcomes were in‐hospital mortality, admission to the Intensive Care Unit (ICU) and their combination (Poor Outcome). Relevant Viremia (RV), established in the prospective study, was assessed in a retrospective cohort including hospitalised COVID‐19 patients from April 2021‐May 2022, in which plasma samples were collected according to clinical criteria. Results Prospective cohort: 57 patients were included. RV was defined as at least a two‐fold increase in VL within ≤2 days or a VL>300 copies/mL, in the first week. Patients with RV (N=14; 24.6%) were more likely to die than those without RV (35.7% vs 0%), needed ICU admission (57% vs 0%) or had Poor Outcome (71.4% vs 0%), (p<0.001 for the three variables) Retrospective cohort: 326 patients were included, 18.7% presented RV. Patients with RV compared with patients without RV had higher rates of ICU‐admission [OR 5.6 (95%CI,2.1‐15.1); p=0.001], mortality [OR 13.5 (95%CI,6.3‐28.7); p<0.0001] and Poor Outcome [OR 11.2 (95%CI,5.8‐22); p<0.0001] Conclusion Relevant SARS‐CoV‐2 viremia in the first week of hospitalisation was associated with higher in‐hospital mortality, ICU admission, and Poor Outcome. Findings observed in the prospective cohort were confirmed in a larger validation cohort. This article is protected by copyright. All rights reserved.

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Presence of SARS-CoV-2 RNA in serum (viremia) of COVID-19 patients has been related to poor prognosis and death. The aim of this study was to evaluate both the ability to detect viremia in COVID-19 patients of two commercial reverse real-time-PCR (rRT-PCR) tests, Cobas® and TaqPath™, comparing them with a gold standard method, and their implementation in microbiology laboratories. This retrospective cohort study included 303 adult patients (203 diagnosed with COVID-19 and 100 non-COVID-19 patients) admitted to a tertiary hospital, with at least one serum sample collected within the first 48 hours from admission. A total of 365 serum samples were included: 100 from non-COVID-19 patients (pre-pandemic and pandemic control groups) and 265 from COVID-19 patients. Serum samples were considered positive when at least one target was detected. All patients in control groups showed negative viremia. Cobas® and TaqPath™ tests showed specificity and Positive Predictive Value over 96%. Nevertheless, sensitivity (53.72 and 73.63, respectively) and Negative Predictive Value (64.78 and 75) were lower. Viremia difference between ICU and non-ICU patients was significant (p ≤ 0.001) for both techniques. Consequently, SARS-CoV-2 viremia detection by both rRT-PCR tests should be considered a good tool to stratify COVID-19 patients and could be implemented in microbiology laboratories.