Clinical usefulness of fully automated chemiluminescent immunoassay for quantitative antibody measurements in COVID-19 patients.

Since December 2019, we have been in the battlefield with a new threat to the humanity, known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), characterized by viral pneumonia. It may be asymptomatic or cause various symptoms, ranging from flu-like symptoms to acute respiratory distress syndrome and eventually death. At present, the only reliable test for COVID-19 diagnosis is quantitative reverse transcriptase-polymerase chain reaction. Assessing the immune response against SARS-CoV-2 could increase the detection sensitivity of infected population. Hereby, we report the performances of a fully automated chemiluminescent immunoassay (CLIA) on 276 serum samples. One hundred samples obtained from COVID-19 negative subjects (COVID-19 free) were analyzed to evaluate the diagnostic specificity of antibody (Ab) detection. Thereafter, 176 samples obtained from 125 patients with confirmed COVID-19 (COVID-19 patients) were selected to assess the diagnostic sensitivity of the CLIA. All samples were analyzed on MAGLUMI 800 platform. All COVID-19 free samples had Ab levels below the cutoff values. Hence, the diagnostic specificity was estimated at 100% (95% confidence interval [CI] = 96.3-100.0; positive predictive value = 100%). By the 18th day from the onset of symptoms, we reached an optimal diagnostic sensitivity (more than 95.0%) In fact, the diagnostic sensitivity increased over time and between 15 and 25 days after symptoms onset, reached 95.5% (95% CI = 84.9-99.2). The new automated CLIA analyzer appeared to be a robust and reliable method to measure specific Ab against COVID-19 at high throughput. Our data suggest that combining Ab and nucleic acid detection could increase diagnostic sensitivity.

Usefulness of a multiplex immunodot in case of discordant results between automated COVID-19 serological assays.

BACKGROUND: At present, the only reliable test for COVID-19 diagnosis is RT-qPCR. Serological assays have been widely used to increase the detection sensitivity of infected population. Hereby, we report the performance of a new pan-IgG multiplex Enzyme Immunoassay (immunodot) method for exploration of discrepant SARS-COV-2 serological results. METHODS: A retrospective study on 38 residual serum samples from recovered COVID-19 subjects with discordant serological results on Roche and Snibe platforms, were reanalyzed on a new semi-automated pan-IgG immunodot Enzyme Immunoassay, namely COVIDOT-TEST, in order to find the source of discrepancies and to evaluate the latter method. All samples were analyzed on the BlueDiver® Instrument and all strips were read by the BlueScan® Scanner using Dr DOT® Software. RESULTS: Based on our data, subject samples showed specific IgG reactions on ≥ 2 different antigens on immunodot strips. Of these 38 samples, 97.4 % of samples showed specific IgG reaction against S1 + S2 antigens, 89.5 % showed against RBD antigen, 86.8 % against S2 antigen reaction on the COVIDOT-TEST kit. Specific IgG-S1 antigen and IgG-N antigen reactions were detected in 73.7 % and 65.8 % of the samples, respectively. CONCLUSION: The new semi-automated pan-IgG immunodot Enzyme Immunoassay method appeared to be a reliable assay to confirm suspicious COVID-19 serological screening results.

A biological profile for diagnosis and outcome of COVID-19 patients.

Objectives As severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) pandemic is increasing its victims on a global scale with recurring outbreaks, it remains of outmost importance to rapidly identify people requiring an intensive care unit (ICU) hospitalization. The aim of this study was to identify Coronavirus Disease 2019 (COVID-19) biomarkers, to investigate their correlation with disease severity and to evaluate their usefulness for follow-up. Methods Fifty patients diagnosed with SARS-Cov-2 were included in March 2020. Clinical and biological data were collected at admission, during hospitalization and one month after discharge. Patients were divided into two severity groups: non-ICU (28) and ICU and/or death (22) to stratify the risk. Results Blood parameters in COVID-19 patients at admission showed increased C-reactive protein (CRP) (100%), ferritin (92%), lactate dehydrogenase (LDH) (80%), white blood cell (WBC) count (26%) with lymphopenia (52%) and eosinopenia (98%). There were significant differences in levels of CRP, ferritin, D-dimers, fibrinogen, lymphocyte count, neutrophil count and neutrophil-to-lymphocyte ratio (NLR) among the two severity groups. Mapping of biomarker's kinetics distinguished early and late parameters. CRP, ferritin, LDH, lymphopenia and eosinopenia were present upon admission with a peak at the first week. Late biomarkers such as anemia, neutrophilia and elevated liver biomarkers appeared after one week with a peak at three weeks of hospitalization. Conclusions We confirmed that high-values of CRP, NLR, D-dimers, ferritin as well as lymphopenia and eosinopenia were consistently found and are good markers for risk stratification. Kinetics of these biomarkers correlate well with COVID-19 severity. Close monitoring of early and late biomarkers is crucial in the management of critical patients to avoid preventable deaths.