Study design
We report data from an investigator-initiated, single-center, prospective registry study to evaluate Vivalytic™SARS-CoV-2 Multiplex POC (Bosch Healthcare Solutions GmbH; Stuttgarter, Germany) COVID-19 test in clinical practice and to evaluate CT value at admission for risk stratification in hospitalized patients conducted at the Severinenklösterchen Hospital—University of Cologne.
The protocol of this study conforms to the ethical guidelines of the 1975 Declaration of Helsinki and was approved by the institutional ethical committee of the Ärztekammer Nordrhein (20211001).
Study population
All-comers admitted to the hospital over 18 years were eligible for inclusion. Hospital rules dictated that every patient admitted had to be tested. Tested patients were picked randomly for participation.
The decision to perform a PCR-test for SARS-CoV-2 was made independently of study inclusion by the treating physician and patients were asked to participate before the test results were available.
Written informed consent was obtained from all patients prior to study inclusion.
Patients with a positive PCR-test for SARS-CoV-2 were allocated to the “positive” group, patients with a negative PCR-test for SARS-CoV-2 to the control group (Fig. 1). Every patient was then tested two additional times using Vivalytic SARS-CoV-2 Test, and SARS-CoV-2 Rapid Antigen Test respectively. All nasopharyngeal swabs were taken by nurses or trained personnel.
Study plan
Patients admitted to the hospital between January and May 2021 were randomly asked to participate in the study. If patients agreed to participate, overall characteristics such as sex, age and medical history were recorded.
To characterize the severity of the course of disease in COVID-19, patients were divided according to the length of stay (LOS): A prolonged LOS was defined as equal to or greater than the median length of hospital stay. All clinical data gathered during this period was obtained from the electronic patient file. During follow-up no interventions were applied for the purpose of this study and all therapeutic and diagnostic procedures were applied as part of standard care at the discretion of the treating physicians. Finally, participants were contacted by phone and asked about the course of disease using a standardized questionnaire after 3 months. Herein, the patients were asked to rank their current physical fitness on a scale from 0 to 100% as they felt it affected by their COVID-19 disease.
Measurements
SARS-CoV-2 testing using Allplex™ 2019-nCOV Assay (Seegene, Seoul, Korea: polymerase chain reaction assay (PCR) targeting envelope protein- (E-), RNA-dependent RNA polymerase- (RdRP-), and N- genes) was performed by an external laboratory with Applied Biosystems™ 7500 Real-Time PCR System according to the manufacturer’s guidelines.
For analysis with Bosch Vivalytic SARS-CoV-2 assay (Bosch Healthcare Solutions GmbH, Waiblingen, Germany) using the Vivalytic SARS-CoV-2 analyzer, samples were collected in a guanidine thiocyanate-based medium (eNAT® [COPAN Diagnostics Inc.; Murrieta, USA]), stabilizing the viral RNA and completely inactivating the microbial viability. Vivalytic SARS-CoV-2 analyzer is a portable device and works fully automatically.
Roche SARS-CoV-2 Rapid Antigen Test is an immunochromatographic assay for qualitative detection of SARS-CoV-2 infection in nasopharyngeal swabs. The presence of viral antigens in sufficient concentration enables binding to specific mouse monoclonal anti-SARS-CoV-2 antibodies, which is then reflected by the appearance of a visual indicator after the clinical specimen is collected and then deposited in a pre-filled extraction buffer container with the solution being put on the test sample according to manufacturer’s guidelines.
Inter-assay variability was performed conducting repetitive tests on four samples throughout 3 days in triplicates. Intra-assay variability was performed conducting four consecutive assays in duplicates in one run. For intra assay precision we used inactivated whole pathogen sample (AMPLIRUN® TOTAL SARS-CoV-2 RNA Control [Vircell SA, Granada, Spain]) and for inter assay precision we used both, inactivated whole pathogen sample as well as patient samples. 15 000 AMPLIRUN® SARS-CoV-2 RNA CONTROL copies were reconstituted in guanidine thiocyanate-based medium eNAT® (COPAN Diagnostics Inc.; Murrieta, USA) to generate the control sample. Then a dilution series of consecutive samples was performed (1:2; 1:10; 1:100; 1:1000). Both, the results from Bosch Vivalytic (Bosch Healthcare Solutions GmbH; Stuttgarter, Germany) SARS-CoV-2 test for Bosch Vivalytic One as well as the results from the COVID-19 ELISA Elecsys Anti-SARS-CoV-2 assay (Roche Holding AG; Basel, Swiss) were compared to the results from the current gold standard at Severinenklösterchen Hospital – University of Cologne, a centralised laboratory PCR test (Seegene [Seegene, Inc; Seoul, South Korea] AllplexTM2019-nCoV) carried out by an extern laboratory (Laboratory Dr. Wisplinghoff, Horbeller Str. 18–20 Koeln, Germany) to calculate inter- and intra- assay precision.
Statistic
Continuous patient data were compared using a Mann–Whitney U-test or unpaired t-test. Categorical differences between patient groups were compared using Fishers exact test. Continuous variables are presented as mean ± standard deviation (SD) if found to follow a Gaussian distribution according to the D’Agosstino-Pearson omnibus normality test or as median ± lower and upper quartiles if found to follow a non-Gaussian distribution. Categorical patient characteristics are presented as percentages. Spearman nonparametric correlation was used to evaluate the degree to which LOS and CT value at admission move in relation to each other. Independent predictors of LOS above or below median length of stay (Temperature at admission [°C], hemoglobin [g/dl], CT value, thrombocytes [K/μl], sex, age, C-reactive protein [mg/dl], abnormal chest image at admission, Lactate dehydrogenase [U/I], Aspartate Aminotransferase [U/I], Leukocytes [K/μl]) were investigated using multivariate logistic regression.
Descriptive analyses were performed using Graph Pad Prism Version 9.0 (Prism 9 for Mac OS X; GraphPad Software. Inc. La Jolla. CA).