Validation of the Vivalytic SARS-CoV-2 rapid PCR test in lower respiratory tract specimens
The ongoing pandemic of SARS-CoV-2 requires the availability of accurate and rapid diagnostic tests, especially in some clinical settings like emergency and intensive care units (ICU). The objective of this study was to validate the rapid PCR kit Vivalytic SARS-CoV-2 in lower respiratory tract (LRT) specimens.
Material & Methods
A quota 1 :1 :1 sampling of 75 consecutive LRT specimens (broncho-alveolar lavage or aspirate) from hospitalized patients to Intensive Care Units of San Martino Hospital (Genoa, ltaly) between November 2020 and January 2021 was carry out. First, all samples were tested in RT-PCR by using Allplex™ SARS-CoV-2 assay (Seegene lnc., South Korea). Based on RT-PCR results, specimens were categorized into negative, positive with high viral load [cycle threshold (Ct) <30) and positive with low viral load (Ct of 31-35). Later, LRT samples were tested in the rapid PCR assay Vivalytic SARS-CoV-2 (Bosch Healthcare Salutions GmbH, Germany) (Figure 1).
The overall diagnostic accuracy of the Vivalytic SARS-CoV-2 was 97.3% (95% Cl: 90.9-99.3%) with an excellent Cohen’s K of 0.94 (95% Cl: 0.72-1). The sensitivity and specificity were 96% (95% Cl: 86.5-98.9%) and 100% (95% Cl: 86.7-100%), respectively. lndeed, only two false negative results were found and both belonged to patients with low viral loads. Samples with high viral loads had a sensitivity of 100% (Table 1). The distributions of E gene Ct values were similar (Wilcoxon's test: P=0.070) with medians of 35 (IQR: 25-36) and 35 (IQR: 25-35), respectively (Figure 2). At hypothetical positivity rates af 1%, 5%, 10% and 20% the PPV would be 100%, 99.8%, 99.6% and 99.0%, respectively, while NPV would be constantly 100%.
Our results validates Vivalytic SARS-CoV-2 in LRT specimens and found it feasible and highly accurate especially in high viral load samples. This assay is simple, fully automated and rapid with results in about 40min.