ABSTRACT
Introduction: As vaccination against SARS-CoV-2 progresses rapidly around the world, reliable detection of SARS-CoV-2 specific neutralizing antibodies (NAb) has become an indispensable component of serological diagnostics. We evaluated the performance of four commercially available tests, i.e. two lateral flow assays (Coris BioConcept COVID-19 Sero NP/RBD and Concile InfectCheck COVID-19 NAb) and two surrogate ELISA (sELISA) tests (EUROIMMUN SARS-CoV-2 NeutraLISA and AdipoGen SARS-CoV-2 Neutralizing Antibodies Detection Kit) in comparison with an in-house SARS-CoV-2 micro neutralization test as reference. Methods: A total of 334 sera were tested, including 30 samples collected prior to the emergence of SARS-CoV-2, 128 sera from convalescent patients as well as 176 sera from partially or fully vaccinated individuals.Results: The overall sensitivity of LFAs differed and was 71.6% for the Coris and 98.4% for the Concile. In contrast, overall sensitivity of the NeutraLISA was 86% and 98% for the AdipoGen. All test showed the highest sensitivity when testing samples from fully vaccinated individuals with both sELISA achieving 100% sensitivity. Overall specificity was 89.3% for the Coris and only 58.3% for the Concile. Similarly significant differences were observed for both sELISA, with an overall specificity of 82.1% for the NeutraLISA and only 54.8% for the AdipoGen. All tests showed a 100% specificity when testing negative control samples while specificities were lowest when testing samples from only partially vaccinated individuals. Conclusion: Our findings support the potential use of the Concile LFA and both sELISA for the detection of NAbs against SARS-CoV-2, especially to determine NAb levels after complete vaccination.
Subject(s)
COVID-19ABSTRACT
A number of RT-qPCR assays for the detection of SARS-CoV-2 have been published and are listed by the WHO as recommended assays. Furthermore, numerous commercial assays with undisclosed primer and probe sequences are on the market. As the SARS-CoV-2 pandemic progresses, the virus accrues mutations, which in some cases - as seen with the B.1.1.7 variant - can outperform and push back other strains of SARS-CoV-2. If mutations occur in primer or probe binding sites, this can impact RT-qPCR results and impede SARS-CoV-2 diagnostics. Here we tested the effect of primer mismatches on RT-qPCR performance in vitro using synthetic mismatch in vitro transcripts. The effects of the mismatches ranged from a shift in ct values from -0.13 to +7.61. Crucially, we found that a mismatch in the forward primer has a more detrimental effect for PCR performance than a mismatch in the reverse primer. Furthermore, we compared the performance of the original Charite RdRP primer set, which has several ambiguities, with a primer version without ambiguities and found that without ambiguities the ct values are ca. 3 ct lower. Finally, we investigated the shift in ct values observed with the Seegene Allplex kit with the B.1.1.7 SARS-CoV-2 variant and found a three-nucleotide mismatch in the forward primer of the N target.
ABSTRACT
Background The detection of SARS-CoV-2 with rapid diagnostic tests has become an important tool to identify infected people and break infection chains. These rapid diagnostic tests are usually based on antigen detection in a lateral flow approach. Aims & Methods While for PCR diagnostics the validation of a PCR assay is well established, for antigen tests e.g. rapid diagnostic tests there is no common validation strategy. Here we present the establishment of a panel of 50 pooled clinical specimens that cover a SARS-CoV-2 concentration range from approximately 1.1 × 10 9 to 420 genome copies per mL of specimen. The panel was used to evaluate 31 rapid diagnostic tests in up to 6 laboratories. Results Our results show that there is significant variation in the detection limits and the clinical sensitivity of different rapid diagnostic tests. We conclude that the best rapid diagnostic tests can be applied to reliably identify infectious individuals who are presenting with SARS-CoV-2 loads correlated to 10 6 genome copies per mL of specimen. Infected individuals displaying SARS-CoV-2 genome loads corresponding to less than 10 6 genome copies per mL will be identified by only some rapid diagnostics tests, while many tests miss these viral loads to a large extent. Conclusions Sensitive RDTs can be applied to identify infectious individuals with high viral loads, but not to identify infected individuals.
ABSTRACT
Abstract Objective Independent evaluation of the sensitivity of CE-marked SARS-CoV-2 antigen rapid diagnostic tests (Ag RDT) offered in Germany. Method The sensitivity of 122 Ag RDT was adressed using a common evaluation panel. Minimum sensitivity of 75% for panel members with CT<25 was used for differentiation of devices eligible for reimbursement in in the German healthcare system. Results The sensitivity of different SARS-CoV-2 Ag RDT varied over a wide range. The sensitivity limit of 75% for panel members with CT <25 was met by 96 of the 122 tests evaluated; 26 tests exhibited lower sensitivity, few of which were completely failing. Some devices exhibited high sensitivity, e.g. 100% for CT<30. Conclusion This comparative evaluation succeeded to distinguish less sensitive from better performing Ag RDT. Most of the Ag RDT evaluated appear to be suitable for fast identification of acute infections associated with high viral loads. Market access of SARS-CoV-2 Ag RDT should be based on minimal requirements for sensitivity and specificity.
Subject(s)
Acute DiseaseABSTRACT
In the current pandemic of SARS-CoV-2, rapid identification of infected individuals is crucial for management and control of the outbreak. However, transport of samples, sample processing and RT-qPCR analysis in laboratories are time-consuming. Here we present a nucleic acid-based test format - pulse controlled amplification - that allows detection of SARS-CoV-2 directly from up to eight swab samples simultaneously without the need for RNA extraction within 20 min in a point-of-care setting.
ABSTRACT
Background: In coronavirus disease 2019 (COVID-19), current case definitions presume mainly lower respiratory tract infection. However, cases seen outside the epicenter of the epidemic may differ in their overall clinical appearance due to more sensitive case finding. Methods: We studied viral load courses by RT-PCR in oro- and nasopharyngeal swabs, sputum, stool, blood, and urine in nine hospitalized cases. Infectious virus was detected by cell culture. Active replication was demonstrated by analysis of viral subgenomic replicative intermediates. Serology including neutralization testing was done to characterize immune response. Results: Seven cases had upper respiratory tract disease. Lower respiratory tract symptoms seen in two cases were limited. Clinical sensitivity of RT-PCR on swabs taken on days 1-5 of symptoms was 100%, with no differences comparing swab and sputum samples taken simultaneously. Average viral load was 6.76x10E5 copies per swab during the first 5 days. Live virus isolates were obtained from swabs during the first week of illness. Proof of active viral replication in upper respiratory tract tissues was obtained by detection of subgenomic viral RNA. Shedding of viral RNA from sputum outlasted the end of symptoms. Seroconversion occurred after about one week. Conclusions: The present study shows that COVID-19 can often present as a common cold-like illness. SARS-CoV-2 can actively replicate in the upper respiratory tract, and is shed for a prolonged time after symptoms end, including in stool. These findings suggest adjustments of current case definitions and re-evaluation of the prospects of outbreak containment.