ABSTRACT
IntroductionMolecular testing for SARS-CoV-2 continues to suffer from delays and shortages. Antigen tests have recently emerged as a viable alternative to detect patients with high viral loads, associated with elevated risk of transmission. While rapid lateral flow tests greatly improved accessibility of SARS-CoV-2 detection in critical areas, their manual nature limits scalability and suitability for large-scale testing schemes. The Elecsys(R) SARS-CoV-2 Antigen assay allows antigen immunoassays to be carried out on fully automated high-throughput serology platforms. MethodsA total of 3139 nasopharyngeal and oropharyngeal swabs were collected at 3 different testing sites in Germany. Swab samples were pre-characterized by RT-qPCR and consecutively subjected to the antigen immunoassay on either the cobas e 411 or cobas e 801 analyzers. ResultsOf the tested respiratory samples, 392 were PCR positive for SARS-CoV-2 RNA. Median concentration was 2.95x104 (interquartile range [IQR] 5.1x102-3.5x106) copies/mL. Overall sensitivity and specificity of the antigen immunoassay were 60.2% (95% confidence interval [CI] 55.2-65.1) and 99.9% (95% CI 99.6-100), respectively. A 93.7% (95% CI 89.7-96.5) sensitivity was achieved at a viral RNA concentration [≥]104 copies/mL ([~]cycle threshold (Ct) value<29.9). ConclusionThe Elecsys SARS-CoV-2 Antigen assay reliably detected patient samples with viral loads of 10,000 copies/mL and higher. It thus represents a viable high-throughput alternative for screening of patients, or in situations where PCR testing is not readily available. Key Summary PointsO_ST_ABSWhy carry out this study?C_ST_ABSO_LIThe SARS-CoV-2 pandemic has led to a surge in demand for reliable, mass diagnostic tests worldwide. C_LIO_LIA thorough clinical evaluation of a fully automated high-throughput Elecsys(R) SARS-CoV-2 Antigen assay on a total of 3139 clinical samples pre-characterized by quantitative RT-PCR was carried out. C_LI What was learned from the study?O_LIThe assay demonstrated excellent specificity (99.9%) and good relative sensitivity, with an overall sensitivity of 60.2% and a sensitivity of 93.7% for samples containing [≥]104 viral RNA copies/mL. C_LIO_LIThe Elecsys SARS-CoV-2 Antigen assay is a viable high-throughput, automated alternative to manual lateral-flow antigen tests. C_LI
ABSTRACT
1BackgroundNew SARS-CoV-2 variants with increased transmissibility, like B.1.1.7 from England or B1.351 from South Africa, have caused considerable concern worldwide. In order to contain the spread of these lineages, it is of utmost importance to have rapid, sensitive and high-throughput detection methods at hand. MethodsAnalytical sensitivity was assessed for both wild-type SARS-CoV-2 and B.1.1.7 lineage by serial dilution. A total of 141 clinical samples were subjected to the test and results compared to a commercial manual typing-PCR assay and NGS. ResultsThe multiplex assay is highly sensitive for detection of SARS-CoV-2 RNA in clinical samples, with an LoD of 25.82 cp/ml (CI: 11.61 - 57.48). LoDs are slightly higher for the HV68/70 deletion (111.36 cp/ml; CI: 78.16 - 158.67) and the N501Y SNP (2548.04 cp/ml, CI: 1592.58 - 4076.73). A total of 141 clinical samples were tested with the assay, including 16 samples containing SARS-CoV-2 of the B.1.1.7 lineage. Three non-B.1.1.7 samples contained a HV69/70 deletion. All were correctly identified by the multiplex assay. ConclusionWe describe here a highly sensitive, fully automated multiplex PCR assay for the simultaneous detection of del-HV69/70 and N501Y that can distinguish between lineages B.1.1.7 and B1.351. The assay allows for high-throughput screening for relevant variants in clinical samples prior to sequencing.
ABSTRACT
BackgroundSARS-CoV-2 molecular diagnostics is facing material shortages and long turnaround times due to exponential increase of testing demand. ObjectiveWe evaluated the analytic performance and handling of four rapid Antigen Point of Care Tests (AgPOCTs) I-IV (Distributors: (I) Roche, (II) Abbott, (III) MEDsan and (IV) Siemens). Methods100 RT-PCR negative and 84 RT-PCR positive oropharyngeal swabs were prospectively collected and used to determine performance and accuracy of these AgPOCTs. Handling was evaluated by 10 healthcare workers/users through a questionnaire. ResultsThe median duration from symptom onset to sampling was 6 days (IQR 2-12 days). The overall relative sensitivity was 49.4%, 44.6%, 45.8% and 54.9 % for tests I, II, III and IV, respectively. In the high viral load subgroup (containing >106 copies of SARS-CoV-2 /swab, n=26), AgPOCTs reached sensitivities of 92.3% or more (range 92.3%-100%). Specificity was 100% for tests I, II and IV and 97% for test III. Regarding handling, test I obtained the overall highest scores, while test II was considered to have the most convenient components. Of note, users considered all assays, with the exception of test I, to pose a significant risk for contamination by drips or spills. DiscussionBesides some differences in sensitivity and handling, all four AgPOCTs showed acceptable performance in high viral load samples. However, due to the significantly lower sensitivity compared to RT-qPCR, a careful consideration of pro and cons of AgPOCT has to be taken into account before clinical implementation.
