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1.
Infection ; 2022 May 20.
Article in English | MEDLINE | ID: covidwho-1943482

ABSTRACT

PURPOSE: Omicron is rapidly spreading as a new SARS-CoV-2 variant of concern (VOC). The question whether this new variant has an impact on SARS-CoV-2 rapid antigen test (RAT) performance is of utmost importance. To obtain an initial estimate regarding differences of RATs in detecting omicron and delta, seven commonly used SARS-CoV-2 RATs from different manufacturers were analysed using cell culture supernatants and clinical specimens. METHODS: For this purpose, cell culture-expanded omicron and delta preparations were serially diluted in Dulbecco's modified Eagle's Medium (DMEM) and the Limit of Detection (LoD) for both VOCs was determined. Additionally, clinical specimens stored in viral transport media or saline (n = 51) were investigated to complement in vitro results with cell culture supernatants. Ct values and RNA concentrations were determined via quantitative reverse transcription polymerase chain reaction (RT-qPCR). RESULTS: The in vitro determination of the LoD showed no obvious differences in detection of omicron and delta for the RATs examined. The LoD in this study was at a dilution level of 1:1,000 (corresponding to 3.0-5.6 × 106 RNA copies/mL) for tests I-V and at a dilution level of 1:100 (corresponding to 3.7-4.9 × 107 RNA copies/mL) for tests VI and VII. Based on clinical specimens, no obvious differences were observed between RAT positivity rates when comparing omicron to delta in this study setting. Overall positivity rates varied between manufacturers with 30-81% for omicron and 42-71% for delta. Test VII was only conducted in vitro with cell culture supernatants for feasibility reasons. In the range of Ct < 23, positivity rates were 50-100% for omicron and 67-93% for delta. CONCLUSION: In this study, RATs from various manufacturers were investigated, which displayed no obvious differences in terms of analytical LoD in vitro and RAT positivity rates based on clinical samples comparing the VOCs omicron and delta. However, differences between tests produced by various manufacturers were detected. In terms of clinical samples, a focus of this study was on specimens with high virus concentrations. Further systematic, clinical and laboratory studies utilizing large datasets are urgently needed to confirm reliable performance in terms of sensitivity and specificity for all individual RATs and SARS-CoV-2 variants.

2.
Microorganisms ; 9(9)2021 Sep 16.
Article in English | MEDLINE | ID: covidwho-1410330

ABSTRACT

Rapid antigen tests (RATs) are an integral part of SARS-CoV-2 containment strategies. As emerging variants of concern (VOCs) displace the initially circulating strains, it is crucial that RATs do not fail to detect these new variants. In this study, four RATs for nasal swab testing were investigated using cultured strains of B.1.1 (non-VOC), B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), and B.1.617.2 (Delta). Based on dilution series in cell culture medium and pooled saliva, the limit of detection of these RATs was determined in a laboratory setting. Further investigations on cross-reactivity were conducted using recombinant N-protein from seasonal human coronaviruses (hCoVs). RATs evaluated showed an overall comparable performance with cultured strains of the non-VOC B.1.1 and the VOCs Alpha, Beta, Gamma, and Delta. No cross-reactivity was detected with recombinant N-protein of the hCoV strains HKU1, OC43, NL63, and 229E. A continuous evaluation of SARS-CoV-2 RAT performance is required, especially with regard to evolving mutations. Moreover, cross-reactivity and interference with pathogens and other substances on the test performance of RATs should be consistently investigated to ensure suitability in the context of SARS-CoV-2 containment.

3.
Euro Surveill ; 26(16)2021 04.
Article in English | MEDLINE | ID: covidwho-1200054

ABSTRACT

SARS-CoV-2 variants of concern (VOC) should not escape molecular surveillance. We investigated if SARS-CoV-2 rapid antigen tests (RATs) could detect B.1.1.7 and B.1.351 VOCs in certain laboratory conditions. Infectious cell culture supernatants containing B.1.1.7, B.1.351 or non-VOC SARS-CoV-2 were respectively diluted both in DMEM and saliva. Dilutions were analysed with Roche, Siemens, Abbott, nal von minden and RapiGEN RATs. While further studies with appropriate real-life clinical samples are warranted, all RATs detected B.1.1.7 and B.1.351, generally comparable to non-VOC strain.


Subject(s)
COVID-19 , SARS-CoV-2 , COVID-19 Serological Testing , Germany , Humans
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