Speedy antigen assessments present decrease sensitivity for Omicron than for earlier SARS-CoV-2 variants

In a current research revealed on the medRxiv* preprint server, researchers carried out an analytical susceptibility check with cultured extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant in seven antigen-detecting fast diagnostic (Ag-RDTs).

Study: Analytical sensitivity of seven SARS-CoV-2 antigen-detecting rapid tests for Omicron variant. Image Credit: Roman Zaeits / Shutterstock.com

Examine: Analytical sensitivity of seven SARS-CoV-2 antigen-detecting fast assessments for Omicron variant. Picture Credit score: Roman Zaeits / Shutterstock.com

Background

The emergence of a brand new SARS-CoV-2 VOC necessitates a research of its potential affect on diagnostic efficiency. The SARS-CoV-2 Ag-RDT is advantageous for its capability to supply fast outcomes, low price, and stay unbiased of the laboratory on the level of care. Whereas the sensitivity of the Ag-RDT is much less when in comparison with the gold normal reverse-transcriptase polymerase chain response (RT-PCR) assay, this technique permits dependable detection of excessive viral masses related to the presence of infectious viruses.

The SARS-CoV-2 Omicron variant was reported for the primary time in November 2021 in South Africa and is characterised by numerous mutations as in comparison with different circulating variants. Aside from the huge variety of spike mutations, the Omicron variant additionally has mutations within the nucleocapsid protein, which is the goal of just about all Ag-RDTs.

Two mutations present in Omicron, together with the R203K and G204R have already been described in some sequences of SARS-CoV-2 and have been associated to elevated sub-genomic ribonucleic acid (RNA) and elevated viral masses. Moreover, the Del31-33 deletion is discovered within the Omicron nucleocapsid protein, together with one other P13L mutation, which is current in some however not all Omicron sequences. Data on the potential affect of those mutations on the efficiency of Ag-RDTs will not be but obtainable.

In regards to the research

Within the present research, the analytical sensitivity of the aesthetic virus to the Omicron variant and in contrast it to information beforehand obtained on different SARS-CoV-2 variants of concern (VOCs) together with the Alpha, Beta, Gamma, and Delta variants, in addition to a pre-VOC isolate of SARS-CoV-2 utilizing seven Ag-RDTs.

All viruses had been remoted from medical samples and had been cultivated in Vero-E6 cells. The Omicron variant, initially remoted on the Vero-TMPRSS cells, was then crossed by a inventory passage (p2) ready on VeroE6. The unique sufferers’ sequence, in addition to the virus isolate of the passage, had the next mutations and deletion within the nucleocapsid: R203K, G204R, P13L, and Del31-33.

The researchers adopted the producers’ directions to carry out all Ag-RDT assays, excluding the addition of a 5 microliter (μL) virus dilution into the proprietary buffer, after which utilized to the Ag-RDT in duplicates below Organic Security Laboratory 3 (BSL3) situations. Ag-RDT buffer with no virus was used as a adverse management. The seen check band within the presence of a visual management band was thought of optimistic.

Warmth map primarily based on Log10 PFU/mL for analytical sensitivity of seven Ag-RDTs assays with an early-pandemic SARS-CoV-2 isolate (B.1.610), the VOCs Alpha, Beta, Gamma and Delta compared Omicron. Ag-RDTs used: I) Panbio COVID-19 Ag Speedy check gadget (Abbott); II) Normal Q COVID-19 Ag (SD Biosensor/Roche); III) Positive Standing (Premier Medical Company); IV) 2019-nCoV Antigen check (Wondfo); V) Beijng Tigsun Diagnostics Co. Ltd (Tigsun); VI) Onsite COVID-19 Ag Speedy Take a look at (CTK Biotech); VII) Flowflex (ACON Biotech). Analytical sensitivity for early-pandemic SARS-CoV-2 B.1.610, Alpha, Beta, Gamma and Delta have already been revealed earlier than however had been added right here for consistency causes and higher interpretability of the info on Omicron.

Examine findings

The analytical sensitivity to detect the SARS-CoV-2 Omicron variant was decrease than that for the opposite VOCs in many of the assessments evaluated. The best general sensitivity for all SARS-CoV-2 used was proven by Flowflex, which detected Omicron with barely increased sensitivity than Delta variant however decrease than Alpha, Beta, Gamma, and pre-VOC SARS-CoV-2 strains.

On this analytical technique utilizing a cultured virus, appreciable heterogeneity in sensitivity patterns throughout variants and between particular person assays was additionally noticed. The mutations within the nucleocapsid protein probably affected the totally different epitopes utilized in every check, which could clarify the variations in analytical sensitivity between Ag-RDTs.

Conclusions

Whereas analytical assessments with a cultured virus could also be an alternative choice to medical sensitivity, they don’t seem to be an alternative choice to medical evaluations and have numerous limitations. The connection between infectious viruses, viral proteins, and RNA could differ between affected person specimens and virus isolates in tradition.

Different components reminiscent of in vivo excretion of infectious viruses and general viral load might additional affect the efficiency of medical trials. Because of this, extra research on the diagnostic accuracy of Ag-RDTs for the brand new Omicron VOC are urgently required to tell public well being responses.

*Essential discover

medRxiv publishes preliminary scientific studies that aren’t peer-reviewed and, due to this fact, shouldn’t be thought to be conclusive, information medical observe/health-related habits, or handled as established info.

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