SARS-CoV-2 lateral flow antigen tests: evaluation of VOC1 (Kent, UK) and VOC2 (South Africa)
Published 12 February 2021
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1. Working with academic collaborators at the University of Oxford, Public Health England (PHE) Porton Down has been evaluating the performance of lateral flow devices (LFDs) since mid-August 2020. Over 80 have been considered to date, approximately 30% of which have progressed to extended evaluation on clinical samples at Phase 3.
2. In December 2020, the leading LFDs were tested against a large batch of clinical VTM swab samples from the Lighthouse Laboratory at Milton Keynes. These samples contained a significant number representative of the new variant strain VOC-202012/01 (VOC1 Kent, UK, B.1.1.7) and all were detected where the viral titre was above LOD for the LFD, as previously reported on GOV.UK on 23 December 2020.
3. Subsequently, these LFDs and the Orient Gene LFD have also been successfully evaluated using characterised cultured virus VOC-202012/01 (VOC1 Kent, UK) from material provided by colleagues at PHE Colindale, and also cultured virus for the VOC-202012/02 (VOC2 South Africa, B.1.351 variant). Stocks of cultured virus were diluted down in synthetic mucus and replicates tested at each dilution following manufacturers instructions. The LFDs, including those currently in use, successfully detected samples containing the new variants.
| Variant of concern, virus titre and detection level | ||||
|---|---|---|---|---|
| VOC1 | Kent, UK | VOC2 | South Africa | |
| Lateral Flow Device | 104 pfu/ml | 103 pfu/ml | 104 pfu/ml | 103 pfu/ml |
| Fortress | Detected | Detected | Detected | Detected |
| Roche SD Biosensor swab | Detected | Detected | Detected | Detected |
| Abbott Panbio | Detected | Detected | Detected | Detected |
| Innova | Detected | Detected | Detected | Detected |
| Surescreen | Detected | Detected | Detected | Detected |
| Orient Gene | Detected | Detected | Detected | Detected |
4. The VOC1 (Kent, UK) and VOC2 (South Africa) both contain multiple nucleotide changes across the genome which result in amino acid substitutions and other changes in different proteins. These include a large number of changes in the spike protein and a lesser number in the nucleocapsid protein. Whilst some lateral flow tests in development are using the spike protein, the majority of those tested use the nucleocapsid protein as the antigen target; these include the current lateral flow tests in use. The changes in both variants for these antigen targets are listed in the table below.
| Variant | VOC 1 (Kent, UK) | VOC2 (South Africa) |
|---|---|---|
| Spike protein | N501Y; A570D; D614G; P681H; T716I; S982A; D1118H; 69/70 HV deletion; 144Y deletion | D80A, D215G, K417N, E484K, N501Y, D614G, A701V |
| Nucleocapsid protein | D3L; R203K; G204R; S235F | T205I |
5. In summary, the LFDs listed above, all of which target the nucleocapsid protein, have detected the new variants that contain a limited number of amino acid changes from the original viral sequence in the target antigen. This does not affect their performance and we will monitor further variant changes as they arise as part of our ongoing evaluation programme.