REACT-2.1: Evaluation of SARS-CoV-2 lateral flow immunoassays

How accurate are lateral flow immunoassays? This epidemiological study compares LFIAs with other COVID-19 tests


Keywords: SARS-CoV-2; COVID-19; prevalence; PCR; virus; point-of-care diagnostics

Q&A with the REACT team: REACT researchers Dr Atchison and Prof Barclay host a public Q&A session on antibody testing.

Short of a vaccine, testing is the only way out of lockdown.

Prof ara darzi

Description of the Study:

  • Title: REACT-2: a study of SARS-CoV-2 antibody seroprevalence in the community in England.
    – Study 1: Clinical and laboratory evaluation of SARS-CoV-2 lateral flow immunoassays.
  • Principal Investigators: Steven Riley, Christina Atchison, Deborah Ashby, Christl A. Donnelly, Wendy Barclay, Graham Cooke, Helen Ward, Ara Darzi and Paul Elliott.
  • Centers of Implementation: Imperial College London, Imperial College Healthcare NHS Trust and Ipsos MORI.
  • Study Population: Assuming 90% power, a COVID-19 prevalence of 100% (all participants confirmed SARS-CoV-2 positive by RT-PCR), and an expected test sensitivity of 85% we enrol a minimum of 153 participants to evaluate sensitivity with a two-sided delta of 10%.
    The inclusion criteria:
    – Adult ≥ 18 years old.
    – Previous PCR-confirmed SARS-CoV-2 (from nasopharyngeal or throat swab).
    – Date of COVID-19 symptom onset no sooner than 21 days prior to study visit*.
    *≥21 days is chosen to optimise the number of seropositives. Previous studies have shown that ELISA on sera is highly sensitive for IgG from 10 days following symptoms onset. Participants with date of positive PCR test <21 days will be asked to book an appointment (finger prick test and blood sample) for ≥21 days post PCR test.
  • Design: Evaluation of test performance of different LFIAs.
  • Methods: For sensitivity, tests are compared against two standards:
    (i) RT-PCR-confirmed clinical disease (via swab testing).
    (ii) Positivity in patients with either a positive S-ELISA and/or positive DABA score.
    LFIA performance is assessed with:
    (i) Finger-prick self-testing (participant interpretation).
    (ii) Finger-prick self-testing (trained observer interpretation).
    (iii) Serum in the laboratory.

Objectives of the Study:

Principal Objectives: The aim of this epidemiological study is to evaluate the sensitivity and specificity of each COVID-19 lateral flow immunoassays (LFIAs).

More about this Study:

Conclusions: The REACT-2 results and statistics can be found on this page.

Added value: REACT-2 is a series of five sub-studies towards establishing the seroprevalence of antibodies to SARS-CoV-2 in England as an indicator of historical infection. The main study (study 5) uses the same design and sampling approach as REACT-1 using a self-administered lateral flow immunoassay (LFIA) test for IgG antibodies in repeated samples of 100,000 to 200,000 adults aged 18 years and above. To inform study 5, studies 1-4 evaluate performance characteristics of SARS-CoV-2 LFIAs (study 1) and different aspects of feasibility, usability and application of LFIAs for home-based testing in different populations (studies 2-4).

REACT: The REal-time Assessment of Community Transmission (REACT) programme is a series of epidemiological studies that are seeking to improve understanding of how the COVID-19 pandemic is progressing across England. To do this, the programme is carrying out two major pieces of work that are looking at the possibility of using home sampling and testing to track the infection. REACT-1 programme is monitoring coronavirus infection levels over time, while REACT-2 programme is assessing antibody finger-prick tests and using these to estimate how far the virus has spread.

Together REACT-1 and REACT-2 will improve our understanding of the transmission of the virus in the community to help guide policies on continued social distancing and other control measures.

Other studies of REACT: « Clinical and laboratory evaluation of SARS-CoV-2 lateral flow immunoassays« , « Public involvement and pilot testing to assess the feasibility of in-home self-testing for SARS-CoV-2 antibodies« , « Acceptability and usability study of in-home self-testing for SARS-CoV-2 antibodies in a population-based sample » and « Usability and validity of LFIA self-testing in key workers, including the assessment of dry blood spots for SARS-CoV-2 antibody detection and saliva for SARS-CoV-2 viral detection ».

Imperial College London


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