BMJ Open (Jun 2021)

Evaluation of the IgG antibody response to SARS CoV-2 infection and performance of a lateral flow immunoassay: cross-sectional and longitudinal analysis over 11 months

  • David Hunter,
  • Peter Sharpe,
  • Louise J Robertson,
  • Julie S Moore,
  • Kevin Blighe,
  • Kok Yew Ng,
  • Nigel Quinn,
  • Fergal Jennings,
  • Gary Warnock,
  • Mark Clarke,
  • Kathryn Maguire,
  • Sharon Rainey,
  • Ruth K Price,
  • William P Burns,
  • Amanda M Kowalczyk,
  • Agnes Awuah,
  • Sara E McNamee,
  • Gayle E Wallace,
  • Steve Sager,
  • Connie Chao Shern,
  • M Andrew Nesbit,
  • James A D McLaughlin,
  • Tara Moore

DOI
https://doi.org/10.1136/bmjopen-2020-048142
Journal volume & issue
Vol. 11, no. 6

Abstract

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Objective To evaluate the dynamics and longevity of the humoral immune response to SARS-CoV-2 infection and assess the performance of professional use of the UK-RTC AbC-19 Rapid Test lateral flow immunoassay (LFIA) for the target condition of SARS-CoV-2 spike protein IgG antibodies.Design Nationwide serological study.Setting Northern Ireland, UK, May 2020–February 2021.Participants Plasma samples were collected from a diverse cohort of individuals from the general public (n=279), Northern Ireland healthcare workers (n=195), pre-pandemic blood donations and research studies (n=223) and through a convalescent plasma programme (n=183). Plasma donors (n=101) were followed with sequential samples over 11 months post-symptom onset.Main outcome measures SARS-CoV-2 antibody levels in plasma samples using Roche Elecsys Anti-SARS-CoV-2 IgG/IgA/IgM, Abbott SARS-CoV-2 IgG and EuroImmun IgG SARS-CoV-2 ELISA immunoassays over time. UK-RTC AbC-19 LFIA sensitivity and specificity, estimated using a three-reference standard system to establish a characterised panel of 330 positive and 488 negative SARS-CoV-2 IgG samples.Results We detected persistence of SARS-CoV-2 IgG antibodies for up to 10 months post-infection, across a minimum of two laboratory immunoassays. On the known positive cohort, the UK-RTC AbC-19 LFIA showed a sensitivity of 97.58% (95.28% to 98.95%) and on known negatives, showed specificity of 99.59% (98.53 % to 99.95%).Conclusions Through comprehensive analysis of a cohort of pre-pandemic and pandemic individuals, we show detectable levels of IgG antibodies, lasting over 46 weeks when assessed by EuroImmun ELISA, providing insight to antibody levels at later time points post-infection. We show good laboratory validation performance metrics for the AbC-19 rapid test for SARS-CoV-2 spike protein IgG antibody detection in a laboratory-based setting.