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Practice Practice Pointer

Testing for SARS-CoV-2 antibodies

BMJ 2020; 370 doi: https://doi.org/10.1136/bmj.m3325 (Published 08 September 2020) Cite this as: BMJ 2020;370:m3325

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  1. Jessica Watson, general practitioner and National Institute for Health Research doctoral research fellow1,
  2. Alex Richter, senior lecturer and consultant in clinical immunology2,
  3. Jonathan Deeks, professor of biostatistics3 4
  1. 1Centre for Academic Primary Care, Bristol Medical School, University of Bristol, Bristol, UK
  2. 2Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK
  3. 3Test Evaluation Research Group, Institute of Applied Health Research, University of Birmingham, Birmingham, UK
  4. 4NIHR Birmingham Biomedical Research Centre at the University Hospitals Birmingham NHS Foundation Trust and the University of Birmingham, UK
  1. Correspondence to J Watson Jessica.Watson{at}bristol.ac.uk

What you need to know

  • Positive antibodies show evidence of previous exposure to SARS-CoV-2 virus

  • Antibody testing should be undertaken at least two weeks after onset of symptoms

  • The sensitivity and specificity of antibody tests vary over time and results should be interpreted in the context of clinical history

  • Antibody testing might have a useful role in diagnosing covid-19 in patients with late presentation, prolonged symptoms, or negative results from reverse transcription polymerase chain reaction tests

  • Evidence is currently insufficient to know whether individuals with SARS-CoV-2 antibodies have protective immunity

As the covid-19 pandemic has unfolded, interest has grown in antibody testing as a way to measure how far the infection has spread and to identify individuals who may be immune.1 Testing also has a clinical role, given the varying symptoms of covid-19 and false negative results of reverse transcription polymerase chain reaction (RT-PCR) tests, particularly when swabs are taken more than five days after symptom onset and sensitivity of RT-PCR tests starts to decrease.23 In May, the UK government announced that antibody testing should be offered to anyone having their blood taken who wants to know whether they have been infected with SARS-CoV-2, even if there is “not a specific clinical indication,”4 yet currently there is no clear guidance for clinicians on how to interpret these results or how they fit into clinical pathways. In this article we offer an approach to antibody testing in individuals with and without symptoms suggestive of current or past SARS-CoV-2 infection.

How might antibody testing be used?

Covid-19 antibody testing has been the focus of much research and press coverage. Four possible reasons are proposed for SARS-CoV-2 antibody testing:

  1. For diagnosis of individuals with current symptoms suggestive of covid-19, when antigen testing has failed to detect SARS-CoV-2, especially in those who present two weeks or more after symptom onset (when …

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