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Interpreting test results. Positive result. A positive COVID-19 IgG antibody test means that you have previously had or have been exposed to the virus that causes COVID-19, and that your immune system developed antibodies in response to it.
- Context
- Antibody Response Against Sars-Cov-2
- Antibody Testing Capability and Uses
- Immunity Against Sars-Cov-2 – Current Understanding
- Result Interpretation and Sars-Cov-2 Antibody Mechanics
- Assay Types
- Evidence Base
- Probabilistic Language
People are increasingly accessing antibody testing, either through various different surveillance studies, private providers, or directly through government-supported services. As more people access antibody tests there is an increasing chance that people approach health care professionals for advice, particularly after vaccination. This guidance p...
Most people infected with SARS-CoV-2 generate antibodies against the structural proteins of the virus. Most antibodies are made against parts of the spike (S) and nucleocapsid (N) proteins. Tests available to NHS clinicians are lab-based and measure antibodies made against these proteins: anti-S or anti-N antibodies. All SARS-CoV-2 vaccines current...
Testing for anti-SARS-CoV-2 antibodies has several uses: 1. to inform if a patient is likely to benefit from monoclonal antibody (laboratory-made antibodies that attack the virus) treatments in hospital 2. to understand vaccine effectiveness, monitor the impact of variants of concern (VOCs) and estimate prevalence of infection
Previous infection or immunisation are highly likely to provide effective protection from death and severe disease in those who are subsequently infected. This protection is highly likely to be similar across age groups. It is almost certain that variants will continue to emerge and that the protective effect of prior exposure or vaccination will b...
The levels of antibody (antibody titre) produced after vaccination or infection vary. In general, more severe disease tends to lead to higher antibody titres once the patient has recovered from their first infection. Anti-S antibodies are present in the vast majority (greater than 99%) of individuals[footnote 1]28 days after a full SARS-CoV-2 vacci...
Lab-based assays
Lab-based assays are considered ‘gold-standard’. UK Health Security Agency (UKHSA), NHS labs and certain private providers offer lab-based assays of blood samples against the anti-S or anti-N response. UKHSA regularly reviews the performance of antibody assays and you can find more information on these reviews on GOV.UK.
Point of care assays
Point of care (POC) assays are, generally, less sensitive than lab-based assays. Clinical specificity varies between assays. These tests are routinely used in surveillance studies where results can be adjusted relative to performance of the assay of choice. POCassays are not recommended for individual use but are a useful tool for surveillance and research studies.
Longitudinal surveys of reinfections with SARS-CoV-2 and the antibody response over time are extensive in the UK. These include general population studies such as the ONSCOVID-19 Infection Survey and priority cohort surveillances such as healthcare workers (SIREN) and care home staff and residents (Vivaldi). These studies have contributed to an eme...
~0% to 8%: remote chance~10% to 20%: highly unlikely~25% to 35%: unlikely~40% to 50%: realistic possibilityJul 12, 2022 · The spike antibody test detects antibodies that are produced by the immune system in response to COVID-19 infection AND antibodies that develop after receiving the COVID-19 vaccination. If you have a positive test result, you have been recently infected with COVID-19, OR you have made antibodies as a response to a recent COVID-19 vaccination.
Results provided measure antibody levels to proteins produced by the original strain of the SARS-CoV-2 virus (SARS-CoV-2 Spike IgG and SARS-CoV-2 Spike ACE2), and by the Omicron strain of the SARS-CoV-2 virus specifically (SARS-CoV-2 Omicron Spike ACE2).
Antibodies against SARS-CoV-2, which is the virus that causes COVID-19, can be measured in your blood. These COVID-19 antibody levels are at their highest (peak) about 28 days after vaccination or after infection with COVID-19 and then slowly fall.
The SARS-CoV-2 Spike IgG test checks the level of COVID-19 antibodies in your blood. What do these results mean? What levels are “normal”? The SARS-CoV-2 Spike ACE2 test estimates how much of the original COVID-19 strain would be blocked by your antibodies.
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Aug 22, 2021 · Information for healthcare workers on the types of coronavirus (COVID-19) antibody tests available and how to interpret results. From: UK Health Security Agency
