What is the T-Spot® COVID test?
The T-Spot® COVID test can be a complement to the COVID-19 antibody (serology) test to provide a more comprehensive picture of the body’s immune response to SARS-CoV-2. The antibody (serology) test assesses the B-cell response, while the T-Spot® COVID test assesses the T-cell response.
The T-Spot® COVID test is a CE-marked venous blood test based on the standardised ELISPOT (Enzyme Linked ImmunoSpot) technique, that looks for an immune response from T-cells to COVID-19. It determines whether the T cells, or T lymphocytes, are sensitised to SARS-CoV-2, the virus that causes COVID-19. T cell sensitisation can be caused by either previous exposure or vaccination against COVID-19.
There are 3 main parts of our immune system, adaptive, passive and innate. T cells are part of our adaptive immune system and play a big role in immune regulation, viral recognition and, viral destruction and presentation. T cells can either kill the virus themselves (cytotoxic T-cells) or interact with B cells (helper T cells) to enable them to produce antibodies against the virus.
Why is this analysis important?
In short, the T-Spot® COVID test is useful for:
Detection of T cell response to SARS-CoV-2, the virus that causes COVID-19
Identifying individuals that could have had COVID-19, including those who had an asymptomatic infection
Every person’s immune system reacts differently when encountered with a virus or vaccine. A study conducted by Public Health England on healthcare workers using the research version of the T-Spot® COVID test showed that some individuals with COVID-19 can generate T cell responses in the absence of an antibody response and that T-Spot® COVID test results better correlated with previous positive PCR tests than antibody (serology) tests (1).
This is especially true for people with a compromised immune system, such as those undergoing haemodialysis due to end stage kidney disease. In such individuals, the T-Spot® COVID test could more accurately detect previous COVID-19 infection than the antibody (serology) test (2).
T-cell response to viruses such as SARS-CoV-2 may be more durable, robust and outlast antibody responses produced from B-cells.
An analysis of 100 donors showed that the T cell response was still robust at six months following both symptomatic and asymptomatic COVID-19 infections despite decreasing antibody levels (3). Experience from SARS-CoV-1, a closely related coronavirus that caused the SARS epidemic in 2002-2004, showed that T-cell response can last for over 17 years (4).
The results of the T-Spot® COVID test can be “reactive”, “non-reactive” or “borderline”.
A “Reactive” result indicates that the sample contains effector T cells sensitised to SARS-CoV-2. This indicates that it is highly likely that the person has been exposed to the SARS-CoV-2 virus or COVID-19 vaccination.
A “Non-Reactive” result indicates that no effector T cells sensitised to SARS-CoV-2 were detected, and that it is highly unlikely that the person has been exposed to the SARS-CoV-2 virus or COVID-19 vaccination.
A “Borderline” result indicates that it was not possible to reliably determine if the sample contains effector T cells sensitised to SARS-CoV-2 and a retest with a new blood sample is recommended.
Testing should be undertaken at least 14 days after symptom onset or vaccination. If current COVID infection is suspected, you should do a COVID PCR test.
The T-Spot® COVID test does not tell you whether you have conferred immunity against COVID-19. Regardless of the test result, you should always follow government instructions on testing, isolation and vaccination.
1. Wyllie D, Mulchandani R, Jones HE et al. SARS-CoV-2 responsive T cell numbers are associated with protection from COVID-19: A prospective cohort study in key workers. doi: https://doi.org/10.1101/2020.11.02.20222778
2. Clarke CL, Prendecki M, Dhutia A et al. Longevity of SARS-CoV-2 immune responses in hemodialysis patients and protection against reinfection. Kidney Int. 2021 Jun;99(6):1470-1477. https://doi: 10.1016/j.kint.2021.03.009.
3. Zuo J, Dowell A, Pearce H et al. Robust SARS-CoV-2-specific T-cell immunity is maintained at 6 months following primary infection. https://10.1101/2020.11.01.362319