Oxford Diagnostic Laboratories offer two types of tests for COVID-19 (SARS-CoV-2). The PCR test for viral RNA, and the serology test for antibodies to SARS-CoV-2.
Why PCR testing?
This is the ‘Do I have COVID-19?’ test. The aim of the PCR test is to understand who has virus present in their upper respiratory tract. It looks for the presence of viral RNA in nasal/throat swabs.
As with all viral PCR assays, patients with very low viral loads are less likely to be detected. Negative results do not mean there is no possibility of infection with the SARS-CoV-2 virus. Where there is a strong clinical suspicion of an early SARS-CoV-2 infection you should consider repeat sampling 24-48 hours later.
Why serology testing?
This is the ‘Have I had COVID-19?’ test. The aim of serology testing is to understand more about who may have come into contact with the virus. The serology test measures for the presence of IgG antibodies to SARS-CoV-2.
Most patients have been found to produce antibodies to SARS-CoV-2 once they have recovered from coronavirus infection. However, whether the presence of IgG following infection can infer protection (either fully or partially) from future infection is yet to be determined.
The ODL service offering
Testing large numbers of people is clearly a challenge. We aim to work with you to make this achievable. Testing involves many stages and our service packages can cover all or some of them to help you achieve what you need more efficiently.
Full service – Complete organisation of large screening events
- Experienced phlebotomists capable of collecting in excess of 100 samples per day (including paediatrics)
- PPE provision
- Supply of all necessary materials including blood collection tubes and needles
- Disposal of all waste (including sharps)
- Complete logistics organisation
- Test completion
- Result delivery
- Coordinator on site during the event
- Support from our Customer Service team, before and after the event
Partial service – Any of the above service elements can be used to best achieve the results you need. We can support you with just phlebotomy services, logistical organisation of screening events, or just with the sample collection and processing, it’s up to you.
We have years of experience organising and carrying out screenings from our work with TB. We are able to carry out screenings in many locations including the workplace, schools, universities and prisons. So we can organise an event according to your needs, no matter what your situation.
Testing data is handled securely and in full compliance with GDPR. All information surrounding any screening event is handled with strict confidentiality, and security of individuals result data is ensured by controlled data distribution and encryption of the results database.
Testing for COVID-19 and TB together
If you are performing a TB screening it may be beneficial to also screen for COVID-19. Depending on the population being screened there may be an advantage to understanding their status relating to SARS-CoV-2 infection.
Protect the testers – by carrying out COVID-19 and TB testing together the potential exposure for the health care worker and the patient is limited – one visit for both tests
Test the vulnerable – there is evidence that having a TB infection can lead to a more severe case of COVID-19. Screening for COVID-19 amongst those suspected of recent exposure to TB makes sense
Test the immunosuppressed – the immunosuppressed are at a higher risk of infection and severity of COVID-19 disease, so you may now choose to screen for both if you were planning to test for only TB.
Choose your test
Coronavirus COVID-19 (SARS-CoV-2) testing by PCR
- Nasal/throat swabs and collection tubes are supplied
- Samples should be taken between days 1-5 from onset of symptoms
- Specimens should be returned at ambient temperature and labelled as containing HIGH RISK specimen
- Send samples on the day they are taken for best results. However, samples are stable at ambient temperature for up to 6 days
Infection with SARS-CoV-2 is diagnosed using reverse-transcription PCR. The assays used show a minimum sensitivity of 98 % and a specificity of 100 %, with no cross-reactivity with other viruses.
The tests being offered are constantly under review as new tests become available. The nature of the current situation means testing for COVID-19 (SARS-CoV-2) is rapidly evolving making this review essential.
Limitations and clinical interpretation
As is the case for all viral PCR tests, patients with very low viral loads are less likely to be detected than those with a higher viral load. Not detected or negative results do not mean that an infection with the SARS-CoV-2 virus is not present and should not be the sole basis of a patient treatment/management or public health decision. If there is strong clinical evidence of SARS-CoV-2 infection, but a negative result is returned repeat sampling should be considered 24-48 hours later.
Results should only be considered in conjunction with the patient’s history, clinical signs and symptoms and epidemiological risk factors as interpreted by a trained professional.
Coronavirus – COVID-19 (SARS-CoV-2) IgG antibody
Testing for the presence of antibodies can tell us whether a person has been previously infected. Most patients who recover from coronavirus have been found to produce antibodies. However, it is not yet known if a positive result for antibodies, showing presence of IgG levels following infection with SARS-CoV-2, will be protective, either fully or partially against future infection, or for how long protective immunity may last.
Testing should be undertaken 14 days or more following exposure or onset of symptoms.
The persistence of IgG antibodies allows identification of people who have been infected by SARS-CoV-2. Test development relating to SARS-CoV-2 is rapidly evolving. Laboratory review of new assays as they become available is essential.
False negatives can occur due to a low level of antibodies, clearance of virus without an antibody response or because of recent infection without allowing time for the IgG antibody response to build to detectable levels. Positivity for antibodies does not mean an individual is immune to subsequent re-infection by SARS-CoV-2, as it is still unclear if the antibodies being detected are neutralising/functional antibodies, nor does it give an indication of how long those antibodies may remain in the individual.
Interpretation of results
COV-2 IgG < 1.4 Not Detected (Negative)
COV-2 IgG >= 1.4 Detected (Positive)
Specificity 100 %
Sensitivity 97.5 %
Results should be used in conjunction with information available from clinical evaluation and other diagnostic procedures. It has been recognised that there can be delayed responses in immunocompromised patients.
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For more information on COVID-19, please click here
For COVID-19 Testing FAQs, please click here
The COVID-19 tests may be performed by a 3rd party laboratory. Any 3rd party laboratory used is UKAS accredited and situated in the UK. UKAS accreditation specifically for the COVID-19 testing has been applied for as an extension of scope and is awaiting UKAS accreditation.