We have introduced COVID-19 (SARS-CoV-2) testing both for active infection, and immunological marker of past infection. The tests are provided by accredited UK partner laboratory. They come as postal kits, and can be self-administered at home therefore there is no need to attend the clinic.
Infection with SARS-CoV-2, an RNA virus, is diagnosed using molecular testing, reverse-transcriptase PCR swab. The incubation period of COVID-19 ranges from between 1 to 14 days, with the majority of cases manifesting with symptoms at 3 – 5 days. The assays used at TDL show a minimum sensitivity of 98% and a specificity of 100%, with no cross-reactivity with other viruses. As with all viral PCR assays, patients with very low viral loads are less likely to be detected. Negative (or ‘NOT detected’) results do not preclude infection with the SARS- CoV-2 virus and should not be the sole basis of a patient treatment/management or public health decision. Where there is a strong clinical suspicion of an early COVID-19 infection repeat sampling should be considered 24-48 hours later. Results should be interpreted by a trained professional in conjunction with the patient’s history and clinical signs and symptoms, and epidemiological risk factors.
Antibody testing can tell whether a person has been previously infected. Most patients who recover from coronavirus have been found to produce antibodies, but it is not yet known if an individual with a positive result showing presence of IgG levels following being infected with SARS-CoV-2 will be protected, either fully or partially from 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 host immune system reacts to the infection by SARS-CoV-2 by producing antibodies from a few days to 2 weeks and beyond. Specific IgG antibodies are produced in the later stages of infection to SARS-CoV-2, and are detectable after RNA is no longer detectable. The persistence of IgG antibodies allows identification of people who have been infected by SARS-CoV-2. It has been recognised that there can be delayed responses in immunocompromised patients.