Diagnostics of COVID-19/DARTS (Development and Assessment of Rapid Testing for SARS-CoV-2 Outbreak)

On 12 January 2020, a novel coronavirus was identified as the cause of an outbreak of unexplained pneumonia in Wuhan City, Hubei Province, China. This coronavirus was later named SARS-CoV-2, and the disease it causes COVID-19.

SARS-CoV-2 is a non-segmented, positive sense RNA virus and part of the family of coronaviruses. Similar to the Systemic Acute Respiratory Syndrome (SARS) virus, it binds to the angiotensin-converting enzyme 2 (ACE2) receptor located on type II alveolar cells and intestinal epithelia. SARS-CoV-2 can result in a severe Acute Respiratory Distress Syndrome (ARDS) which is characterised by diffuse alveolar damage and direct viral cytopathic effect on pneumocytes. Some patients who develop COVID19 may respond with a fulminant "cytokine storm" reaction.

As of 23 March 2020, a total of 374,921 COVID-19 cases have been reported in 168 countries with a total of over 16,411 deaths (case fatality amongst confirmed cases of 4.4%) (John Hopkins's Coronavirus Resource centre). Over 293,425 cases and 13,258 deaths have been reported from countries outside mainland China. The World Health Organisation (WHO) declared on the 12th of March the SARS-CoV-2 outbreak a pandemic in the context of a Public Health Emergency of International Concern (PHEIC) [4]. Europe has rapidly become the epicentre of the pandemic and in the UK, cases are increasing daily. There have been 6,724 confirmed cases in the UK as of 23 March 2020, including 190 confirmed inpatients at St George's Hospital NHS Trust (23 March 2020 , Dr. Breathnach, personal communication).

Because of the lack of a validated serological test, the actual number, and therefore the proportion, of people that develop asymptomatic infection remains unknown. This means that an accurate case fatality estimate remains elusive. Due to the rise in the number of diagnostic samples, tests are taking longer than expected. Among the foremost priorities to facilitate public health interventions is a reliable laboratory diagnosis. Prompt case ascertainment is necessary to ensure rapid and effective contact tracing, implementation of infection prevention and control measures according to WHO recommendations, and collection of relevant epidemiological and clinical information.

Because of the lack of a validated serological test, the actual number, and therefore the proportion, of people that develop asymptomatic infections remains unknown. This means that an accurate case fatality estimate remains elusive. Due to the rise of the number of samples to diagnose, tests are taking longer than expected. Among the foremost priorities to facilitate public health interventions is a reliable laboratory diagnosis. Prompt case confirmation is necessary to ensure rapid and effective contact tracing, implementation of infection prevention and control measures according to WHO recommendations, and collection of relevant epidemiological and clinical information.

The experience in China has been that around 15% of patients with confirmed infection develop severe disease and around 5% become critically ill. In the UK, a modelling analysis by the Imperial College COVID-19 Response Team suggests that even with the implementation of self-isolation measures (household quarantine and social distancing) the surge limits for both general wards and ICU beds will be exceeded 8-fold. Furthermore, a relaxation of these mitigation measures is likely to lead to a rebound of cases until there is an effective vaccine - which is not expected for some 12-18 months. We can therefore clearly expect a significant number of inpatients with COVID-19 infection in the UK in the coming months.

The SARS-CoV-2 antigen and antibody lateral flow assay (LFA) development has been led by Mologic, a company based in Bedford. We will use prototype LFA and ELISA that are ready for preliminary evaluation, and subsequently use these tests on-site to evaluate the test at POC. LFA have been developed for SARS-CoV-2 antigen detection in throat/ nose swabs and detection of IgG and IgM in blood/serum and SARS-CoV-2 antigen detection, IgG, IgM and IgA in saliva. Saliva is an exciting sample to use as it is far easier to use than blood or throat / nose swabs for potential self-testing.

Additionally, it is currently unknown why some patients develop severe COVID-19, while others affected by the same SARS-CoV-2 infection display only mild symptoms. Co-morbidities such as hypertension, kidney disease and diabetes have been linked to poorer prognosis and clinical outcomes. However, a proportion of patients of younger age and without comorbidities also develop severe disease- and there is a need for greater understanding of the immunopathogenesis of severe COVID-19 infection is important.

The use of diagnostics developed within this study will improve the management of cases of COVID-19. The LFA are rapid, easy to use and designed to be affordable globally. The rapid diagnosis of SARS-CoV-2 with antigen detection will allow patients to be rapidly triaged in hospital, GP surgeries and other places such as immigration areas. They are sufficiently cheap to be appropriate for use in low- and middle-income countries. The use of antibody detection will allow both for diagnosis of immunological response to acute infections as well as after patients have recovered later . To utilise these tests appropriately an understanding of dynamic immunopathological changes over time is necessary.

Characterisation of immune response and susceptibility and its association with viral clearance and disease progression on in large cohorts with varied disease severity is important to assist clinical risk prediction outcomes and evaluate the potential for novel immunotherapeutic interventions. Immune response characteristics may have predictive and prognostic value, with early adaptive immune responses possibly correlated with improved clinical outcomes.