Virus World

The rapid tests for hospitals and care homes will distinguish between Covid-19 and seasonal illness. The "on-the-spot" swab and DNA tests will help distinguish between Covid-19 and other seasonal illnesses, the government said. The health secretary said this would be "hugely beneficial" over the winter.

Currently, a third of tests take longer than 24 hours to process. The announcement comes as the government pushed back a July target to regularly test all care home staff and residents - a key move to identify so-called silent spreaders, those who are infected but do not show symptoms. This is unlikely to be achieved until September because the number of testing kits has become more limited. The government said almost half a million of the new rapid swab tests, called LamPORE, will be available from next week in adult care settings and laboratories, with millions more due to be rolled out later in the year. Additionally, thousands of DNA test machines, which have already been used in eight London hospitals and can analyse nose swabs, will be available across NHS hospitals from September.

Around 5,000 machines, supplied by DnaNudge, will provide 5.8 million tests in the coming months, the Department for Health said. There is currently no publicly available data on the accuracy of the new tests. But Sir John Bell, Regius Professor of Medicine at Oxford University, who has been advising the government on tests, said they produced the same "sensitivity" as the current lab-based tests. The breakthrough on testing is important for a number of reasons - not just because one has the ability to test for flu and other viruses too. Firstly, speed. The fact the tests do not have to be sent off to a lab means the processing times are much quicker. In hospital, most tests - 9 in 10 - are currently turned around in 24 hours. But those done in the community via regional drive-through centres, using postal kits and mobile units, tend to take longer because they have to be sent away to labs for processing...

Serological SARS-CoV-2 assays are needed to support clinical diagnosis and epidemiological investigations. Recently, assays for the large-volume detection of total antibodies (Ab) and immunoglobulin (Ig) G and M against SARS-CoV-2 antigens have been developed, but there are limited data on the diagnostic accuracy of these assays. This study was organized as a Danish national collaboration and included fifteen commercial and one in-house anti-SARS-CoV-2 assays in sixteen laboratories. Sensitivity was evaluated using 150 serum samples from individuals diagnosed with asymptomatic, mild or moderate nonhospitalized (n=129) or hospitalized (n=31) COVID-19, confirmed by nucleic acid amplification tests, collected 13-73 days from symptom onset. Specificity and cross-reactivity were evaluated in samples collected prior to the SARS-CoV-2 epidemic from > 586 blood donors and patients with autoimmune diseases or CMV or EBV infections. Predefined specificity criteria of ≥99% were met by all total-Ab and IgG assays except one (Diasorin/LiaisonXL-IgG 97.2%).

The sensitivities in descending order were: Wantai/ELISA total-Ab (96.7%), CUH/NOVO in-house ELISA total-Ab (96.0%), Ortho/Vitros total-Ab (95.3%), YHLO/iFlash-IgG (94.0%), Ortho/Vitros-IgG (93.3%), Siemens/Atellica total-Ab (93.2%), Roche-Elecsys total-Ab (92.7%), Abbott-Architect-IgG (90.0%), Abbott/Alinity-IgG (median 88.0%), Diasorin/LiaisonXL-IgG (84.6%), Siemens/Vista total-Ab (81.0%), Euroimmun/ELISA-IgG (78.0%), and Snibe/Maglumi-IgG (median 78.0%). The IgM results were variable, but one assay (Wantai/ELISA-IgM) had both high sensitivity (82.7%) and specificity (99%). The rate of seropositivity increased with time from symptom onset and symptom severity.

In conclusion, predefined sensitivity and specificity acceptance criteria of 90%/99%, respectively, for diagnostic use were met in five of six total-Ab and three of seven IgG assays.

Preprint of the study available at medRxiv (August 2, 2020):

https://doi.org/10.1101/2020.07.30.20165373