key: cord-1037743-l147b7jk
authors: Freudenthal, Bernard
title: Misuse of SARS-CoV-2 testing in symptomatic health-care staff in the UK
date: 2020-10-22
journal: Lancet
DOI: 10.1016/s0140-6736(20)32147-4
sha: 78547e557dc7373fc79b2e279c3704ef59579fe3
doc_id: 1037743
cord_uid: l147b7jk

nan

An initiative to screen asymptomatic health-care workers for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was timely and logical, 1 and contrasted markedly with the UK Government's testing strategy stated. [1] [2] [3] [4] [5] This misconception applies to both human and ruminant brains.

We declare no competing interests. 

About 1506-08, Leonardo da Vinci's studies of the brain culminated in fil ling the ventricles of an ox with melted wax, a pioneer accomplishment in medical science. An otherwise excellent review in The Lancet claimed that these drawings of the casted ventricles show the interventricular foramen of Monro and the paired lateral ventricles in a correct manner. 1 This misconception has repeatedly been stated in the literature. [2] [3] [4] We believe Leonardo neither did depict the two separate interven ricular foramina (often named after the erroneous description of Alexander Monro) 5 nor did he draw the two lateral ventricles properly. His drawing (figure C) renders an unpaired broad anterior part of the foremost ventricle. A single tube or channel connects it with the middle ventricle, and another single tube connects the middle one with the posterior ventricle, the latter representing the aqueduct. Leonardo then cut a midline section and opened the brain "like a book", 4 thus cutting both connecting tubes at least graphically in halves. The opened-out drawing can easily be folded together to prove this assumption (figure). Leonardo did not depict a transverse section, which would not halve the aqueduct and the other single tube in front, not to mention the third and fourth ventricle. The seemingly two lateral ventricles are in fact a single one cut in two halves.

Macroscopic anatomy and neuroimaging prove that a true midline section cannot show both lateral ventricles with their bilateral connec tions to the third ventricle. Leonardo must be credited for being the first to give a graphic representation of the connection between all the cerebral ventricles. However, he did not show their true anatomy. His opened-out presentation of a brain does not show the paired lateral ventricles and the foramen of Monro, as several authors erroneously down, and the way to do that is to get the amount of testing up". 2 This testing approach was then also applied to other groups of public sector workers. 3 The UK Government's approach of using SARS-CoV-2 testing as a strategy to reduce absenteeism rather than to increase the detection of otherwise asymptomatic spreaders was surely symptomatic of flawed analysis and misunderstanding of the utility of the SARS-CoV-2 pharyngeal swab RT-PCR test. WHO expressly advises against using this test as a rule-out in the event of negative results. 4 Sensitivity of the test might be as low as 83%, 5 and in our practice many colleagues believe it to be lower still. Overzealous redirection of self-isolating staff back to work before they had completed sufficient self-isolation to exclude infectivity was therefore likely to increase spread of the virus to other staff and to patients or care-receivers in a substantial number of cases, especially given the high prevalence and likelihood of SARS-CoV-2 infection among exposed health-care workers during the epidemic. Surely the only defensible policy would have been national opportunistic and frequent testing of NHS and social care sector staff regardless of symptomology, and the test should be used exclusively as a rule-in and not a rule-out test as per existing WHO guidance. 4 I declare no competing interests.

Robust epidemiological studies help detail asymptomatic spread. Results have been heterogeneous; assumptions vary between studies which might be subject to recall bias, definitions of symptoms are inconsistent, and some studies do not account for the critical presymptomatic phase of infection. Nonetheless, most such studies find evidence of asymptomatic SARS-CoV-2 transmission. 4 False-positive results can also limit HCW screening utility. They can be biological, with dead virus detected in non-infectious cases, and technical, where a test is positive in the absence of viral RNA. Regular screening risks identification of biological false positives; however, more research is required to understand the biology of persistent viral RNA shedding. Technical false positives might be reduced to manageable levels by testing in duplicate. 5 We believe a symptom-agnostic testing approach for SARS-CoV-2 among HCWs is an effective measure of reducing viral transmission. This approach is advocated on a population level 6 and might be particularly beneficial among HCWs given reports of hospitals acting as hotbeds of COVID-19.

Arguments against mass testing approaches previously have suggested a lack of resources might make this ineffective. However, UK daily testing capacity has increased tenfold since the publication of our Correspondence, 1 while rapid point-of-care antigen tests facilitate early intervention to limit transmission. 6 Screening for SARS-CoV-2 in asymp tomatic HCWs could be a vital weapon in the fight against COVID-19 now and over the winter months. This will help the National Health Service to maintain the capacity to treat other diseases in the face of a second wave. We must act to prevent further virus spread, economic disruption, and unnecessary death.

COVID-19: the case for health-care worker screening to prevent hospital transmission

Number of NHS doctors off sick 'may be nearly triple the official estimate

The Guardian. UK Covid-19 testing expanded to police, fire service and judiciary

Laboratory testing for coronavirus disease (COVID-19) in suspected human cases

Diagnosis of the Coronavirus disease (COVID-19): rRT-PCR or CT?

We thank Bernard Freudenthal for his response to our previous Correspondence. 1 We agree that use of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing among health-care workers (HCWs) solely to reduce absenteeism is inappro priate. Freudenthal correctly outlines the risks, posed by falsenegative results, of advising potentially infec tious HCWs to return to work. Moreover, staffing levels are currently far less problem atic within UK health-care settings than during the peak of the pandemic.HCW testing should aim to identify infectious cases and reduce nosoco mial transmission of SARS-CoV-2: testing only selfreported symptomatic cases risks missing many infectious cases. For instance, HCWs might unwittingly attend work with mild or non-specific symptoms. Furthermore, although the relationship between RT-PCR cycle threshold (Ct) values and infectivity requires further elucidation, evidence suggests that Ct values among asymptomatic and symptomatic cases are similar. 2 Crucially, viable virus has been isolated up to 6 days before symptom onset. 3