The value of university screening is unknown
The value of mass testing for evidence of SARS-CoV-2 viral material in people without any symptoms of infection is unknown. Targeted testing, of those with highest chance of infection based on predictive symptoms or known contact with a confirmed case, with active support for isolation of confirmed cases, has a far stronger evidence base. Testing those who pose highest risk to others e.g. health and care workers is also important. Yet screening is seen as heroic action against the virus, and is intuitively popular. Anyone who advises caution will be condemned as standing in the way of progress.
Screening involves searching the symptomless population with the aim of finding hidden infectious cases at the precise moment before they start spreading it to other people. It is like searching for needles that appear transiently in haystacks. A main difficulty is that we do not have a test of infectiousness. A negative result in a symptomless person is no guarantee that they are not currently, or soon to become, infectious, and a positive result in a symptomless person is no guarantee that they are infectious (1). Therefore testing of university students will create false reassurance and potential riskier behaviors when infectious people test negative, and unnecessary isolation and disruption to teaching when non-infectious people test positive.
There are numerous variables influencing the infection rate in university populations, and numerous multi-layered interventions being practiced to limit spread (2). Therefore, even though mass screening is likely to add little value, the universities that practice it will, no doubt, be lauded as having controlled their infection rates through screening. Handpicked examples will be used selectively to back a prior belief in screening’s value.
Cambridge University could have chosen to randomly allocate some college populations to be offered their nine week screening programme, and the rest to receive standard testing regimes. Cases of serious illness, person-days of isolation, and other measures of disruption to university and citizen life, could have been measured. Probably, the study would be of inadequate power to test the hypothesis that screening does more good than harm, which does beg the question of why anecdotal evidence of a screening effect in universities is so readily accepted.
That USA universities are offering SARS-CoV-2 screening is no surprise, given their vastly different culture in relation to healthy person testing. Universal annual periodic checks became part of American life, and commerce, from the 1950s (3), and attempts to advocate for an evidence-based approach to screening policy and delivery have, ever since, met with fierce resistance (4).
That a small handful of UK universities are following the USA approach, without robust evaluation, is disappointing, however well intentioned. Large companies in the UK frequently offer health screening as a ‘perk’ to their employees even when harm is likely to outweigh benefit. Universities are large businesses, but one would have hoped that the hard-won struggle to achieve sound assessment of health technologies might have had more influence on them (5). Conflation of the issue of mass testing with the legitimate use of pooled sampling simply diverts attention from the fact that mass testing is not recommended by SAGE (6) and is likely to divert resources, cause some harm, and achieve little benefit.
For thirty years of my career I worked, with others, to achieve ethical and best value approaches to UK health screening (7). Blind faith in medical technology coupled with the covert, skillful, and highly aggressive marketing strategies enacted on behalf of the diagnostics and pharmaceutical industries always made this an uphill struggle. It would be a great shame if the chaos of the pandemic led us to abandon ethical principles of ‘first do no harm’, autonomy and informed choice, and to dismantle our hard-won regulatory frameworks aimed at evidence based policy making and robust health technology assessment (8).
1. Raffle, A.E., Pollock, A.M., Harding-Edgar, L. (2020) Covid-19 mass testing programmes should be modelled on successful screening programmes. BMJ 2020;370:m3262 doi: https://doi.org/10.1136/bmj.m3262
2. Brooks-Pollock, E., Christensen, H., Trickey A., et. al. (2020) High COVID-19 transmission potential associated with re-opening universities can be mitigated with layered interventions. medRxiv 2020.09.10.20189696; doi:https://doi.org/10.1101/2020.09.10.20189696
3. Han, P.K. (1997) Historical changes in the objectives of the periodic health examination. Annals of Internal Medicine 127, 910–917.
4. Fletcher, S.W. (1997) Whither scientific deliberation in health policy recommendations? Alice in the Wonderland of breast-cancer screening. New England Journal of Medicine 336, 1180–1183.
5. Hogarth, S., Löblová, O. Regulatory niches: Diagnostic reform as a process of fragmented expansion. Evidence from the UK 1990–2018. Social Science and Medicine (in press)
6. Multidisciplinary Task and Finish Group on Mass Testing Consensus Statement for the Scientific Advisory Group on Emergencies (SAGE). 31 August 2020. https://www.gov.uk/government/publications/tfms-consensus-statement-on-m... (accessed 7 October 2020)
7. Raffle, A.E. Mackie, A. Gray, J.A.M. Screening; Evidence and Practice. 2nd edition. Oxford University Press. June 2019.
8. Deeks J. J, Brookes A. J, Pollock A. M. Operation Moonshot proposals are scientifically unsound BMJ 2020; 370 :m3699 doi: https://doi.org/10.1136/bmj.m3699
Competing interests: No competing interests