• Susanna Lehtimaki

COVID testing: a summary of practice in selected countries

Updated: Apr 13

Lack of surveillance testing prevents an understanding of the extent to which the virus is already spread among populations. Evidence shows that a high proportion of cases (50-78%)1,2 remain asymptomatic, suggesting that large parts of the population may be exposed to the virus without ever knowing it.


WHO recommends testing for the SARS-CoV-2 virus in order to isolate those infected and trace and test contacts.3,4 Thus far, most countries have tested less than one percent of their population and, limited by their testing capacity, reagents and PPE, have prioritized health care workers, those with severe symptoms and to some extent, high risk groups, i.e. the elderly and people with comorbidities. Only a few countries, such Germany 5 and Norway 6, have tested a larger share of their population. Iceland, a small island of 364,000 people, has tested around seven percent of its population – second only to the Faroe Islands, an autonomous territory of Denmark with a population 61,000 7 – with support from a private genetics company conducting screening among the general and non-symptomatic population.8,9


Given that with the current PCR testing only active viral infections can be detected, countries are now planning to expand testing to track immunity (see annex). While development of antibody tests takes time, companies are competing to get to the market: as of 7 April, there are currently at least 200 tests being used globally to identify antibodies to SARS-CoV-2 available or in development.10


Tests developed in a short period of time and based on only a few hundred samples, may not provide reliable results. There are sensitivity and specificity concerns associated to these tests, including related to false positives resulting from immunity to other coronaviruses. 11 False negative rates can also be high, because the test detects antibodies that may take 2-3 weeks for human body to develop and it is not yet known how long the immunity to the virus lasts.11’12 Despite all these concerns, tests are being rolled out without any of the normal review of reliability; sensitivity or specificity tests are not yet systematically assessed by the FDA 13 or equivalent agencies.14


Some countries, including Sweden, Finland, Germany and the UK are planning to conduct serological testing in limited number of people to assess the spread of the virus through the population. In addition to surveillance, the testing will provide valuable research data: for example on feasibility of home testing is in epidemics (Sweden), 15 and duration of immunity for the SARS-CoV-2 virus (Finland).16 However, the reports from countries indicate that the initial results will be available only in the end of April at earliest.15’16


While some countries 17 have begun to think of tests as a means to given individuals assurance about whether or not they have been infected ("immunity passports"), given the uncertainties related to sensitivity and specificity, this may not yet be appropriate. Instead tests may at best serve as a tool for surveillance at the population level to help assess the extent of viral transmission in a particular community or region. However, issues around reliability and delays reported in processing results in many countries may hamper usefulness for real time decision making around whether to extend current suppression measures.


References

  1. Day M. Covid-19: four fifths of cases are asymptomatic, China figures indicate. BMJ. 2020;2020(369). doi:10.1136/bmj.m1375

  2. Day M. Covid-19: identifying and isolating asymptomatic people helped eliminate virus in Italian village. BMJ. 2020;2020(368). doi:10.1136/bmj.m1165

  3. WHO. Laboratory Testing Strategy Recommendations for COVID-19. Geneva: WHO; 2020. https://apps.who.int/iris/bitstream/handle/10665/331509/WHO-COVID-19-lab_testing-2020.1-eng.pdf.

  4. WHO. WHO Director-General’s opening remarks at the media briefing on COVID-19 - 16 March 2020. https://www.who.int/dg/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19---16-march-2020. Published March 16, 2020.

  5. Robert Koch Institut. Aktueller Lage-/Situationsbericht des RKI zu COVID-19. https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/Gesamt.html. Published April 6, 2020. Accessed April 6, 2020.

  6. Norwegian Institute of Public Health. Daily reports about coronavirus disease (COVID-19). https://www.fhi.no/en/id/infectious-diseases/coronavirus/daily-reports/daily-reports-COVID19/. Published April 6, 2020. Accessed April 6, 2020.

  7. Boffey D. Veterinary scientist hailed for Faroe Islands’ lack of Covid-19 deaths. Guardian. https://www.theguardian.com/world/2020/apr/08/vetinary-scientist-hailed-faroe-islands-lack-covid-19-deaths. Published April 8, 2020. Accessed April 8, 2020.

  8. Government of Iceland. Large scale testing of general population in Iceland underway. https://www.government.is/news/article/?newsid=f96a270c-66e8-11ea-945f-005056bc4d74. Published March 15, 2020. Accessed April 4, 2020.

  9. The Directorate of Health, Iceland. COVID-19 in Iceland – Statistics. https://www.covid.is/data. Published April 6, 2020. Accessed April 7, 2020.

  10. The Foundation for Innovative New Diagnostics (FIND). SARS-COV-2 diagnostics pipeline. Immunoassays. https://www.finddx.org/covid-19/pipeline/?section=immunoassays#diag_tab. Published April 7, 2020. Accessed April 7, 2020.

  11. ECDC. An overview of the rapid test situation for COVID-19 diagnosis in the EU/EEA. Technical report. https://www.ecdc.europa.eu/sites/default/files/documents/Overview-rapid-test-situation-for-COVID-19-diagnosis-EU-EEA.pdf. Published April 1, 2020. Accessed April 7, 2020.

  12. Zhao J, Yuan Q, Wang H, Liu W, et al. Antibody responses to SARS-CoV-2 in patients of novel coronavirus disease 2019. Clin Infect Dis. 2020(28 Mar):ciaa344. doi:10.1093/cid/ciaa344

  13. New York City Health. SARS-CoV-2 Antibody Testing. https://www1.nyc.gov/site/doh/covid/covid-19-providers.page. Published April 6, 2020. Accessed April 6, 2020.

  14. O’Caroll L. UK risks losing offer of 400,000 Covid-19 testing kits a week. Guardian. https://www.theguardian.com/world/2020/apr/04/uk-risks-losing-offer-of-400000-covid-19-testing-kits-a-week. Published April 4, 2020. Accessed April 7, 2020.

  15. Larsson P & Callahan D. Researchers sending out home test kits to identify spread of COVID-19 antibodies in Stockholm. https://www.kth.se/en/aktuellt/nyheter/1-000-stockholmare-testas-for-corona-i-pask-1.973722. Published April 7, 2020. Accessed April 9, 2020.

  16. Terveyden ja Hyvinvoinnin Laitos. THL tutkii koronaviruksen leviämistä väestössä vasta-ainetutkimuksella – tutkimukseen kutsutaan osallistujia satunnaisotannalla. https://thl.fi/fi/-/thl-tutkii-koronaviruksen-leviamista-vaestossa-vasta-ainetutkimuksella-tutkimukseen-kutsutaan-osallistujia-satunnaisotannalla. Published April 7, 2020. Accessed April 8, 2020.

  17. Department of Health & Social Care, the Government of the United Kingdom. Coronavirus (COVID-19): scaling up our testing programmes. Policy paper. https://www.gov.uk/government/publications/coronavirus-covid-19-scaling-up-testing-programmes/coronavirus-covid-19-scaling-up-our-testing-programmes. Published April 6, 2020. Accessed April 7, 2020.


Annex. Summary of testing in selected countries



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