This archive report was first published on 15 June 2020.
As the world grapples with the COVID-19 pandemic, understanding the different types of coronavirus tests available is crucial in determining when and who to examine.
Published on June 15, 2020, by Fawzia Rasheed, El-Nasir Lalani, and Gijs Walraven, this article aims to answer common questions about coronavirus testing.
According to the authors, Covid-19 symptoms typically show around five-six days after infection, but can take as long as two weeks. Those carrying the virus can infect others before and after symptoms show, and antibodies are produced quite late in infection — from the second week onwards and well after first symptoms appear.
There are different ways to assume someone was or is infected, including using clinical symptoms, antibody tests, and virus tests. Using clinical symptoms is the most widespread method, but it has drawbacks, such as missing detecting infection in people with mild or few symptoms, which could happen in as many as 80 per cent of cases.
Antibody tests, which detect the human response to infection, are also available, but some are unreliable. These tests are useful in providing an indication of the extent of infection in groups of people or by area, but they do not predict whether or not someone is immune, or how long their immunity might last.
Tests that detect components of the SARS-CoV-2 virus are definitive and tell you if someone is infected. These tests are accurate, but they can fail to detect those with low levels of virus. They generally use nasal swabs, but will likely also soon include saliva, blood, and possibly stool samples.
When these tests become more feasible, they will be particularly useful in limiting infection spread as they detect the virus early in infection in people before symptoms show. Importantly, they also detect infection in those without symptoms who may never otherwise suspect they are infected.
The authors recommend reviewing the latest national guidelines and the World Health Organisation's information on specific tests. They also emphasize the importance of knowing what to expect, including the need for consent, pre and post-test counselling, and the logistics of contact tracing and quarantine.
El-Nasir Lalani is a professor working in laboratory and translational medicine and the founding director of the Aga Khan University Centre for Regenerative Medicine and Stem Cell Research. Gijs Walraven is the director for Health of the Aga Khan Development Network and general manager of the Aga Khan Health Services.
