Ireland's One Dimensional Approach to Testing is Failing

In this paper, Michael Mina and Kristian Anderson argue that we have developed a blinkered approach to COVID-19 testing. We are viewing testing purely from a diagnostic perspective, and this narrow definition of the purpose of testing has confined us to a limited set of policy options, with predictable consequences for our public health outcomes.

Diagnostic, surveillance, and screening are three distinct approaches to testing, each requiring their own instruments and implementation strategies, and offering different insights and opportunities. Fortunately, we do not have to choose between them. When we combine testing approaches, we multiply their powers and give ourselves a more powerful toolkit with which to control this outbreak.


Figure 1 - Three Different Approaches to Testing

Source: Michael J. Mina, and Kristian G. Andersen Science 2021;371:126-127

Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.


Diagnostic

A diagnostic test are used to determine the nature of the assess an individual’s condition with the goal of reaching a diagnosis. A patient presents with symptoms and the physician performs a diagnostic test to determine their condition and the care they will receive. Diagnostics are focused on the individual and only test sensitivity matters. The RT-PCR process can detect trace amounts of genetic material in its samples, giving patients and clinicians confidence in its results, whether positive or negative. The high sensitivity of the PCR test makes it an excellent diagnostic test for COVID-19, but there are other roles for testing during a pandemic.


Surveillance

Surveillance testing can detect and measure the prevalence of a disease in the population, with the ultimate goal of informing public health policy. Surveillance testing can be used to understand past exposures and spread of the disease (e.g. serological testing) but it can also measure ongoing transmission. For example, testing sewage and wastewater in a geographic area can tell policymakers if the disease is still spreading in the local community. From there, they can develop more informed and targeted policy responses.


Screening

The goal of the screening approach is to prevent onward transmission of the virus by finding asymptomatic individuals in the population (symptomatic individuals are expected to put themselves forward for testing). Screening can also detect pre-symptomatic individuals, as well as those who are unaware or unconcerned that they are displaying symptoms.


Public health screening is potentially the most powerful form of COVID-19 testing, aimed at outbreak suppression through maximising detection of infectious individuals. This type of screening entails frequent serial testing of large fractions of the population, through self-administered at-home rapid tests, or in the community at high-contact settings, such as schools and workplaces

Fast, cheap, easy to administer tests can be used in a wide range of situations. Children can take tests in the morning before school, as their parents can before going to work. People can take a test while they wait to enter a shopping centre, a restaurant, a salon, or a gym. Guests can take tests before a wedding, or mourners before a funeral. The frequency of testing within the regimen, and its broad and decentralised application, compensates for the lower sensitivity of the test itself. As shown below, it doesn't require anything like100% adherence from the public to be effective.


Figure 2 - Public Health Screening to End Transmission

Explanation: When tests can be used frequently for screening and positive results followed up with subsequent isolation or adoption of enhanced activities to prevent onward transmission, an outbreak can change from exponential growth to decay by driving the reproductive number of the virus below one. Importantly, a successful public health screening program does not require full participation nor perfection in the public health screening tests. Here, even with 50% of individuals choosing not to participate (red points), an additional 10% of tests failing to stop onward transmission, and tests being used by participating individuals every 3 days, case counts can be turned around from rising to falling cases in one week and population incidence can drop rapidly. The frequency of testing and the fraction of the community participating can be tuned based on the desired targets to gain control of the outbreak.

 

The ultimate goal of the screening approach is to prevent onward transmission in the community, not to diagnose individuals for treatment. Preventing transmission is central to ending the outbreak and screening is one of the most promising tools available to us, yet few countries have chosen to take this approach. The authors note Vietnam, Ghana, and Senegal as exceptions. The approach adds a layer of screening on top of our diagnostics and it takes the pressure off our contact tracing system, leading to a more efficient use of our public health resources. If Ireland can build a stockpile of rapid testing resources and distribute them across the country, we will take a big step towards the elimination of COVID-19 on the island of Ireland.

Why has no one in the government, NPHET, or the HSE invested in rapid testing capacity? Why is rapid testing not part of the national conversation? Why are the media not asking the questions?