Testing: A Neglected, Critical Component of the COVID-19 Response

Throughout the COVID-19 pandemic, accurate and timely testing has been critical for diagnosis, disease surveillance, and containment strategies. Diagnostic capacity, however, has been a challenge for countries at all income levels, and has been further stressed by surges driven by new variants. Now, with promising oral therapeutics entering the market, diagnostics are even more crucial as they are integral to the roll-out and effective use of the new antivirals.

Not all tests are created equal

There are two different types of diagnostic tests that are most commonly used, each with its own strengths and weaknesses.

• PCR tests are the gold standard in testing. They have higher sensitivity and can often detect infection prior to symptoms appearing (as well as detecting infection in symptomatic individuals). However, these tests require analysis in laboratory facilities and there can thus be a lag of several days between test administration and provision of results.

• Rapid antigen tests (also called lateral flow tests) are self-administered, can be distributed at the community level, and provide results within 15 minutes without any need for laboratory analysis or trained health workers. However, these tests have a lower sensitivity than PCR tests and may not identify pre-symptomatic cases.

Each test has its value in different settings or public health strategies. Rapid tests are useful in helping presumed positive patients isolate from their communities and seek out confirmatory PCR testing. The ease of distribution, combined with the quick turnaround for results, also makes rapid tests a critical component of oral therapeutic strategies. PCR tests are useful for surveillance in high-risk settings, particularly when results can be delivered in a short timeframe. 

Rapid tests are commonly used in some places, such as in Europe. However, they are not widely used in many countries. For example, rapid tests are not yet widespread in Africa. Africa CDC has encouraged countries to scale up testing with rapid antigen tests and plans to launch a campaign of extensive rapid diagnostic testing.  

Diagnostic disparities threaten pandemic response

Striking inequalities remain for the number of tests administered in high-income countries in comparison to low- and middle-income countries. According to FIND, low- and lower-middle income countries (LMICs) account for only 21.7% of COVID-19 tests administered globally (but represent about 50% of the world’s population).

High-income countries conduct an average of 750 tests per 100,000 people each day; in most LMICs, the average is less than 50 tests per 100,000 people per day. The most recent iteration of the ACT-A budget and strategy sets a target minimum testing rate for LMICs of 100 tests per 100,000 people per day, double the current rate.

Data on testing from many LMICs are poor or reported infrequently, making it difficult to know the true depth of the disparities. Adding to the challenge is the lack of standard reporting across countries for how to track COVID-19 diagnostic tests. Additionally, data are often not disaggregated by test type and rapid tests are likely under-reported as they can be self-administered outside of standard medical systems.

Hurdles to scaling up testing capacity

Increasing availability of and capacity for diagnostic testing is a pressing issue globally, particularly as countries begin to plan for at-home oral antiviral treatments. It is essential that both PCR and rapid antigen tests are available in each country to contain the pandemic. Yet, for many countries this is a challenge.

For PCR testing, the health system must have adequate levels of trained health care personnel to administer and run the tests as well as labs with proper equipment to evaluate the tests and provide results in a timely manner. Testing sites must also be made readily available to people in all communities, which requires good distribution of resources throughout an entire country.  

Rapid tests do not have the same health system requirements and could be greatly beneficial in LMICs. This requires an adequate supply of tests in these countries that are made readily available, affordable and easy for individuals to access. Effectively rolling out these tests at scale has been a challenge, even in the United States. There are also concerns about underreporting of test results since they are taken at home and results must be self-reported to the health system.

A key constraint to scaling up testing capacity, particularly in LMICs, is funding. Without adequate funding it becomes difficult to achieve and sustain the testing capacity needed to employ a test-to-treat approach and monitor community outbreaks effectively. The ACT-A diagnostic pillar remained sorely underfunded in 2021. In its most recent budget for 2022, ACT-A estimates that it requires 7 billion USD for diagnostics, but it has yet to receive any pledges.

Scaling up testing requires a sense of urgency

Global and national leaders must give diagnostics the attention and prioritization it warrants. Actions must be taken to increase the availability of tests, scale-up capacity for conducting tests, and make tests easier to access in the community and at home. Donors need to provide greater investment towards scaling up testing, particularly rapid antigen testing.

Oral antivirals may take some time to become widely available, but we need to be using that time wisely by getting the testing capacity needed for test-and-treat strategies in place now. Countries and donors might look to examples of what has worked for testing of other diseases such as malaria, HIV, and tuberculosis. These existing programs and systems could even be leveraged or adapted to bring COVID-19 testing into communities.

The global response to date has been heavily focused on vaccines, which are a crucial tool to ending this pandemic. But if the experiences in the last year, and particularly with omicron, have taught us anything it is that we cannot vaccinate our way out of this crisis. We need a comprehensive global strategy with diagnostics and treatment as a core component. The combination of strong surveillance testing and test-and-treat strategies can help us transition out of this acute, emergency phase and contain the pandemic.