The Role of Testing in Deconfinement Policies

María Andreina Cantele

Oficial en la Dirección de Evaluación de Impacto y Aprendizaje de Políticas de CAF

This article was written by Maria Andreina Cantele, with the collaboration of Dilberth Cordero and Murilo Marins.

Most countries implemented confinement policies in an attempt to curb the rise in COVID-19 cases. However, the socio-economic impact has forced many governments to relax lockdown measures despite contagion risks.

A key factor in the success of deconfinement measures is the testing strategy. Its importance lies in the ability to break the chain of infection and measure the progression of the disease among the population.

What are the purposes of the different types of tests?

There are two main types of tests depending on the input they use to determine infection: viral tests and serology (or antibody) tests.

Viral tests: The SARS-CoV-2 virus is composed of an outer layer of proteins and a RNA nucleus; viral tests detect the presence of some of these elements in the body. This type of testing uses a nasopharyngeal (back of nose-throat) or oropharyngeal (back of mouth-throat) specimen collected with swabs following a standardized technique. The best known direct tests—also known as molecular tests—, and recommended by WHO, are the RT-PCR (reverse transcription polymerase chain reaction) tests. These are diagnostic tests that allow early detection.

Serology tests: When the immune system detects the presence of a virus, a sophisticated defense system is activated. One component is humoral immunity, in which specialized cells generate specific antibodies—also called immunoglobulins—to eliminate it. Using a blood sample, these tests determine the presence of such antibodies (IgM and IgG), which usually multiply a few days after the first symptoms. Serology tests, if performed at the right time, provide information on an ongoing (IgM) or past (IgG) infection, and thus, they can be used to determine the prevalence of a disease in a population and the relative time to achieve herd immunity.

What aspects should be considered to design a testing strategy?

Viral tests are key to isolating and breaking the chain of infection: Early detection and isolation are more effective in preventing future infections than other measures currently in place, such as international flight restrictions or social distancing measures. Therefore, applying viral tests is key to ensuring that deconfinement does not trigger new, longer waves of infection.

A promising strategy is pooled testing, as it helps reduce the number of tests needed to detect positive cases. This strategy involves taking samples of a group of people using a single test. If the result is negative, therefore, it is safe to say that no person in the group is infected; and if positive, they are divided into smaller groups and the test is re-applied on each sub-group until the infected subjects are identified. This test can be useful when applied to a group of people who have been in contact with infected persons or living in areas with high infection rates.

On the other hand, more research on antibody tests is required to increase their usefulness in the context of deconfinement: The information they offer is the presence of immunity, both individually and in a given population. Further insights are required, however, into the composition of the virus and our body’s response over time. Thus, immunity remains a mystery and we cannot rule out the possibility that people who have been infected in the past may catch the disease again.

In addition, deconfinement policies based on immunity tests to allow reactivation of economic activity, use of public spaces, or domestic and international mobility may bring about perverse incentives that lead to greater inequality and put more pressure on the healthcare system. For example, individuals who test negative will have incentives to become exposed in order to be able to resume these activities, posing an individual risk on their health and the system. Given the low percentage of the population with antibodies in cities with the largest outbreaks (Wuhan 10%, Nueva York 20%, Madrid 11% as of May), this does not seem to be right strategy.

What factors should be considered when choosing between tests?

There are elements that should be considered by decision makers, with critical trade-offs . First, the tests used to identify the presence of the virus have a margin of error that varies depending on the type of test, which ideally should be less than 10%. In addition, the costs and times to obtain the results also vary. Quick testing is often less expensive and with higher margins of error than tests that require longer processing time.

Below is a brief comparison of these aspects:

Viral tests: PCR tests have shown the narrowest margin of error when the subject begins to develop symptoms, but this margin increases as the infection progresses. Therefore, they are useful for diagnostic purposes, but are expensive and with long processing times. Antigen testing, on the other hand, is faster, but has a high margin of error as there is a high probability of false negatives (i.e., a test that was negative when the patient was actually infected).

Serology tests: They there are different test types in this category: qualitative and quantitative tests. The first are quick tests that determine the existence of each type of antibody. Quantitative tests also show the quantity of each antibody; in general, the latter have a narrower margin of error, but require more time to be processed.

Faced with current challenges, CAF has been supporting countries to mitigate the economic and social consequences in the region. Thus, through its Investment and Business Development Fund for Small and Medium-sized Enterprises (FIDE), it has implemented the Investment Program in Impactful Companies and Entrepreneurship in Response to COVID-19, which seeks to support solutions with short-term effect to counteract these challenges. These have included initiatives aimed at developing PCR pooled testing, first in Brazil with NEOPROSPECTA, and potentially in other countries. In addition, with humanitarian aid resources granted to Argentina, the national universities of San Martin (UNSAM) and Quilmes (UNQ) recently developed a span>rapid molecular test.

These concrete actions in improving access to tests for virus detection are yet another expression of CAF’s support to countries in mitigating the spread of the pandemic.