May 15, 2021

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Rapid tests and false negatives: Puerto Rico and Peru's strategies against COVID-19

From the CPI

On April 26, the Peruvian citizen Miriam Grace presented the first symptoms of COVID-19: sore throat, accompanied by cough and fever. The alert was lit when, on May 2, his sister María del Carmen and his nephews Santiago and Antonella also registered their first symptoms, which ranged from nausea and vomiting to loss of taste and smell, according to official reports from the Ministry of Health of Peru and the interviews that the Center for Investigative Journalism and Ojo Público conducted with the family.

On May 4, Juan Francisco, father of Miriam and María del Carmen, fell ill with a recurring cough, and on Saturday, 9 of that month, the virus claimed the only fatality in this family, who shared the same home in the Piura region, in northern Peru. Edith, who was the matriarch of this Piura family, died at home due to a COVID-19 infection, according to the death certificate.

Due to this death, the Ministry of Health of Peru went to the home of Edith to perform a rapid antibody test on the five people who had direct contact with her during the last days of her life. Only Miriam Grace, Juan Francisco and María del Carmen tested positive. Santiago and Antonella, who even presented the most characteristic symptoms of the virus, were registered as negative before the Peruvian State.

"Those are the most dangerous: false negatives," said Puerto Rican epidemiologist Andrés Juliá Beltrán, who oversees the COVID-19 situation in Yauco and Lajas, two towns in southern Puerto Rico, on the risk of serological or antibody tests. These tests do not detect the virus itself, but the antibodies that are present in our blood when we become ill with COVID-19, and that can take up to two weeks to appear after infection. Put another way, a person who is in an initial stage of the disease can test negative for an antibody test, even if he already has symptoms and is infected.

As in the case of Peru, Juliá Beltrán claimed to have several patients who have produced false negatives to the antibody test in Puerto Rico. He added that this presents a risk since these people often think that they do not have the virus when obtaining a negative result, and infect other people.

This was the case of a 50-year-old woman from the town of Ciales, who arrived to Puerto Rico from the US to visit his family in mid-May. He already had some symptoms of COVID-19, such as fever and cough, and his son had tested positive in the US Three days after flying to the island, an antibody test was performed and it was negative. A week later, the symptoms worsened and she was hospitalized. It was not until then that a molecular test was performed that was positive. One day after knowing the result of this test, the woman died.

In total, at least 17 infections of COVID-19 have been confirmed in this town from this case. It is the largest chain of transmission that has occurred in Puerto Rico from a traveler, according to epidemiologist Luis Mayol, who leads the epidemiological response of Ciales, a town in the center of the island. As of August 7, this town registered a total of 73 patients with this new strain of the coronavirus.

Molecular tests do not detect antibodies, but rather the presence of the virus. Although they can also give false results if they are carried out on the same day that the infection occurs or when the person has been infected for a long time, they have proven to be the most accurate.

 COVID Photo by Eric Rojas | Investigative Journalism Center Test administration service station in San Juan, Puerto Rico

Almost a dozen epidemiologists and salt experts you interviewed recommend that the contagion of a person always be confirmed using a molecular test, the only test recommended by the World Health Organization (WHO) to confirm that a person has COVID-19. At the United States level, the Federal Food and Drug Administration (FDA) also allows antigen testing that detects virus material for diagnosis. Antibody or serological tests must be complementary to molecular tests as part of medical evaluation, or for research purposes, such as determining the prevalence of the virus in a community.

Most of the 52 countries in Latin America and the Caribbean have followed the recommendation of the WHO and directed their efforts to acquire and realize the greatest quantity possible from molecular testing. But Puerto Rico, Peru and Venezuela followed another route, prioritizing the use of the antibody test to identify COVID-19 in their population, according to an investigation by the Center for Investigative Journalism (CPI), in collaboration with the Peruvian environment Ojo Público .

In the case of Brazil, contrary to the recommendations of health experts, the country allows the use of antibody tests to confirm a diagnosis if they are performed when the person has had symptoms for at least seven days, according to protocol of the Brazilian Ministry of Health.

In the COVID-19 data reported by Ecuador, this mixes the serological tests in its total of cases confirmed, when they should only be those obtained through molecular testing.

Public policy error

Since March, several times a day and in different ways, a group of Puerto Rican scientists use as best they can the 280 characters that Twitter allows to monitor the response of the Government of Puerto Rico to the pandemic. One of their main complaints has been the misuse of antibody tests and the lack of urgency to increase molecular testing capacity. Not only did they let it be known on social media, but also in a letter to Governor Wanda Vázquez Garced, academic forums and interviews in the media.

“The test [de anticuerpos] does not tell you where it is. the virus. To control the pandemic, you need to know where the virus is and prevent contagion. You cannot prevent contagion when you are seeing what happened two weeks ago, ”said Mónica Feliú Mójer, doctor in neurobiology and professor at the University of California in San Francisco, referring to the time it takes for a person to develop antibodies after infection.

Despite this, countries like Puerto Rico, Peru and Venezuela bet on the serological test, or antibodies, as the spearhead to identify who had the virus. They have served as a diagnostic tool or as a filter to perform a molecular test, contrary to the recommendations of the experts.

Between April and May 2020, antibody tests represented around 50% of the total tests performed in Puerto Rico , according to the figures registered in the BioPortal, a platform of the Department of Health to centralize the information of the epidemic. This entity faces a delay in the reporting of serological tests. In July, said department continued adding the results of tests taken between April and June, according to the reports published by the agency.

In Peru, for its part, 73% of the more than 350,000 positive cases reported up to 20 July correspond to antibody tests. "Peru is the country that has made the most diagnoses with rapid tests" said this week the representative of the WHO in that country, Rubén Mayorga, in an interview with Peruvian media. In order to counteract this situation, in mid-July, the Pan American Health Organization donated supplies to the National Institute of Health of Peru to carry out 300 thousand molecular tests .

In Ecuador, although the Government states that it only uses molecular tests for diagnosis, it includes the positive results of the antibody tests in the total confirmed cases of COVID-19, according to the daily reports published by the Government. Of the 91,969 cases reported as of August 7, 10% correspond to antibody tests.

In the case of Brazil and Venezuela, both countries use molecular and antibody tests, but do not provide data on the tests they perform, therefore that the extent of antibody tests in the number of infections reported is unknown.

According to the United Nations Office for the Coordination of Humanitarian Affairs, the Venezuelan authorities reported a total of 697,691 tests to detect COVID-19 by May 21th. Of this figure, that entity estimates that only 16,577 were molecular tests, or 2%.

The Government of Venezuela recently announced that it will "progressively" change the diagnostic system of the PCR, but did not provide further details.

WHO and Johns Hopkins University report erroneous data

The WHO database reflects erroneous figures for Puerto Rico, Peru and Ecuador, which do not meet the definition of that same health entity as confirmed case. The same problem occurs with the dashboard from Johns Hopkins University, another benchmark in virus surveillance worldwide.

WHO has been showing as confirmed cases the figure total positive cases (molecular and mixed antibody) reported by Puerto Rico, Peru and Ecuador, instead of only those by molecular testing. This despite the fact that the three countries have separate information on daily molecular and antibody tests available.

WHO and Johns Hopkins University did not answer questions about the findings of this history.

6 In April, the Government of Peru announced that it began using rapid tests throughout the country . Since then, it has published a breakdown between rapid and molecular tests .

The Peruvian president Martín Vizcarra said that: "We have not wanted to add the results of the rapid tests to the molecular tests, which are the ones that we report every day, so not to generate any type of distortion "

But there has been distortion. This has led, for example, to an error in the positivity rate, an indicator that shows how many positives there are among all the tests that are performed. Peru calculates this number using both types of tests mixed, and not only the amount of molecular tests, as happens around the world.

Peruvians are third in the region in cases per million inhabitants, but only if the results of both tests, as occurs in the database of the WHO and Johns Hopkins University. By taking only confirmed cases with molecular testing, more than 10 countries would be above Peru. This does not mean that there are fewer infections in Peru, but rather that there is less certainty and visibility about the situation in real time, explained several of the experts consulted.

“The confirmed case is the one that is positive to COVID-19 tests with the test of the protein polymerase chain [PCR] ”, explained Dr. Marcos Espinal, director of communicable diseases of the Pan American Health Organization (PAHO), the satellite organization of the WHO in the Americas.

Although it is up to each country to decide how to use the tests it acquires in its battle against the coronavirus, the doctor confirmed that the vast majority of countries in the region follow the WHO recommendation.

Espinal He said that a team at PAHO reviews the data it receives from the different countries of the region. But the WHO continues to report erroneous data for Ecuador, Peru and Puerto Rico, despite the fact that the island has reported its segregated confirmed cases since June 10, according to WHO guidelines.

Puerto Rico began to use the definition of confirmed case from CDC and WHO two months after the CPI revealed that the confirmed cases reported by the Government included positive antibody test results, without having a positive molecular test to back it up. [19659042] San Juan ” src=”×1.png” class=”img lazyload img-responsive image-large” data-delcorte=”large”/>

“Definitely many things are being worked on that we have not done or that we have done wrong,” said then the Secretary of Health, Lorenzo González, admitting that the agency had to correct the definitions it uses, including the of confirmed cases.

Now the Government of Puerto Rico speaks of confirmed cases only through molecular tests. Those who test positive for antibodies are considered probable cases awaiting confirmation by a PCR test, according to the new protocol.

The Department of Health classified as “probable cases” only those patients with positive test results serological. However, according to the CDC a probable case may also include clinical criteria (for example, having symptoms or respiratory problems) and epidemiological evidence, among others.

Dr. Raúl Castellanos, coordinator of PAHO in Puerto Rico rejected a request for an interview.

Million dollar purchases of antibody tests

In mid-March, when most of the countries were concentrating their efforts on buying molecular tests, Puerto Rico and Peru opted to acquire large amounts of antibody tests to detect the virus in the population.

This despite the fact that these antibody tests were already under criticism in places like Europe due to their low effectiveness and validation problems.

In Puerto Rico, the Department of Health purchased more than 1.3 million antibody tests to detect the disease among the nearly three million residents on the island. Molecular testing took a back seat: the agency only purchased 50,000 kits from the Quest company, which added to the 10,000 molecular testing materials provided by the CDC during the first two months since cases were documented in Puerto Rico.


At the same time, in Peru, President Vizcarra announced the purchase of 1.4 million antibody tests and 10,000 molecular tests to diagnose COVID-19 . The acquisition of antibody tests responded, according to the official version, to a strategy of "fast pass" to detect those infected and stop the spread of the disease.

In total, the central government of the Peru has purchased more than 5.2 million antibody tests at a cost of 107.7 million soles, or nearly $ 30 million. Puerto Rico, which was about to disburse $ 38 million for a million of these tests but canceled the transaction amid irregularities, has allocated more than $ 9 million in over 350,000 antibody tests.

The purchase of this type of samples in the Island came as a recommendation from a group of doctors who advise the Government. Its low cost and relative availability compared to molecular tests were factors in this decision, two sources told the CPI.

The transactions were riddled with irregularities. More than a million samples never arrived and were paid at a premium, to people linked to the political party in power. For example: the Government of Puerto Rico bought 200,000 antibody tests for the brand, Orient Gene, at $ 26 each.

A day later, Peru obtained the same test brand for less than $ 4.

In addition, there were complaints about false results due to the low effectiveness of these tests. Three of the four brands acquired by the Government of Puerto Rico were withdrawn from the market as they were not approved by the FDA: Phamatech, Novatest and more recently, Clarity.

 San Juan

There was also debate on the acquisition of this type of evidence. The former head of the National Institute of Health, Ernesto Bustamante, criticized the purchase of antibody tests for their low effectiveness and false results due to the time it takes for a person to generate antibodies to COVID-19.

A At the end of March, the Ministry of Health (Minsa) of Peru assured that the antibody tests would be complementary to the molecular ones and for epidemiological surveillance. In contrast, the medical committee that advises the Minsa said something different : antibody tests would be used for diagnosis in symptomatic people after six days have elapsed since the onset of symptoms.

April, Peru revised its protocols to make it clear that antibody tests would be used only for epidemiological surveillance purposes, particularly to identify asymptomatic persons.

Antibody tests have a purpose

“ If I want to complement my diagnosis and know how long each patient that I already did molecular tests has been infected with, it works. If I want to know if it's time to start loosening measures [de confinamiento]it works. If I want to know what percentage of my population got sick, it works. If I want to know in which region there were more cases or where the virus circulated more, it works ", explained Thalía García Telléz, a Mexican doctor based in Paris, and a specialist in immunology and infectious diseases.

" Its main function is not to diagnose to the patient, but to evaluate the behavior of the pandemic, "said Peruvian epidemiologist Cristián Díaz, who is in charge of health intelligence work in the Lambayeque region, in northern Peru, one of the most affected by the pandemic in that country.

 COVID Andina

García Telléz warned that administering antibody tests to the population as if they were diagnostic causes that there is no real-time information on the state of infection. He added that countries can use this type of test when they begin to lift confinement measures and health systems are no longer saturated, as a tool that allows them to see the behavior of the virus at the community level.

This is what happens. in different Latin American countries, as they begin to explore the reopening of their economies. Serological tests have been a useful tool to know, for example, the behavior of the virus in communities or social groups through “serological surveys.”

Argentina began to carry out antibody tests in the Buenos Aires subway stations, while Uruguay carries out random samples in rural schools that have begun to open. In the Dominican Republic, they have carried out operations in some neighborhoods with antibody tests to identify probable cases of the virus in asymptomatic people.


None of these countries has used antibody tests to confirm cases of COVID-19. [19659003] “Molecular tests allow identifying initial stages of infection and, therefore, they allow you to buy time to apply isolation measures. On the other hand, the serological one measures the early or late response of the immune system towards the virus ”, explained the Peruvian epidemiologist Edward Mezones, who is a member of the National Scientific Committee of the Medical College of Peru. "In the clinical space, which is the management of patients, the number of days of symptoms defines which test to use," he concluded.

Molecular ones are the " gold standard " of the Caribbean and other regions [19659020] In the Caribbean, all the islands only use molecular tests such as the “ gold standard ” for the diagnosis of the disease, but they have faced challenges in the processing of the tests, since all are sent to be processed to the Caribbean Public Health Agency (CARPHA, in English) in Trinidad & Tobago.

The Island of Saint Martin, for example, reported that they used complementary serological tests to find out if the person had immunity to the virus. Others like the US Virgin Islands do not include antibody test results in their daily reports. US Territory epidemiologist Esther Ellis said that serologic tests "only indicate past infections and are not comparable with data from (molecular) PCR tests."

"We keep the antibody test tract in a separated. Our confirmed cases are positive results to PCR tests. All tests are done in the territory unless a private provider sends them off the island to a commercial laboratory like LabCorp, ”he said in written statements.

Worldwide, some of the challenges in getting molecular tests include the price, processing lead time, and shortage of materials such as swabs and vial transportation required to collect the sample. Only a handful of companies control the supply of molecular tests in the hemisphere: Abbott, Thermo Fisher, Roche, Cepheid, LabCorp and Quest (the latter mainly in the United States and Puerto Rico).

The circumstances between countries are different. Peru, Ecuador and Brazil have faced limitations in obtaining the necessary amount of molecular tests while accumulating a higher rate of confirmed cases than Puerto Rico (2,571). Cariocas lead with a rate of 13,505 cases, followed by Ecuador with 4,827 and Peru with 3,737.

In the case of Peru, epidemiologists Cristián Díaz, Edward Mezones and Manuel Loayza agreed that until the beginning of July, the The government chose to use a greater number of antibody tests because the use of molecular tests implied logistics, trained personnel and decentralized resources that the country does not have.

In some regions of the country, such as Piura, there is only one molecular biologist to process molecular tests, so most of them were sent to the capital. This has limited the processing capacity.

“Even if we had kits and implements for a million people, logistically it would not have been possible, because we do not have the technology for analysis [de moleculares] in all regions. The rapid test, for its part, is a drop of blood that can be taken in field work, it takes 15 minutes. The reasons for using it were quite obvious, "said Díaz, who heads the health intelligence office of the Lambayeque Assistance Network, in northwestern Peru.

And while Peru was struck down by the virus, the Government of Puerto Rico claimed to maintain the epidemic under control and made no effort to acquire more molecular evidence. The excuse was always the same: there is a global shortage.

"Although there are other places that have had similar challenges, they have had the will and creativity to see how they deal with the problem," said Dr. Feliú Mójer. [19659003] Given the lack of inputs for molecular tests, Uruguay, for example, went early in the emergency to the State University to create its own kits . The country was able to stop the infections through molecular tests.

The journalists Freeman Rogers (BVI) contributed to the data collection for the maps of this story; Tomer Urwicz and Tatiana Oviedo (Uruguay); Shari Avendaño and Katherine Pennacchio (Venezuela); Isabela Ponce (Ecuador); Gabriel Diez and César Sánchez (Bolivia); Alejandra Thais, Milagros Berríos and Iana Málaga (Peru); Ian Cavazos and Guillermo Flores (Mexico); Monserrat Saavedra and Ignacia Velasco (Chile); Fernando Silva (Honduras); Mariela Mejía and Laura Rodríguez Saba (Dominican Republic); Mary Triny Zea (Panama); Irene Rodríguez and Armando Mayorga (Costa Rica); Carla Miranda (Brazil); Widlore Merancourt (Haiti); Elaine Díaz, Darcy Borrero Batista and Yohan Amed Rodríguez Torres (Cuba); Efrén Lemus (El Salvador); Ángel Mazariegos Rivas and Lucía Ixchíu (Guatemala); Julián Navarrete (Nicaragua); Micaela Cattaneo and Juliana Quintana (Paraguay); María Tula and Emiliano Suárez (Argentina).

This story is published in Metro thanks to an alliance with the CPI, you can access the original note HERE

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