COVID-19 testing

The US CDC's COVID-19 laboratory test kit

COVID-19 testing can identify the SARS-CoV-2 virus and includes methods that detect the presence of virus itself (RT-PCR, isothermal nucleic acid amplification, antigen) and those that detect antibodies produced in response to infection. Detection of antibodies (serology) can be used both for diagnosis and population surveillance. Antibody tests show how many people have had the disease, including those whose symptoms were minor or who were asymptomatic. An accurate mortality rate of the disease and the level of herd immunity in the population can be determined from the results of this test. However, the duration and effectiveness of this immune response are still unclear, and the rates of false positives and false negatives must be duly factored into the interpretation.

Due to limited testing, as of March 2020 no countries had reliable data on the prevalence of the virus in their population. As of 24 May, the countries that published their testing data have on average performed a number of tests equal to only 2.6% of their population, and no country has tested samples equal to more than 17.3% of its population. There are variations in how much testing has been done across countries. This variability is also likely to be affecting reported case fatality rates, which have probably been overestimated in many countries, due to sampling bias.

Test methods

Explanation of the underlying pathophysiology pertaining to diagnosis of COVID19

There are two broad categories of test. Some look for the presence of the virus, e.g. the RT-PCR test. Others look for the antibodies which arise when a body is attacked by the virus. The purposes for which the test results are useful is different for the two kinds of test. Another option is to look for lung damage via either CT scan or low oxygen take up since testing via RT-PCR requires the virus to be established and there are a number of false negatives especially in the initial stages.

Current infection

Polymerase chain reaction

Polymerase chain reaction (PCR) is a process that causes a very small well-defined segment of DNA to be amplified, or multiplied many hundreds of thousands of times, so that there is enough of it to be detected and analyzed. Viruses such as SARS-CoV-2 do not contain DNA but only RNA. When a respiratory sample is collected from the person being tested it is treated with certain chemicals which remove extraneous substances and extract only the RNA from the sample. Reverse transcription polymerase chain reaction (RT-PCR) is a technique that first uses reverse transcription to convert the extracted RNA into DNA and then uses PCR to amplify a piece of the resulting DNA, creating enough to be examined in order to determine if it matches the genetic code of SARS-CoV-2. Real-time PCR (qPCR) provides advantages during the PCR portion of this process, including automating it and enabling high-throughput and more reliable instrumentation, and has become the preferred method. Altogether, the combined technique has been described as real-time RT-PCR or quantitative RT-PCR and is sometimes abbreviated qRT-PCR or rRT-PCR or RT-qPCR, although sometimes just RT-PCR or PCR is used as an abbreviation. The test can be done on respiratory samples obtained by various methods, including a nasopharyngeal swab or sputum sample, as well as on saliva. Results are generally available within a few hours to 2 days. The RT-PCR test performed with throat swabs is only reliable in the first week of the disease. Later on the virus can disappear in the throat while it continues to multiply in the lungs. For infected people tested in the second week, alternatively sample material can then be taken from the deep airways by suction catheter, or coughed up material (sputum) can be used. Saliva has been shown to be a common and transient medium for virus transmission and results provided to the FDA suggest that testing saliva may be as effective as nasal and throat swabs. The FDA has granted Emergency Use Authorization for a test that collects saliva instead of using the traditional nasal swab. It is believed that this will reduce the risk for health care professionals, will be much more comfortable for the patient, and will enable quarantined people to collect their own samples more efficiently. According to some experts it is too early to know the operating characteristics of the saliva test, and whether it will prove to be as sensitive as the nasopharyngeal swab test. Some studies suggest that the diagnostic value of saliva depends on how saliva specimens are collected (from deep throat, from oral cavity, or from salivary glands). A recent test conducted by the Yale University School of Public Health found that saliva yielded greater detection sensitivity and consistency throughout the course of infection when compared with samples taken with nasopharyngeal swabs.

• 
  Demonstration of a nasopharyngeal swab for COVID-19 testing
• 
  Demonstration of a throat swab for COVID-19 testing
• 
  A PCR machine

Isothermal amplification assays

There are a number of isothermal nucleic acid amplification methods that in principle work like PCR, amplifying a piece of the virus's genome, but are faster than PCR because they don't involve repeated cycles of heating and cooling the sample.

Antigen

An antigen is the part of a pathogen that elicits an immune response. While RT-PCR tests look for RNA from the virus and antibody tests detect human antibodies that have been generated against the virus (detectable days or weeks after the infection sets in), antigen tests look for proteins from the surface of the virus. In the case of a coronavirus these are usually proteins from the surface spikes, and a nasal swab is used to collect samples from the nasal cavity. One of the difficulties has been finding a protein target unique to SARS-CoV-2. There are related coronaviruses that cause the common cold.

Antigen tests are seen by many as the only way it will be possible to scale up testing to the numbers that will really be needed to detect acute infection on the scale required. Isothermal nucleic acid amplification tests, such as the test from Abbot Labs, can only process one sample at a time per machine. RT-PCR tests are accurate but it takes too much time, energy and trained personnel to run the tests. “There will never be the ability on a [PCR] test to do 300 million tests a day or to test everybody before they go to work or to school,” Deborah Birx, head of the White House Coronavirus Task Force, said on April 17. “But there might be with the antigen test.”

An antigen test works by taking a nasal swab from a patient and exposing that to paper strips that contain artificial antibodies designed to bind to coronavirus antigens. Any antigens that are present will bind to the strips and give a visual readout. The process takes less than 30 minutes, can deliver results on the spot, and doesn't require expensive equipment or extensive training.

The problem is that in the case of respiratory viruses often there is not enough of the antigen material present in the nasal swab to be detectable. This would especially be true with people who are asymptomatic and who have very little if any nasal discharge. Unlike the RT-PCR test, which amplifies very small amounts of genetic material so that there is enough to detect, there is no amplification of viral proteins in an antigen test. According to the World Health Organization (WHO) the sensitivity of similar antigen tests for respiratory diseases like the flu ranges between 34% and 80%. "Based on this information, half or more of COVID-19 infected patients might be missed by such tests, depending on the group of patients tested," the WHO said. Many scientists doubt whether an antigen test can be made reliable enough in time to be useful against Covid-19.

Medical imaging

Chest CT scans are not recommended for routine screening. Radiologic findings in COVID19 are not specific. Typical features on CT initially include bilateral multilobar ground-glass opacities with a peripheral or posterior distribution. Subpleural dominance, crazy paving, and consolidation may develop as the disease evolves.

• 
  Typical CT imaging findings
• 
  CT imaging of rapid progression stage

Past infection

Left: Automated analyzer for immunoassays, used, for example, to find SARS-CoV-2 antibodies. Right: Example of quantitative results for SARS-CoV-2 antibody test.

Serology tests rely on drawn blood, not a nasal or throat swab, and can identify people who were infected and have already recovered from Covid-19, including those who didn't know that they had been infected. Most serology tests are in the research stage of development.

Part of the immune response to infection is the production of antibodies including IgM and IgG. According to the FDA, IgM antibodies to SARS-CoV-2 are generally detectable in blood several days after initial infection, although levels over the course of infection are not well characterized. IgG antibodies to SARS-CoV-2 generally become detectable 10–14 days after infection although they may be detected earlier, and normally peak around 28 days after the onset of infection. Since antibodies are slow to present they are not the best markers of acute infection, but as they may persist in the bloodstream for many years they are ideal for detecting historic infections.

Antibody tests can be used to determine the percentage of the population that has contracted the disease and that is therefore presumed to be immune. However, it is still not clear how broad and how long and how effective this immune response is. As of April 2020 "[s]ome countries are considering issuing so-called immunity passports or risk-free certificates to people who have antibodies against Covid-19, enabling them to travel or return to work assuming that they are protected against reinfection". However, according to the World Health Organization as of 24 April 2020, “There is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection.” One of the reasons for the uncertainty is that most, if not all, of the current Covid-19 antibody testing done at large scale is for detection of binding antibodies only and does not measure neutralizing antibodies. A neutralizing antibody (NAb) is an antibody that defends a cell from a pathogen or infectious particle by neutralizing any effect it has biologically. Neutralization renders the particle no longer infectious or pathogenic. A binding antibody will bind to the pathogen but the pathogen remains infective; the purpose can be to flag the pathogen for destruction by the immune system. It may even enhance infectivity by interacting with receptors on macrophages. Since most Covid-19 antibody tests will return a positive result if they find only binding antibodies these tests cannot indicate that the person being tested has generated any NAbs which would give him or her protection against re-infection.

It is normally expected that if binding antibodies are detected the person also has generated NAbs and for many viral diseases total antibody responses correlate somewhat with NAb responses but this is not yet known for Covid-19. A study of 175 people in China who had recovered from COVID‑19 and had mild symptoms reported that 10 individuals had produced no detectable NAbs at the time of discharge, nor did they develop NAbs thereafter. How these patients recovered without the help of NAbs and whether they were at risk of re-infection of SARS-CoV-2 was left for further exploration. An additional source of uncertainty is that even if NAbs are present, several viruses, such as HIV, have evolved mechanisms to evade NAb responses. While this needs to be examined in the context of COVID-19 infection, past experiences with viral infection, in general, argue that in most recovered patients NAb level is a good indicator of protective immunity.

It is presumed that once a person has been infected his or her chance of getting a second infection two to three months later is low, but how long that protective immunity might last is not known. One study determined that reinfection at 29 days post-infection could not occur in SARS-CoV-2 infected rhesus macaques. Studies have indicated that NAbs to the original SARS virus (the predecessor to the current SARS-CoV-2) can remain active in most people for two years and are gone after six years. Nevertheless, memory cells including Memory B cells and Memory T cells can last much longer and may have the ability to greatly lessen the severity of a reinfection.

• 
  A PoCT being performed in Peru. A blood droplet is collected by a pipette.
• 
  Blood from pipette is then placed onto a COVID-19 rapid diagnostic test device.
• 
  The rapid diagnostic test shows reactions of IgG and IgM antibodies.

Infectivity

United States Centers for Disease Control and Prevention (CDC) updated the following information and recommendation in a "Decision Memo" on 3 May. At this time, data are limited regarding how long after infection people continue to shed infectious SARV-CoV-2 RNA, and can therefore still infect others. Key findings are summarized here.

1. Viral burden measured in upper respiratory specimens declines after onset of illness.
2. At this time, replication-competent virus has not been successfully cultured more than 9 days after onset of illness. The statistically estimated likelihood of recovering replication-competent virus approaches zero by 10 days.
3. As the likelihood of isolating replication-competent virus decreases, anti-SARS-CoV-2 IgM and IgG can be detected in an increasing number of persons recovering from infection.
4. Attempts to culture virus from upper respiratory specimens have been largely unsuccessful when viral burden is in low but detectable ranges (i.e., Ct values higher than 33-35)
5. Following recovery from clinical illness, many patients no longer have detectable viral RNA in upper respiratory specimens. Among those who continue to have detectable RNA, concentrations of detectable RNA 3 days following recovery are generally in the range at which replication-competent virus has not been reliably isolated by CDC.
6. No clear correlation has been described between length of illness and duration of post-recovery shedding of detectable viral RNA in upper respiratory specimens.
7. Infectious virus has not been cultured from urine or reliably cultured from feces; these potential sources pose minimal if any risk of transmitting infection and any risk can be sufficiently mitigated by good hand hygiene.

For an emerging pathogen like SARS-CoV-2, the patterns and duration of illness and infectivity have not been fully described. However, available data indicate that shedding of SARS-CoV-2 RNA in upper respiratory specimens declines after onset of symptoms. At 10 days after illness onset, recovery of replication-competent virus in viral culture (as a proxy of the presence of infectious virus) is decreased and approaches zero. Although persons may produce PCR-positive specimens for up to 6 weeks, it remains unknown whether these PCR-positive samples represent the presence of infectious virus. After clinical recovery, many patients do not continue to shed SARS-CoV-2 viral RNA. Among recovered patients with detectable RNA in upper respiratory specimens, concentrations of RNA after 3 days are generally in ranges where virus has not been reliably cultured by CDC. These data have been generated from adults across a variety of age groups and with varying severity of illness. Data from children and infants are not presently available.

Approaches to testing

A sample collection kiosk for COVID-19 testing in India

Timeline of Number of tests per million people in different countries.

After issues with testing accuracy and capacity during January and February, the United States was testing 100,000 people per day by 27 March. In comparison, several European countries have been conducting more daily tests per capita than the United States. Three European countries are aiming to conduct 100,000 tests per day – Germany by mid-April, the United Kingdom by the end of April and France by the end of June. Germany has a large medical diagnostics industry, with over 100 testing labs that provided the technology and infrastructure to enable rapid increases in testing. The UK sought to diversify its life sciences companies into diagnostics to scale up testing capacity.

In Germany, the National Association of Statutory Health Insurance Physicians said on 2 March, that it had a capacity for about 12,000 tests per day in the ambulatory setting and 10,700 had been tested in the prior week. Costs are borne by the health insurance when the test is ordered by a physician. According to the president of the Robert Koch Institute, Germany has an overall capacity for 160,000 tests per week. As of 19 March drive-in tests were offered in several large cities. As of 26 March, the total number of tests performed in Germany was unknown, because only positive results are reported. Health minister Jens Spahn estimated 200,000 tests per week. A first lab survey revealed that as of the end of March a total of at least 483,295 samples were tested and 33,491 samples (6.9%) tested positive for SARS-CoV-2.

By the start of April, the United Kingdom was delivering around 10,000 swab tests per day. It set a target for 100,000 per day by the end of April, eventually rising to 250,000 tests per day. The British NHS has announced that it is piloting a scheme to test suspected cases at home, which removes the risk of a patient infecting others if they come to a hospital or having to disinfect an ambulance if one is used.

In drive-through testing for COVID‑19 for suspected cases, a healthcare professional takes sample using appropriate precautions. Drive-through centers have helped South Korea do some of the fastest, most-extensive testing of any country. Hong Kong has set up a scheme where suspected patients can stay home, "[the] emergency department will give a specimen tube to the patient", they spit into it, send it back and get a test result a while after.

In Israel, researchers at Technion and Rambam Hospital developed and tested a method for testing samples from 64 patients simultaneously, by pooling the samples and only testing further if the combined sample is found to be positive. Pool testing was then adopted in Israel, Germany, South Korea, and Nebraska, and the Indian states Uttar Pradesh, West Bengal, Punjab, Chhattisgarh, and Maharashtra.

In Wuhan a makeshift 2000-sq-meter emergency detection laboratory named "Huo-Yan" (Chinese: 火眼, "Fire Eye") was opened on 5 February 2020 by BGI, which can process over 10,000 samples a day. With the construction overseen by BGI-founder Wang Jian and taking 5-days, modelling has show cases in Hubei would have been 47% higher and the corresponding cost of tackling the quarantine would have doubled if this testing capacity had not come into operation. The Wuhan Laboratory has been promptly followed by Huo-Yan labs in Shenzhen, Tianjin, Beijing, and Shanghai, in a total of 12 cities across China. By 4 March 2020 the daily throughput totals were 50,000 tests per day.

Open source, multiplexed designs released by Origami Assays have been released that can test as many as 1122 patient samples for COVID19 using only 93 assays. These balanced designs can be run in small laboratories without the need for robotic liquid handlers.

By March, shortages and insufficient amounts of reagent has become a bottleneck for mass testing in the EU and UK and the US. This has led some authors to explore sample preparation protocols that involve heating samples at 98 °C (208 °F) for 5 minutes to release RNA genomes for further testing.

On 31 March it was announced United Arab Emirates was now testing more of its population for Coronavirus per head than any other country, and was on track to scale up the level of testing to reach the bulk of the population. This was through a combination of drive-through capability, and purchasing a population-scale mass-throughput laboratory from Group 42 and BGI (based on their "Huo-Yan" emergency detection laboratories in China). Constructed in 14 days, the lab is capable of conducting tens of thousands RT-PCR tests per day and is the first in the world of this scale to be operational outside of China.

On 8 April 2020, In India, the Supreme Court of India ruled that private labs should be reimbursed at the appropriate time for COVID-19 tests However private labs have stated that they are unable to scale up the testing because of the price cap put on the testing and labs being forced to make advance payment to suppliers while they receive deferred payment from hospitals.

University of California San Francisco conducted PCR tests of 1,845 people in Bolinas, California on April 20–24, almost the entire town. No active infections were detected. Antibody testing was also performed but the results are not yet available.

Production and volume

Number of tests done per day in the United States.
Blue: CDC lab
Orange: Public health lab
Gray: Data incomplete due to reporting lag
Not shown: Testing at private labs; total exceeded 100,000 per day by 27 March

Different testing recipes targeting different parts of the coronavirus genetic profile were developed in China, France, Germany, Hong Kong, Japan, the United Kingdom, and the United States. The World Health Organization adopted the German recipe for manufacturing kits sent to low-income countries without the resources to develop their own. The German recipe was published on 17 January 2020; the protocol developed by the United States Centers for Disease Control and Prevention (CDC) was not available until 28 January, delaying available tests in the U.S.

China and the United States had problems with the reliability of test kits early in the outbreak, and these countries and Australia were unable to supply enough kits to satisfy demand and recommendations for testing by health experts. In contrast, experts say South Korea's broad availability of testing helped reduce the spread of the novel coronavirus. Testing capacity, largely in private sector labs, was built up over several years by the South Korean government. On 16 March, the World Health Organization called for ramping up the testing programmes as the best way to slow the advance of COVID‑19 pandemic.

High demand for testing due to wide spread of the virus caused backlogs of hundreds of thousands of tests at private U.S. labs, and supplies of swabs and chemical reagents became strained.

Available tests

PCR based

When scientists from China first released information on the COVID‑19 viral genome on 11 January 2020, the Malaysian Institute for Medical Research (IMR) successfully produced the “primers and probes” specific to SARS-CoV-2 on the very same day. The IMR's laboratory in Kuala Lumpur had initiated early preparedness by setting up reagents to detect coronavirus using the rt-PCR method. The WHO reagent sequence (primers and probes) released several days later was very similar to that produced in the IMR's laboratory, which was used to diagnose Malaysia's first COVID‑19 patient on 24 January 2020.

Public Health England developed a test by 10 January, using real-time RT-PCR (RdRp gene) assay based on oral swabs. The test detected the presence of any type of coronavirus including specifically identifying SARS-CoV-2. It was rolled out to twelve laboratories across the United Kingdom on 10 February. Another early PCR test was developed by Charité in Berlin, working with academic collaborators in Europe and Hong Kong, and published on 23 January. It used rtRT-PCR, and formed the basis of 250,000 kits for distribution by the World Health Organization (WHO). The South Korean company Kogenebiotech developed a clinical grade, PCR-based SARS-CoV-2 detection kit (PowerChek Coronavirus) approved by Korea Centers for Disease Control and Prevention (KCDC) on 4 February 2020. It looks for the "E" gene shared by all beta coronaviruses, and the RdRp gene specific to SARS-CoV-2.

In China, BGI Group was one of the first companies to receive emergency use approval from China's National Medical Products Administration for a PCR-based SARS-CoV-2 detection kit.

In the United States, the CDC distributed its SARS-CoV-2 Real Time PCR Diagnostic Panel to public health labs through the International Reagent Resource. One of three genetic tests in older versions of the test kits caused inconclusive results due to faulty reagents, and a bottleneck of testing at the CDC in Atlanta; this resulted in an average of fewer than 100 samples a day being successfully processed throughout the whole of February 2020. Tests using two components were not determined to be reliable until 28 February 2020, and it was not until then that state and local laboratories were permitted to begin testing. The test was approved by the FDA under an EUA.

US commercial labs began testing in early March 2020. As of 5 March 2020 LabCorp announced nationwide availability of COVID‑19 testing based on RT-PCR. Quest Diagnostics similarly made nationwide COVID‑19 testing available as of 9 March 2020.

In Russia, the first COVID‑19 test was developed by the State Research Center of Virology and Biotechnology VECTOR, production began on January 24. On 11 February 2020 the test was approved by the Federal Service for Surveillance in Healthcare.

On 12 March 2020, Mayo Clinic was reported to have developed a test to detect COVID‑19 infection.

On 18 March 2020, the FDA issued EUA to Abbott Laboratories for a test on Abbott's m2000 system; the FDA had previously issued similar authorization to Hologic, LabCorp, and Thermo Fisher Scientific. On 21 March 2020, Cepheid similarly received an EUA from the FDA for a test that takes about 45 minutes on its GeneXpert system; the same system that runs the GeneXpert MTB/RIF.

On 13 April, Health Canada approved a test from Spartan Bioscience. Institutions may "test patients" with a handheld DNA analyzer "and receive results without having to send samples away to a [central] lab."

Isothermal nucleic amplification

US President Donald Trump displays a COVID-19 testing kit from Abbott Laboratories in March 2020

On 27 March 2020, the FDA issued an Emergency Use Authorization for a test by Abbott Laboratories, called ID NOW COVID-19, that uses isothermal nucleic acid amplification technology instead of PCR. The assay amplifies a unique region of the virus's RdRp gene; the resulting copies are then detected with "fluorescently-labeled molecular beacons". The test kit uses the company's "toaster-size" ID NOW device which costs $12,000-$15,000. The device can be used in laboratories or in patient care settings, and provides results in 13 minutes or less. There are currently about 18,000 ID NOW devices in the U.S. and Abbott expects to ramp up manufacturing to deliver 50,000 ID NOW COVID-19 test kits per day.

All visitors to U.S. President Donald Trump are required to undergo the test on site at the White House.

In a study conducted by the Cleveland Clinic, the ID NOW COVID-19 test detected the virus only in 85.2% of the samples that contained it. According to the director of the study a test should be at least 95% reliable. Abbott said that the issue could have been caused by storing the samples in a special solution instead of inserting them directly into the testing machine.

Serology tests

As of 24 April, six tests had been approved for diagnosis in the United States, all under FDA Emergency Use Authorization (EUA). The tests are listed and described at the Johns Hopkins Center for Health Security. Other tests have been approved in other countries.

In the United States, as of 28 April, Quest Diagnostics made a COVID-19 antibody test available for purchase to the general public through the QuestDirect service. Cost of the test is approximately US$130. The test requires the individual to visit a Quest Diagnostics location for a blood draw. Results are available days later.

A number of countries are beginning large scale surveys of their populations using these tests. A study in California conducted antibody testing in one county and estimated that the number of coronaviruses cases was between 2.5 and 4.2% of the population, or 50 to 85 times higher than the number of confirmed cases.

In late March 2020, a number of companies received European approvals for their test kits. The testing capacity is several hundred samples within hours. The antibodies are usually detectable 14 days after the onset of the infection.

WHO Emergency Use Listing

Diagnostic tests accepted by the WHO for procurement

Date listed	Product name	Manufacturer
3 April 2020	Cobas SARS-CoV-2 qualitative assay for use on the cobas 6800/8800 Systems	Roche Molecular Systems
7 April 2020	Coronavirus (COVID-19) genesig rtPCR assay	Primerdesign
9 April 2020	Abbott Realtime SARS-CoV-2	Abbott Molecular
24 April 2020	PerkinElmer SARS-CoV-2 Real-time RT-PCR Assay	SYM-BIO LiveScience

As of 7 April 2020, the WHO had accepted two diagnostic tests for procurement under the Emergency Use Listing procedure (EUL) for use during the COVID‑19 pandemic, in order to increase access to quality-assured, accurate tests for the disease. Both in vitro diagnostics, the tests are genesig Real-Time PCR Coronavirus (COVID‑19) manufactured by Primerdesign, and cobas SARS-CoV-2 Qualitative assay for use on the cobas® 6800/8800 Systems by Roche Molecular Systems. Approval means that these tests can also be supplied by the United Nations and other procurement agencies supporting the COVID‑19 response.

Testing accuracy

In March 2020 China reported problems with accuracy in their test kits.

In the United States, the test kits developed by the CDC had "flaws;" the government then removed the bureaucratic barriers that had prevented private testing.

Spain purchased test kits from Chinese firm Shenzhen Bioeasy Biotechnology Co Ltd, but found that results were inaccurate. The firm explained that the incorrect results may be a result of a failure to collect samples or use the kits correctly. The Spanish ministry said it will withdraw the kits that returned incorrect results, and would replace them with a different testing kit provided by Shenzhen Bioeasy.

80% of test kits the Czech Republic purchased from China gave wrong results.

Slovakia purchased 1.2 million test kits from China which were found to be inaccurate. Prime Minister Matovič suggested these be dumped into the Danube.

Ateş Kara of the Turkish Health Ministry said the test kits Turkey purchased from China had a "high error rate" and did not "put them into use."

The UK purchased 3.5 million test kits from China but in early April 2020 announced these were not usable.

On 21 April 2020, the Indian Council of Medical Research has advised Indian states to stop using the rapid antibody test kits purchased from China after receiving complaints from one state. Rajasthan health minister Raghu Sharma on 21 April said the kits gave only 5.4 percent accurate results against the expectation of 90 percent accuracy.

Confirmatory testing

WHO recommends that countries that do not have testing capacity and national laboratories with limited experience on COVID‑19 send their first five positives and the first ten negative COVID‑19 samples to one of the 16 WHO reference laboratories for confirmatory testing. Out of the 16 reference laboratories, 7 are in Asia, 5 in Europe, 2 in Africa, 1 in North America and 1 in Australia.

Clinical effectiveness

Testing, followed with quarantine of those who tested positive and tracing of those with whom the SARS-CoV-2 positive people had had contact, resulted in positive outcomes..

Italy

Researchers working in the Italian town of Vò, the site of the first COVID‑19 death in Italy, conducted two rounds of testing on the entire population of about 3,400 people, about ten days apart. About half the people testing positive had no symptoms, and all discovered cases were quarantined. With travel to the commune restricted, this eliminated new infections completely.

Singapore

With aggressive contact tracing, inbound travel restrictions, testing, and quarantining, the COVID-19 pandemic in Singapore has proceeded much more slowly than in other developed countries , but without extreme restrictions like forced closure of restaurants and retail establishments. Many events have been cancelled, and Singapore did start advising residents to stay at home on 28 March, but schools reopened on time after holiday break on 23 March, even though schools did close moving to "full home-based learning" on 8 April.

U.S. aircraft carrier Theodore Roosevelt

After 94% of the 4,800 crew had been tested roughly 60 percent of the over 600 sailors who tested positive did not have symptoms.

Russia

On 27 April, Russia passed the 3 million test mark and had 183,000 people under medical supervision because they were suspected of having the virus with 87,147 people having tested positive for the virus and total confirmed deaths at 794. On 28 April Anna Popova head of Federal Service for Surveillance in Healthcare (Roszdravnadzor) in a presidential update stated that there were now 506 laboratories testing and that 45% of those tested have no symptoms with the number having pneumonia reducing from 25% to 20% and only 5% of patients with a severe form. 40% of infections were from family members. The speed of people reporting illness has improved from 6 days to the day people find symptoms. Antibody testing was carried out on 3,200 Moscow doctors and 20% have immunity.

Others

Several other countries, such as Iceland and South Korea, have also managed the pandemic with aggressive contact tracing, inbound travel restrictions, testing, and quarantining, but with less aggressive lock-downs. A statistical study has found that countries that have tested more, relative to the number of deaths, have much lower case fatality rates, probably because these countries are better able to detect those with only mild or no symptoms. A subsequent study has also found that countries that have tested more widely also have a younger age distribution of cases, relative to the wider population.

Research and development

A test which uses monoclonal antibodies which bind to the nucleocapsid protein (N protein) of the SARS-CoV-2 is being developed in Taiwan, with the hope that it can provide results in 15 to 20 minutes just like a rapid influenza test. The World Health Organization raised concerns on 8 April that these tests need to be validated for the disease and are in a research stage only. The United States Food and Drug Administration approved an antibody test on 2 April, but some researchers warn that such tests should not drive public health decisions unless the percentage of COVID‑19 survivors who are producing neutralizing antibodies is also known.

Virus testing statistics by country

The figures are influenced by the country's testing policy. If two countries are alike in every respect, including having the same spread of infection, and one of them has a shortage of testing capability, it may only test those showing symptoms while the other country having greater access to testing may test both those showing symptoms and others chosen at random. A country that only tests people showing symptoms will have a higher figure for “% (Percentage of positive tests)” than a country that also tests people chosen at random. If two countries are alike in every respect, including which people they test, the one that tests more people will have a higher "Positive / million people."

COVID-19 testing statistics by country

Country or region	Date	Tested	Units	Confirmed (cases)	Confirmed / tested, %	Tested / population, %	Confirmed / population, %	Ref.
Afghanistan	17 Dec 2020	154,767	samples	49,621	32.1	0.40	0.13
Albania	18 Feb 2021	428,654	samples	96,838	22.6	15.0	3.4
Algeria	2 Nov 2020	230,553	samples	58,574	25.4	0.53	0.13
Andorra	23 Feb 2022	300,307	samples	37,958	12.6	387	49.0
Angola	2 Feb 2021	399,228	samples	20,981	5.3	1.3	0.067
Antigua and Barbuda	6 Mar 2021	15,268	samples	832	5.4	15.9	0.86
Argentina	16 Apr 2022	35,716,069	samples	9,060,495	25.4	78.3	20.0
Armenia	29 May 2022	3,099,602	samples	422,963	13.6	105	14.3
Australia	9 Sep 2022	78,548,492	samples	10,112,229	12.9	313	40.3
Austria	1 Feb 2023	205,817,752	samples	5,789,991	2.8	2,312	65.0
Azerbaijan	11 May 2022	6,838,458	samples	792,638	11.6	69.1	8.0
Bahamas	28 Nov 2022	259,366	samples	37,483	14.5	67.3	9.7
Bahrain	3 Dec 2022	10,578,766	samples	696,614	6.6	674	44.4
Bangladesh	24 Jul 2021	7,417,714	samples	1,151,644	15.5	4.5	0.70
Barbados	14 Oct 2022	770,100	samples	103,014	13.4	268	35.9
Belarus	9 May 2022	13,217,569	samples	982,809	7.4	139	10.4
Belgium	24 Jan 2023	36,548,544	samples	4,691,499	12.8	317	40.7
Belize	8 Jun 2022	572,900	samples	60,694	10.6	140	14.9
Benin	4 May 2021	595,112	samples	7,884	1.3	5.1	0.067
Bhutan	28 Feb 2022	1,736,168	samples	12,702	0.73	234	1.71
Bolivia	5 Jun 2022	4,358,669	cases	910,228	20.9	38.1	8.0
Bosnia and Herzegovina	27 Sep 2022	1,872,934	samples	399,887	21.4	54.7	11.7
Botswana	11 Jan 2022	2,026,898		232,432	11.5	89.9	10.3
Brazil	19 Feb 2021	23,561,497	samples	10,081,676	42.8	11.2	4.8
Brunei	2 Aug 2021	153,804	samples	338	0.22	33.5	0.074
Bulgaria	2 Feb 2023	10,993,239	samples	1,295,524	11.8	158	18.6
Burkina Faso	4 Mar 2021	158,777	samples	12,123	7.6	0.76	0.058
Burundi	5 Jan 2021	90,019		884	0.98	0.76	0.0074
Cambodia	1 Aug 2021	1,812,706		77,914	4.3	11.2	0.48
Cameroon	18 Feb 2021	942,685	samples	32,681	3.5	3.6	0.12
Canada	26 Nov 2022	66,343,123	samples	4,423,053	6.7	175	11.7
Chad	2 Mar 2021	99,027	samples	4,020	4.1	0.72	0.029
Chile	1 Feb 2023	48,154,268	samples	5,123,007	10.6	252	26.9
China	31 Jul 2020	160,000,000	cases	87,655	0.055	11.1	0.0061
Colombia	24 Nov 2022	36,875,818	samples	6,314,769	17.1	76.4	13.1
Costa Rica	2 Nov 2021	2,575,363	samples	561,054	21.8	51.5	11.2
Croatia	2 Feb 2023	5,481,285	cases	1,267,798	23.1	134	31.1
Cuba	2 Feb 2023	14,301,394	samples	1,112,470	7.8	126	9.8
Cyprus	29 Jan 2023	27,820,163	samples	644,160	2.3	3,223	74.4
Czechia	1 Feb 2023	22,544,928	samples	4,590,529	20.4	211	42.9
Denmark	31 Jan 2023	67,682,707	samples	3,399,947	5.0	1,162	58.4
Djibouti	28 Apr 2022	305,941		15,631	5.1	33.2	1.7
Dominica	20 Jun 2022	209,803	cases	14,821	7.1	293	20.7
Dominican Republic	22 Jul 2022	3,574,665	samples	626,030	17.5	32.9	5.8
DR Congo	28 Feb 2021	124,838		25,961	20.8	0.14	0.029
Ecuador	23 Jul 2021	1,627,189	samples	480,720	29.5	9.5	2.8
Egypt	23 Jul 2021	3,137,519	samples	283,947	9.1	3.1	0.28
El Salvador	18 Mar 2022	1,847,861	samples	161,052	8.7	28.5	2.5
Equatorial Guinea	30 Jan 2023	403,773		17,113	4.2	30.8	1.3
Estonia	31 Jan 2023	3,637,908	samples	613,954	16.9	274	46.2
Eswatini	8 Dec 2021	415,110		49,253	11.9	36.5	4.3
Ethiopia	24 Jun 2021	2,981,185	samples	278,446	9.3	2.6	0.24
Faroe Islands	27 Feb 2022	774,000	samples	34,237	4.4	1,493	65.7
Fiji	2 Jan 2023	667,953	samples	68,848	10.3	74.5	7.7
Finland	14 Jan 2022	9,042,453	samples	371,135	4.1	163	6.7
France	15 May 2022	272,417,258	samples	29,183,646	10.7	417	44.7
Gabon	23 Jul 2021	958,807	samples	25,325	2.6	3.1	0.082
Gambia	15 Feb 2021	43,217	samples	4,469	10.3	2.0	0.21
Georgia	3 Nov 2021	4,888,787	samples	732,965	15.0	132	19.7
Germany	7 Jul 2021	65,247,345	samples	3,733,519	5.7	77.8	4.5
Ghana	3 Jul 2021	1,305,749	samples	96,708	7.4	4.2	0.31
Greece	18 Dec 2022	101,576,831	samples	5,548,487	5.5	943	51.5
Greenland	30 Jan 2022	164,573	samples	10,662	6.5	293	19.0
Grenada	11 May 2021	28,684		161	0.56	25.7	0.14
Guatemala	6 Jan 2023	6,800,560	samples	1,230,098	18.1	39.4	7.1
Guinea	21 Jul 2021	494,898	samples	24,878	5.0	3.8	0.19
Guinea-Bissau	7 Jul 2022	145,231		8,400	5.8	7.7	0.45
Guyana	15 Jun 2022	648,569	cases	66,129	10.2	82.5	8.4
Haiti	26 Nov 2022	223,475	cases	33,874	15.2	2.0	0.30
Honduras	26 Nov 2021	1,133,782	samples	377,859	33.3	11.8	3.9
Hungary	10 May 2022	11,394,556	samples	1,909,948	16.8	118	19.8
Iceland	9 Aug 2022	1,988,652	samples	203,162	10.2	546	55.8
India	8 Jul 2022	866,177,937	samples	43,585,554	5.0	63	31.7
Indonesia	3 Jul 2023	76,062,770	cases	6,812,127	9.0	28.2	2.5
Iran	31 May 2022	52,269,202	samples	7,232,268	13.8	62.8	8.7
Iraq	3 Aug 2022	19,090,652	samples	2,448,484	12.8	47.5	6.1
Ireland	31 Jan 2023	12,990,476	samples	1,700,817	13.1	264	34.6
Israel	17 Jan 2022	41,373,364	samples	1,792,137	4.3	451	19.5
Italy	16 Mar 2023	269,127,054	samples	25,651,205	9.5	446	42.5
Ivory Coast	3 Mar 2021	429,177	samples	33,285	7.8	1.6	0.13
Jamaica	30 Sep 2022	1,184,973	samples	151,931	12.8	43.5	5.6
Japan	1 Mar 2021	8,487,288		432,773	5.1	6.7	0.34
Jordan	6 Jun 2021	7,407,053	samples	739,847	10.0	69.5	6.9
Kazakhstan	28 May 2021	11,575,012	samples	385,144	3.3	62.1	2.1
Kenya	5 Mar 2021	1,322,806	samples	107,729	8.1	2.8	0.23
Kosovo	31 May 2021	611,357	cases	107,410	17.6	33.8	5.9
Kuwait	9 Mar 2022	7,754,247	samples	624,573	8.1	181	14.6
Kyrgyzstan	10 Feb 2021	695,415	samples	85,253	12.3	10.7	1.3
Laos	1 Mar 2021	114,030	cases	45	0.039	1.6	0.00063
Latvia	5 Sep 2021	3,630,095	samples	144,518	4.0	189	7.5
Lebanon	14 Jun 2021	4,599,186	samples	542,649	11.8	67.4	8.0
Lesotho	30 Mar 2022	431,221		32,910	7.6	21.5	1.6
Liberia	17 Jul 2021	128,246		5,396	4.2	2.5	0.11
Libya	14 Apr 2022	2,578,215	samples	501,862	19.5	37.6	7.3
Lithuania	31 Jan 2023	9,046,584	samples	1,170,108	12.9	324	41.9
Luxembourg	12 May 2022	4,248,188	samples	244,182	5.7	679	39.0
Madagascar	19 Feb 2021	119,608	cases	19,831	16.6	0.46	0.076
Malawi	29 Nov 2022	624,784	samples	88,086	14.1	3.3	0.46
Malaysia	7 Sep 2021	23,705,425	cases	1,880,734	7.9	72.3	5.7
Maldives	13 Mar 2022	2,216,560	samples	174,658	7.9	398	31.3
Mali	7 Jul 2021	322,504	samples	14,449	4.5	1.6	0.071
Malta	8 Sep 2021	1,211,456	samples	36,606	3.0	245	7.4
Mauritania	16 Apr 2021	268,093		18,103	6.8	6.1	0.41
Mauritius	22 Nov 2020	289,552	samples	494	0.17	22.9	0.039
Mexico	15 Oct 2021	10,503,678	cases	3,749,860	35.7	8.2	2.9
Moldova	20 Apr 2022	3,213,594	samples	516,864	16.1	122	19.6
Mongolia	10 Jul 2021	3,354,200	cases	136,053	4.1	100	4.1
Montenegro	10 May 2021	394,388	samples	98,449	25.0	62.5	15.6
Morocco	6 Jan 2023	14,217,563	cases	1,272,299	8.9	38.5	3.4
Mozambique	22 Jul 2021	688,570	samples	105,866	15.4	2.2	0.34
Myanmar	16 Sep 2021	4,047,680	samples	440,741	10.9	7.4	0.81
Namibia	4 Jul 2022	1,062,663	samples	166,229	15.6	38.7	6.1
Nepal	26 Jul 2022	5,804,358	samples	984,475	17.0	20.7	3.5
Netherlands	6 Jul 2021	14,526,293	cases	1,692,834	11.7	83.4	9.7
New Caledonia	3 Sep 2021	41,962	samples	136	0.32	15.7	0.050
New Zealand	29 Jan 2023	7,757,935	samples	2,136,662	27.5	156	42.9
Niger	22 Feb 2021	79,321	cases	4,740	6.0	0.35	0.021
Nigeria	28 Feb 2021	1,544,008	samples	155,657	10.1	0.75	0.076
North Korea	25 Nov 2020	16,914	cases	0	0	0.066	0
North Macedonia	1 Jul 2021	881,870	samples	155,689	17.7	42.5	7.5
Northern Cyprus	12 Jul 2022	7,096,998	samples	103,034	1.5	2,177	31.6
Norway	20 Jan 2022	9,811,888	samples	554,778	5.7	183	10.3
Oman	28 Oct 2020	509,959	samples	114,434	22.4	11.0	2.5
Pakistan	5 Mar 2021	9,173,593	samples	588,728	6.4	4.2	0.27
Palestine	5 Feb 2022	3,078,533	samples	574,105	18.6	60.9	11.4
Panama	28 Jan 2023	7,475,016	samples	1,029,701	13.8	179	24.7
Papua New Guinea	17 Feb 2021	47,490	cases	961	2.0	0.53	0.011
Paraguay	27 Mar 2022	2,609,819	samples	647,950	24.8	36.6	9.1
Peru	17 Nov 2022	36,073,768	samples	4,177,786	11.6	109.9	12.7
Philippines	7 Jan 2023	34,402,980	samples	4,073,980	11.8	34.1	4.0
Poland	27 Apr 2022	36,064,311	samples	5,993,861	16.6	94.0	15.6
Portugal	5 Jan 2022	27,515,490	samples	1,499,976	5.5	268	14.6
Qatar	11 Nov 2022	4,061,988	cases	473,440	11.7	141	16.4
Romania	29 Jan 2021	5,405,393	samples	724,250	13.4	27.9	3.7
Russia	6 Jun 2022	295,542,733	samples	18,358,459	6.2	201	12.5
Rwanda	6 Oct 2021	2,885,812	samples	98,209	3.4	22.3	0.76
Saint Kitts and Nevis	26 Aug 2021	30,231	cases	995	3.3	57.6	1.9
Saint Lucia	7 Oct 2022	212,132	samples	29,550	13.9	116.6	16.2
Saint Vincent	28 Jan 2023	113,504	cases	9,585	8.4	103.0	8.7
San Marino	29 Jan 2023	192,613	samples	23,427	12.2	563	68.4
Saudi Arabia	26 Apr 2022	41,849,069	samples	753,632	1.8	120	2.2
Senegal	12 Jul 2021	624,502	samples	46,509	7.4	3.9	0.29
Serbia	2 Feb 2023	12,185,475	cases	2,473,599	20.3	175	35.5
Singapore	3 Aug 2021	16,206,203	samples	65,315	0.40	284	1.1
Slovakia	2 Feb 2023	7,391,882	samples	1,861,034	25.2	135	34.1
Slovenia	2 Feb 2023	2,826,117	samples	1,322,282	46.8	135	63.1
South Africa	24 May 2021	11,378,282	cases	1,637,848	14.4	19.2	2.8
South Korea	1 Mar 2021	6,592,010	samples	90,029	1.4	12.7	0.17
South Sudan	26 May 2021	164,472		10,688	6.5	1.3	0.084
Spain	1 Jul 2021	54,128,524	samples	3,821,305	7.1	116	8.2
Sri Lanka	30 Mar 2021	2,384,745	samples	93,128	3.9	10.9	0.43
Sudan	7 Jan 2021	158,804	samples	23,316	14.7	0.36	0.053
Sweden	24 May 2021	9,996,795	samples	1,074,751	10.8	96.8	10.4
Switzerland	7 Nov 2022	23,283,909	samples	4,276,836	18.4	270	49.7
Taiwan	3 Feb 2023	30,275,725	samples	8,622,129	28.48	128.3	36.528
Tanzania	18 Nov 2020	3,880		509	13.1	0.0065	0.00085
Thailand	4 Mar 2021	1,579,597	cases	26,162	1.7	2.3	0.038
Togo	6 Jan 2023	807,269		39,358	4.9	9.4	0.46
Trinidad and Tobago	3 Jan 2022	512,730	cases	92,997	18.1	37.6	6.8
Tunisia	23 Aug 2021	2,893,625	samples	703,732	24.3	24.5	6.0
Turkey	2 Jul 2021	61,236,294	samples	5,435,831	8.9	73.6	6.5
Uganda	11 Feb 2021	852,444	samples	39,979	4.7	1.9	0.087
Ukraine	24 Nov 2021	15,648,456	samples	3,367,461	21.5	37.2	8.0
United Arab Emirates	1 Feb 2023	198,685,717	samples	1,049,537	0.53	2,070	10.9
United Kingdom	19 May 2022	522,526,476	samples	22,232,377	4.3	774	32.9
United States	29 Jul 2022	929,349,291	samples	90,749,469	9.8	281	27.4
Uruguay	16 Apr 2022	6,089,116	samples	895,592	14.7	175	25.8
Uzbekistan	7 Sep 2020	2,630,000	samples	43,975	1.7	7.7	0.13
Venezuela	30 Mar 2021	3,179,074	samples	159,149	5.0	11.0	0.55
Vietnam	28 Aug 2022	45,772,571	samples	11,403,302	24.9	46.4	11.6
Zambia	10 Mar 2022	3,301,860	samples	314,850	9.5	19.0	1.8
Zimbabwe	15 Oct 2022	2,529,087	samples	257,893	10.2	17.0	1.7

References

 This article incorporates public domain material from Symptom-Based Strategy to Discontinue Isolation for Persons with COVID-19. Centers for Disease Control and Prevention. Retrieved 5 May 2020.

External links

• Data on COVID-19 testing at Our World in Data (31 March 2020)
• COVID-19 Testing (at least) – now Free for all? (CDC; US Congress; CSPAN video/6:00; March 12, 2020)
• Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR; NCBI-PMC, DOI (23 January 2020)
• "EUA Authorized Serology Test Performance". U.S. Food and Drug Administration (FDA).