COVID-19 testing

The US CDC's COVID-19 laboratory test kit

COVID-19 testing involves analyzing samples that indicate the present or past presence of SARS-CoV-2. The two main branches detect either the presence of the virus or of antibodies produced in response to infection. Tests for viral presence are used to diagnose current illness and to allow public health authorities to identify and contain outbreaks as quickly as possible. Antibody tests instead show how many people have had the disease, including those whose symptoms were minor or who were asymptomatic, but may not find antibodies in someone with a current COVID-19 infection since antibodies may not show up for weeks. An accurate disease mortality rate can be determined from the results of this test. Another use of antibody tests is to identify individuals whom the antibodies have rendered immune to the disease, together with the level of herd immunity in the population, although research has yet to confirm in the case of COVID-19 that a positive test confers such immunity.

Individual jurisdictions have adopted a broad range of testing protocols. They vary in choosing whom to test, how often to test, analysis protocols, sample collection and the uses of test results. This variation has likely significantly impacted countries' reported statistics, including case fatality rates and the age distribution of cases, due to sampling bias. Testing is often performed in automated, high-throughput centralized medical laboratories by medical laboratory scientists. Alternatively, point-of-care testing can be done in physician's offices, workplaces or transit hubs.

Test methods

Explanation of the underlying pathophysiology pertaining to diagnosis of COVID-19

The two broad categories of test are: a viral test for a current infection, or an antibody test for the past presence of the virus. Other techniques include a CT scan, checking for elevated body temperature or checking for low blood oxygen level.

Current infection

Polymerase chain reaction

Polymerase chain reaction (PCR) is a process that amplifies (replicates) a small, well-defined segment of DNA many hundreds of thousands of times, creating enough of it for analysis. Test samples are treated with certain chemicals that allow RNA to be extracted.

Reverse transcription polymerase chain reaction (RT-PCR) is a technique that first uses reverse transcription to convert RNA into DNA and then uses PCR to amplify that DNA, creating enough to be analyzed. RT-PCR is used for SARS-CoV-2, which contains only RNA.

Real-time PCR (qPCR) provides advantages including automation, higher-throughput and more reliable instrumentation. It has become the preferred method.

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 are used as abbreviations. The Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines propose the term RT-qPCR, but not all authors adhere to this.

The test can be done on samples obtained by various methods, including a nasopharyngeal swab, sputum (coughed up material), throat swabs, deep airway material via suction catheter or saliva. Drosten et al. remarked that for 2003 SARS, "from a diagnostic point of view, it is important to note that nasal and throat swabs seem less suitable for diagnosis, since these materials contain considerably less viral RNA than sputum, and the virus may escape detection if only these materials are tested."

The RT-PCR process generally requires a few hours.

The likelihood of detecting the virus depends on sample collection method how much time has passed since infection. According to Drosten tests performed with throat swabs are reliable only in the first week. Thereafter the virus may abandon the throat and multiply in the lungs. In the second week, sputum or deep airways collection is preferred.

Collecting saliva may be as effective as nasal and throat swabs, although this is not certain. Sampling saliva may reduce the risk for health care professionals by eliminating close physical interaction. It is also more comfortable for the patient. Quarantined people can collect their own samples. Saliva test's diagnostic value depends on how specimens are collected (from deep throat, from oral cavity, or from salivary glands). A Yale University School of Public Health study found that saliva yielded greater sensitivity and consistency throughout the course of infection when compared with swab samples.

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

Isothermal amplification assays

Isothermal nucleic acid amplification tests also amplify the virus's genome. They are faster than PCR because they don't involve repeated heating and cooling cycles. These tests typically detect DNA using fluorescent tags, which are read out with specialized machines. CRISPR gene editing technology was modified to perform the detection: if the CRISPR enzyme attaches to the sequence, it colors a paper strip. The researchers expect the resulting test to be cheap and easy to use in point-of-care settings. The test amplifies RNA directly, without the RNA-to-DNA conversion step of RT-PCR.

Antigen

An antigen is the part of a pathogen that elicits an immune response. Antigen tests look for antigen proteins from the viral surface. In the case of a coronavirus, these are usually proteins from the surface spikes. One of the challenges is to find a target unique to SARS-CoV-2.

Antigen tests may be one way to scale up testing to much greater levels. Isothermal nucleic acid amplification tests can process only one sample at a time per machine. RT-PCR tests are accurate but require 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 17 April 2020. "But there might be with the antigen test."

A nasopharyngeal swab is exposed to paper strips containing artificial antibodies designed to bind to coronavirus antigens. Antigens bind to the strips and give a visual readout. The process takes less than 30 minutes, can deliver results at point of care, and does not require expensive equipment or extensive training.

Swabs of respiratory viruses often lack enough antigen material to be detectable. This is especially true for asymptomatic patients who have little if any nasal discharge. Viral proteins are not amplified in an antigen test. According to the 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. According to the FDA, positive results from antigen tests are highly accurate, but there is a higher chance of false negatives, so negative results do not rule out infection. Therefore, negative results from an antigen test may need to be confirmed with a PCR test.

Imaging

Typical visible 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. Chest CT scans and chest x-rays are not recommended for diagnosing COVID-19. Radiologic findings in COVID-19 lack specificity.

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 test blood and can identify once-infected people who have recovered.

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 several days after initial infection, although levels over the course of infection are not well characterized. SARS-CoV-2 IgG antibodies generally become detectable 10–14 days after infection, sometimes earlier, and normally peak around 28 days after infection onset. Antibodies are too slow to serve as acute infection markers. Since they may persist in the bloodstream for many years they are ideal for detecting past infections.

Antibody tests can be used to estimate the once-infected percentage of a population who are therefore presumably immune. However, SARS-CoV-2 antibodies' potency and protective period are unclear.

Types of serology tests

Rapid diagnostic test (RDT)

RDTs typically use a small, portable, positive/negative lateral flow assay that can be executed at point of care. RDTs may process blood samples, saliva samples, or nasal swab fluids. RDTs produce colored lines to indicate positive or negative results.

Enzyme-linked immunosorbent assay (ELISA)

ELISAs can be qualitative or quantitative and generally requires a lab. These tests usually use whole blood, plasma, or serum samples. A plate is coated with a viral protein, such as SARS-CoV-2 spike protein. Samples are incubated with the protein, allowing any antibodies to bind to the protein. The antibody-protein complex can then be detected with another wash of antibodies that produce a color/fluorescent readout.

Neutralization assay

Neutralization assays lab test observes whether sample antibodies prevent viral infection in test cells. These tests also sample blood, plasma or serum. The test cultures cells that allow viral reproduction (e.g., VeroE6 cells). By varying antibody concentrations, researchers can visualize and quantify how many test antibodies block virus replication.

Chemiluminescent immunoassay

Chemiluminescent immunoassays are quantitative lab tests. These tests sample blood, plasma, or serum. Samples are mixed with a known viral protein, buffer reagents and specific, enzyme-labeled antibodies. The result is luminescent. A chemiluminescent microparticle immunoassay uses magnetic, protein-coated microparticles. Antibodies react to the viral protein, forming a complex. Secondary enzyme-labeled antibodies are added and bind to these complexes. The resulting chemical reaction produces light. The radiance is used to calculate the number of antibodies. This test can identify multiple types of antibodies, including IgG, IgM, and IgA.

Neutralizing vs binding antibodies

Most if not all large scale COVID-19 antibody testing is for detection of binding antibodies only and does not measure neutralizing antibodies (NAb). A NAb is an antibody that defends a cell from a pathogen or infectious particle by neutralizing its biological effects. Neutralization renders the particle no longer infectious or pathogenic. A binding antibody binds 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 return a positive result if they find only binding antibodies, these tests cannot indicate that the subject has generated protective NAbs, which protect 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 established for COVID-19. A study of 175 recovered patients in China who experienced mild symptoms reported that 10 individuals had no detectable NAbs at the time of discharge, or thereafter. How these patients recovered without the help of NAbs and whether they were at risk of re-infection was not addressed. An additional source of uncertainty is that even if NAbs are present, viruses such as HIV can evade NAb responses.

It is presumed that a post-infection patient has a low chance of a second infection, but the duration of protective immunity is not established. Studies have indicated that NAbs to the original SARS virus (the predecessor to the current SARS-CoV-2) can remain active 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 reduce the severity of a reinfection.

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

Infectivity

Infectivity is indicated by the basic reproduction number (R₀, pronounced "R naught") of the disease. At the highest level, the R₀ of SARS-CoV-2 is estimated to be from 2.2 to 2.5, meaning that in a population where all individuals are susceptible to infection, each infected person is expected to infect 2.2 to 2.5 others. However this can vary according factors such as geography, population demographics, density. In New York state R₀ was estimated to be 3.4 to 3.8. On average, an infected person begins showing symptoms five days after infection (the "incubation period") and can infect others two to three days before that. One study reported that 44% of viral transmissions occur within this period. According to CDC, a significant number of infected people who never show symptoms are nevertheless contagious.

After infection, patients remain infectious for an uncertain interval, but in vitro studies have not found replication-competent virus after 9 days.

1. Viral burden measured in upper respiratory specimens declines after onset.
2. Replication-competent virus has yet to be cultured more than nine days after onset of illness. The statistically estimated likelihood of recovering replication-competent virus approaches zero by 10 days.
3. As time passes post-infection 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 low but detectable (i.e., Ct values higher than 33-35).
5. Following recovery, many patients no longer have detectable viral RNA in upper respiratory specimens. Among those who do, RNA concentrations three days following recovery are generally below the range in which replication-competent virus has been reliably isolated.
6. No clear correlation has been described between length of illness and duration of post-recovery shedding of 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.

Patterns and duration of illness and infectivity have not been fully described. However, available data indicate that SARS-CoV-2 RNA shedding in upper respiratory specimens declines after symptom onset. At 10 days recovery of replication-competent virus in viral culture (as a proxy of the presence of infectious virus) approaches zero. Although patients may produce PCR-positive specimens for up to six weeks, it remains unknown whether these samples hold infectious virus. After clinical recovery, many patients do not continue to shed. Among recovered patients with detectable RNA in upper respiratory specimens, concentrations after three days are generally below levels where virus has been reliably cultured. These data were generated from adults across a variety of age groups and with varying severity of illness. Data from children and infants were not available.

Minimum testing necessary

Successful reopening requires effective containment of the pandemic. Infected people must be identified and isolated before they infect others. Because of presympomatic transmission, containing the disease requires testing and isolation before symptoms.

According to Harvard's Global Health Institute, the US's required testing level is more than 900,000 per day. Other estimates range up to 23 million tests per day. Testing rates have steadily increased, averaging 468,000 per day for the week ending 14 June 2020.

WHO recommends increasing testing until fewer than 10% are positive in any given jurisdiction. As of 14 June 2020, the percentage testing positive in the US as a whole had declined to below 5%.

Economist Paul Romer reported that the US has the technical capacity to scale up to 20 million tests per day, which is his estimate of the scale needed to fully remobilize the economy. The Edmond J. Safra Center for Ethics estimated on 4 April that this capacity could be available by late July.

Romer points to single-molecule real-time sequencing equipment from Pacific Biosciences, which is in use in 20 US laboratories. and to the Ion Torrent Next-Generation Sequencing equipment from ThermoFisher Scientific, which is in use in 16. According to Romer, "Recent research papers suggest that any one of these has the potential to scale up to millions of tests per day." He added that this plan would require removing FDA regulatory hurdles. Romer estimated that Congress would need to appropriate $100 billion to fund the process.

Romer also claimed that even a relatively inaccurate test, if administered frequently enough, could accomplish the goal. He ran simulations in which 7% of the population is tested every day with a test with a 20% false negative rate and a 1% false positive rate. The average person would be tested roughly every two weeks and those who tested positive would go into quarantine. Romer concluded that the fraction of the population that is infected at any given time (known as the attack rate) peaks early, reaching roughly 8% of the population in about thirty days and then gradually declines, in most runs reaching zero at 500 days, with the cumulative fraction of the population that is ultimately infected kept below 20%. Romer adds that these results are indicative, not predictive about the true spread of the virus.

History

Timeline of total number of tests in different countries

Scientists from China first released information on the viral genome on 11 January 2020. That day the Malaysian Institute for Medical Research (IMR) produced the "primers and probes" specific to a SARS-CoV-2 RT-PCR test. The IMR's materials were used to diagnose Malaysia's first patient on 24 January. In January BGI Group was one of the first companies to receive emergency use approval from China's National Medical Products Administration for a nucleic acid test.

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.

The German nucleic acid testing protocol was published on 17 January 2020. Another early PCR test was developed by Charité university hospital 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).

In the US, the CDC developed its SARS-CoV-2 Real Time PCR Diagnostic Panel. The US protocol developed by the CDC became available on 28 January. One of three tests in early versions of the kits caused inconclusive results due to faulty reagents. CDC refused to let other labs process tests; allowing an average of fewer than 100 samples a day to be processed throughout February. Tests using two components were not determined to be reliable until 28 February, 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.

South Korean company Kogenebiotech's clinical grade, nucleic acid test (PowerChek Coronavirus) was approved by Korea Centers for Disease Control and Prevention (KCDC) on 4 February 2020.

In Wuhan BGI opened a makeshift 2000-sq-meter emergency detection laboratory named "Huo-Yan" (Chinese: 火眼, "Fire Eye") on 5 February 2020. It can process more than 10,000 samples a day. Construction was overseen by BGI-founder Wang Jian and required 5 days. The Wuhan Laboratory was followed by Huo-Yan labs in Shenzhen, Tianjin, Beijing, and Shanghai, in a total of 12 cities across China. By 4 March the daily throughput totals were 50,000 tests per day.

March

On 16 March WHO called for ramping up the testing programmes as the best way to slow the spread.

In March, shortages and insufficient amounts of reagent became a bottleneck for mass testing in the EU and UK and the US.

On 12 March 2020, Mayo Clinic announced a nucleic acid test.

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

US commercial labs began testing in early March 2020. As of 5 March LabCorp announced nationwide availability of COVID‑19 testing based on RT-PCR. Quest Diagnostics made nationwide testing available as of 9 March. US testing demand grew rapidly, causing backlogs of hundreds of thousands of tests at private US labs. Supplies of swabs and chemical reagents became strained. On 25 May 2020, the US required each state to take responsibility for meeting its testing needs. In March, the FDA issued EUAs for nucleic acid tests to Hologic (3/16), Abbott Laboratories (3/18), Thermo Fisher Scientific (3/19) Cepheid (3/21) and LabCorp (4/30).

On 27 March 2020, the FDA issued an Emergency Use Authorization for a test by Abbott Laboratories' ID Now assay.

By 31 March United Arab Emirates was testing more of its population per head than any other country. UAE implemented a combination of drive-through capability, and mass-throughput laboratory from Group 42 and BGI. The lab conduced tens of thousands RT-PCR tests per day and was the first to be operational at this scale outside of China.

Several European countries initially conducted more tests than the US. By 19 March drive-in tests were offered in several large cities. As of 26 March, Health minister Jens Spahn estimated that Germany was conducting 200,000 tests per week. As of the end of March at least 483,295 samples were tested and 33,491 (6.9%) had tested positive.

A test that 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.

April

The FDA approved an antibody test on 2 April,

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".

May

In May antibody tests were conducted on 5,603 major league baseball employees and 0.7% tested positive, showing they had been infected in the past. 70% of those who tested positive had had no symptoms. The US was conducting an average of 2.5 million tests per week for the week ending 17 May. This grew to 3.2 million by 14 June.

On 8 May, the FDA granted its first EUA for antigen test: "Sofia 2 SARS Antigen FIA" by Quidel Corp.

On 3 May, Roche received an EUA for a selective ELISA serology test.

On 21 May, researchers at Ben-Gurion University in Israel reported a one-minute coronavirus test with 90% accuracy, based on the "change in the resonance in the THz spectral range" shown by the coronavirus through THz spectroscopy.

June

In early June, researchers announced a nucleic acid diagnostic test using reverse transcription-loop-mediated isothermal amplification (RT-LAMP), an existing technology used in pathogenic microorganism identification, genetically modified ingredients, tumor detection, and embryo sex identification. The test identified virus in samples of serum, urine, saliva, oropharyngeal swabs and nasopharyngeal swabs. Once commercialized the test has the potential to provide rapid (30-45 minute) diagnosis at point of care. The test was 100% selective and highly sensitive, detecting virus at a concentration of .06 fg/ml.

Capacity

Germany has a large medical diagnostics industry, with more than a hundred testing labs that provided the technology and infrastructure to enable rapid increases in testing. Costs are borne by insurance when the test is ordered by a physician. According to the president of the Robert Koch Institute, Germany had an overall capacity for 160,000 tests per week.

South Korea's broad testing approach helped reduce spread. Testing capacity, largely in private sector labs, was built up over several years by the South Korean government.

By the start of April, the United Kingdom was delivering around 10,000 swab tests per day. The British NHS announced that it was piloting a scheme to test suspected cases at home, to remove the risk of one patient infecting others at a hospital or disinfecting an ambulance used to transport a patient.

Services

A sample collection kiosk for COVID-19 testing in India

Drive-through testing

In drive-through testing, a healthcare professional takes a sample using appropriate precautions, such as wearing PPE. Drive-through centers helped South Korea accelerate its testing program.

Home collection

In Hong Kong test can stay home, while "[the] emergency department will give a specimen tube to the patient". They spit into it, return it and later get the result.

Pooled testing

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 was found to be positive. Pool testing was then adopted in Israel, Germany, South Korea, Nebraska, and the Indian states of Uttar Pradesh, West Bengal, Punjab, Chhattisgarh and Maharashtra.

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

Number of tests done per day in the US.
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.

Available tests

A temporary drive-in testing site for COVID-19 set up with tents in a parking lot

Countries around the world developed tests independently and in partnership with others.

Nucleic acid tests

Tests developed in China, France, Germany, Hong Kong, Japan, the United Kingdom, and the US targeted different parts of the viral genome. WHO adopted the German system for manufacturing kits sent to low-income countries without the resources to develop their own.

PowerChek Coronavirus looks for the "E" gene shared by all beta coronaviruses, and the RdRp gene specific to SARS-CoV-2.

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

Abbott Laboratories' ID Now nucleic acid test uses isothermal amplification technology. 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 is widely deployed in the US. The device can be used in laboratories or in point of care settings, and provides results in 13 minutes or less. Initially Abbott offered 50,000 test kits per day.

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.

Primerdesign offers its Genesig Real-Time PCR Coronavirus (COVID‑19). Cobas SARS-CoV-2 Qualitative assay runs on the Cobas® 6800/8800 Systems by Roche Molecular Systems. They are offered by the United Nations and other procurement agencies.

Antigen tests

Quidel's "Sofia 2 SARS Antigen FIA" is a lateral flow test that uses monoclonal antibodies to detect the virus's nucleocapsid (N) protein. The result is read out by the company's Sofia 2 device using immunofluorescence. The test is simpler and cheaper but less accurate than nucleic acid tests. It can be deployed in laboratories or at point of care and gives results in 15 minutes. A false negative result occurs if the sample's antigen level is below the test's detection limit test and should be confirmed with a nucleic acid test.

Serology (antibody) tests

Antibodies are usually detectable 14 days after the onset of the infection. Multiple survey their populations using these tests.

Fifteen antibody tests have EUA approvals for diagnosis. Other tests have been approved in other countries. The test requires a blood draw.

Private US labs including Quest Diagnostics and LabCorp offer antibody testing to the general public.

Antibody tests are also available in various European countries. The testing capacity is several hundred samples within hours.

Roche offers a selective ELISA serology test.

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

Accuracy

Accuracy is measured in terms of specificity and selectivity. Test errors can be false positives (the test is positive, but the virus is not present) or false negatives, (the test is negative, but the virus is present).

Sensitivity and specificity

Main article: Sensitivity and specificity

Sensitivity indicates whether the test accurately identifies whether the virus is present. A 90% sensitive test will correctly identify 90% of infections, leaving 10% with a false negative result. Each test requires a minimum level of viral load in order to produce a positive result. Even apparently high sensitivity rates can produce high rates of false negatives in populations with low incidence rates.

Specificity indicates how well-targeted the test is to the virus in question. Highly specific tests pick up only the virus in question. Non-selective tests pick up other viruses as well. A 90% specific test will correctly identify 90% of those who are uninfected, leaving 10% with a false positive result.

Low-specificity tests have a low positive predictive value (PPV) when prevalence is low. For example, suppose incidence is 5%. Testing 100 people at random using a test that has a specificity of 95%. In that case on average 5 people who are actually negative would incorrectly test positive. Since 5% of the people actually are positive, another five would also test positive correctly, totaling 10 positives. Thus, the PPV is 50%, an outcome no different from a coin toss. In this situation retesting those with a positive result increases the PPV to 94.5%, meaning that only 4.5% of the second tests would return the incorrect result.

Causes of test error

Improper sample collection, exemplified by failure to acquire enough sample and failure to insert a swab deep into the nose, is one cause of low clinical sensitivity.

The time course of infection also affects accuracy. Samples may be collected before the virus has had a chance to establish itself or after the body has stopped its progress and begun to eliminate it.

RNA breakdown due to improper storage for too long time can also lead to wrong results as viral particles disintegrate.

Test makers typically report the accuracy levels of their tests when seeking approval from authorities. In some jurisdictions, these results are cross-validated by additional assessments. Post-approval assessments have been published in many contexts.

PCR-based test

Detection of SARS-CoV-2 by nasal swab over six weeks in patients who experienced mild to moderate illness

RT-PCR is considered the most accurate diagnostic test. It has high sensitivity and specificity in a laboratory setting: in one study sensitivity dropped to 66-88% clinically.

In one study sensitivity was highest at week one (100%), followed by 89.3%, 66.1%, 32.1%, 5.4% and zero by week six.

Early in March 2020, China reported accuracy problems with its tests. A study examined 1070 samples from 205 Wuhan patients and reported varied sensitivity according to the methods and location of sample collection. Samples from bronchoalveolar lavage fluid specimens returned the highest sensitivity. The authors argued that CT scan showed even higher sensitivity.

Spain purchased test kits from Chinese firm Shenzhen Bioeasy Biotechnology Co Ltd, but found that results were unacceptable. The maker explained that the incorrect results may stem from failure to collect samples or use the kits correctly. The Spanish ministry switched to another vendor, Shenzhen Bioeasy.

The location of sample collection impact on sensitivity for COVID-19 in 205 Wuhan patients

Samples from ...	Positive rate
Bronchoalveolar lavage fluid specimens	93% (n=14)
Sputum	72% (n=75)
Nasal swabs	63% (n=5)
Fibrobronchoscope brush biopsy	46% (6/13)
Pharyngeal swabs	32% (n=126)
Feces	29% (n=44)
Blood	1% (n=3)

A Dutch CDC-led laboratory investigation compared 7 PCR kits. Test kits made by BGI, R-Biopharm AG, BGI, KH Medical and Seegene showed high sensitivity. High sensitivity kits are recommended to diagnose people with low viral loads, while others are adequate when used for diagnostics of symptomatic patients.

Isothermal nucleic amplification test

One study reported that the ID Now COVID-19 test showed sensitivity of only 85.2%. Abbott responded that the issue could have been caused by storing the samples instead of inserting them immediately into the testing machine. Another study rejected the test in their clinical setting because of its low sensitivity. The FDA announced on 14 May a review of 15 adverse event reports about the Abbott ID Now device for low sensitivity.

Antibody test

The prevalence of SARS-CoV-2 antibody positive individuals is not known. Antibody survey results have found from 2% to 30% positive. On preliminary data, WHO concluded that 2% to 3% of the world population has developed antibodies.

Nearly two million antibody tests imported into Australia and costing $20 million were declared unusable. 80% of test kits that Czechia purchased from China gave wrong results. Slovakia purchased 1.2 million antibody-based test kits from China that were found to be inaccurate. China accused Czechia and Slovakia of incorrect use of those tests. Ateş Kara of the Turkish Health Ministry said the test kits Turkey purchased from China had a "high error rate". The UK purchased 3.5 million antibody test kits from China, but in early April 2020 announced these were not usable. On 21 April 2020, the Indian Council of Medical Research (ICMR) advised Indian states to stop using 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.

Confirmatory testing

The WHO recommends 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 sixteen reference laboratories, seven are in Asia, five in Europe, two in Africa, one in North America and one in Australia.

National responses

Italy

Researchers tested the entire population of Vò, the site of Italy's first COVID‑19 death. They tested about 3,400 people twice, at an interval of ten days. About half the people testing positive had no symptoms. All discovered cases were quarantined. Along with restricting travel to the commune, new infections were completely eliminated.

Japan

Unlike other Asian countries, Japan did not have a pandemic of SARS or MERS, so the country's PCR testing system was not well equipped. Japan preferentially tested patients with severe illness and those who were in close contact with infected people at the beginning. The Novel Coronavirus Expert Meeting chose the cluster measures to attack clusters of infected people. At the same time, the Expert Meeting analyzed the outbreak from Wuhan and discovered the conditions leading to clusters, closed spaces, crowded spaces and close-contact), and asked people to avoid such settings. In January, contact tracers took action shortly after the first infection was found. Only administrative tests were carried out at first, but insurance began covering PCR tests on March 6. Private companies began to test, and the test system gradually expanded. On April 3, those with positive tests were legally permitted to recuperate at home or in a hotel if they had asymptomatic or mild illness, which solved the shortage of hospital beds. The first wave (from China) was contained, but the second wave (caused by returnees from Europe and the US) in mid-March led to spreading infection in April. On April 7, Japan declared a state of emergency, (less strict than a lockdown, because it did not block cities or restrict outing). On May 13, antigen test kits became covered by insurance, and was combined with a PCR test for diagnosis. The number of PCR tests per capita is far smaller than in some other countries even though the positive test rate is lower. No excess mortality occurred until March. The Expert Meeting stated, "The Japanese health care system originally carries out pneumonia surveillance, allowing it to detect most of the severely ill patients who develop pneumonia. There are a large number of CT scanners in Japan and they have spread to small hospitals all over the country, so pneumonia patients are rarely missed. In that sense, it meets the same standards as other countries that mainly carry out PCR tests." The Expert Meeting recommended using CT scans data and doctor's findings to detect coronavirus. In Diamond Princess, many cases people who initially tested negative later tested positive. Half of coronavirus-positives there who remained mild or asymptomatic had pneumonia findings on CT scans and their CT image showed a frosted glass shadow that is characteristic of the COVID-19.

Russia

On 27 April, Russia tested 3 million people and had 183,000 people. 87,147 people tested positive. The total confirmed deaths reached 794. On 28 April Anna Popova, head of Federal Service for Surveillance in Healthcare (Roszdravnadzor) stated that 506 laboratories were testing; that 45% of those who tested positive had no symptoms, 5% of patients had a severe form; 40% of infections were from family members. The speed of people reporting illness improved from six days to one day after symptoms appeared. Antibody testing was carried out on 3,200 Moscow doctors. 20% had immunity.

Singapore

With contact tracing, inbound travel restrictions, testing, and quarantining, Singapore arrested the spread, without complete lockdown. Many events were cancelled. Singapore advised residents to stay at home on 28 March, but schools reopened on time after holiday break on 23 March. Schools moved to "full home-based learning" on 8 April.

South Korea

South Korea used PCR tests to prevent the spread of infection after the first case was confirmed on January 19. The government exploited the resident registration number (RRN) system. Authorities mobilized young men who were eligible for military service as social service agents, security and public health doctors. Public health doctors were mainly dispatched to public health centers and life treatment centers where mildly ill patients were accommodated, performed PCR tests and managed mild patients. Social service agents worked in pharmacies to fill staff shortages. Soldiers and veterans were mobilized for packaging and shipping at mask factories. The government used the RRN and a Drug Utilization Review (DUR) system to restrict individual mask purchases. Korea's 10k PCR tests per million residents was the world's highest as of April 13 rising to 20k by mid-June. Twenty-seven Korean companies exported test kits worth $48.6 million in March, and were asked to provde test kits or humanitarian assistance by more than 120 countries. Korean authorities set up a treatment center to isolate and manage patients with asymptomatic and minor illnesses in one facility in order to vacate hospital beds for the more severely ill.

The first outbreak appeared at the church of the "Shincheonji Church of Jesus" on February 18 in the Daegu region. Authorities raised the crisis alert to the highest level of "seriousness" on February 23, recommending self-control of events in confined indoor spaces and crowded areas.

Centers were sited mainly at national facilities and corporate training centers. The failure of Korea's MERS quarantine in May 2015 left the Korean government more sensitive to COVID-19. Then President Park Geun-hye allowed Korean CDC-approved private sector testing for infectious diseases in 2016. Korea already had a system for isolating, testing and treating infectious disease patients separately from other patients. Patients with respiratory illness but no epidemiological relevance were treated at the National Hospital, and those with epidemiological relevance were treated at selected clinics.

Korea established a large scale drive-through/walk-through" test testing program. However, the most common method is “mobile examination”. In Daegu City. 54% of samples were collected by March 23 in a patient's home or hospital. Collecting samples door-to-door of avoided the risk of travel by possibly infected patients, but required additional staff. Korea solved the problem by drafting more than 2,700 public insurance doctors.

The government disclosed personal information to the public via KCDC without patient consent. The authorities used digital surveillance to trace possible spread. The RRN is linked to information such as credit card usage history, smartphone GPS information, visa travel history, health insurance and workplace. Authorities fused that information with video from surveillance cameras. The behavior history of new infected persons was disclosed on each municipality's website, including demographics such as sex, age group, name of place of residence, facility used and workplace and personal relationships. The guidelines were later revised to reduce disclosure after criticism over privacy violations. A smartphone app receives an alert when an infectious patient appears in the neighborhood. When individuals violates quarantine, the app sends an alert. Violators are subject to fine and imprisonment won and may be required to wear a wristband. Critics likened the practice to the ankle monitor worn by sex offenders.

Taiwan

Taiwan's early response reduced the number of cases and deaths to low levels. Since late March, the number of new infections per day remained low. Taiwan implemented most of its virus containment policies in January. The Taiwan government noticed the events in Wuhan before any other country, and alerted WHO on December 31, 2019 of infections with SARS characteristics. Travelers from Wuhan were quarantined.

Health insurance IDs and national identification card numbers were used to trace contacts. The government eliminated an original mask shortage by purchasing all masks manufactured in Taiwan and then selling them. Audrey Tan, a white hat hacker, created an app that allowed citizens to know the number of masks. The authorities invested in mask factories across Taiwan to build more production lines and mobilize military personnel to address labor shortages.

Taiwan did not city blockade or school closure, relying on measures such as requiring public transport users to wear masks and fining offenders. Taiwan isolated infected people and returnees from abroad for 14 days and fined up to 1 million Taiwan dollars for violating quarantine. Detainees are remotely monitored using GPS on smartphones.

Taiwan has a universal health insurance system, and everyone has an insurance card with an IC chip. The personal number is common to official documents, making it easy to track overseas travel and treatment.

Strict measures such as restrictions on the departure of medical personnel to maintain the domestic medical system and surveillance of infected persons in quarantine were sometimes criticized for overly restricting rights and for lacking legal grounds.

About 1 million Taiwanese live in China, raising the risk of transmission to Taiwan.

United States

New York State

New York State's control measures consisted of three major pillars: (1) increasing the number of PCR tests, (2/) stay-at-home measures, (3) strengthening the healthcare system. On February 29, before its first case, NY allowed testing at the Wordsworth Center by having the CDC approve tests at state laboratories and by having the FDA approve a test kit. As of March 13 NY was testing more than 1,000 daily tests, growing to 10,000/day on March 19. In April, the number exceeded 20,000. Many people queued at hospitals to get tested. On March 21 New York City health officials directed medical providers to stop testing patients, except for those entering the hospital, for lack of PPE. On March 24, a NYC medical worker succumbed. Colleagues posted a picture of themselves wearing garbage bags instead of medical scrubs on Facebook, claiming the hospital lacked PPE.

USS Theodore Roosevelt

Main article: COVID-19 pandemic on USS Theodore Roosevelt

After 94% of the 4,800 aircraft carrier crew had been tested, roughly 60 percent of the 600-plus sailors who tested positive were asymptomatic. Sailors who test positive had to spend at least two weeks in isolation and then test negative twice, with the tests separated by at least a day. Five sailors who went through this process and had been admitted back onto the ship subsequently developed flu-like symptoms and again tested positive.

Iceland

Iceland managed the pandemic with aggressive contact tracing, inbound travel restrictions, testing, and quarantining, but with less aggressive lock-downs.

Statistics by country

Testing strategies vary by country and over time, with some countries testing very widely, while others have at times focused narrowly on only testing the seriously ill. 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 test only those showing symptoms while the other country having greater access to testing may test more widely. The country that tests only people showing symptoms will have a higher figure for "% (Confirmed cases as percentage of tested samples or tested cases)" than the country that also tests others. If two countries are alike in every respect, including which people they test, the one that tests more people will have a higher "Confirmed / 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). 4 June 2020.
• "Global Progress on COVID-19 Serology-Based Testing". Johns Hopkins Center for Health Security. 5 June 2020. Retrieved 9 June 2020.
• "EUA Authorized Serology Test Performance". FDA. 22 May 2020. Retrieved 29 May 2020.
• Health, Center for Devices and Radiological (15 June 2020). "EUA Authorized Serology Test Performance". FDA.