Testing Hub

Testing FAQ

These FAQs provide answers to some of the most frequently asked questions on COVID-19


Who started the Testing Insights Initiative and why?

The Testing Initiative is the result of support from Bloomberg Philanthropies and the Stavros Niarchos Foundation as long-term philanthropic partners of the university, in addition to outreach and encouragement from Senator Mark Warner. Policy makers from across the country, including at the federal level have sought a centralized hub for information and data about testing as they evaluate plans to re-open economies and craft policy responses to counter the spread of the disease. The new Testing Insights Initiative will provide such a resource and help guide leaders as they consider how and when to re-open.

The COVID-19 Testing Insights Initiative reflects an interdisciplinary collaboration between several groups at Johns Hopkins University: The Bloomberg School of Public Health, Applied Physics Laboratory, Center for Health Security, Center for Systems Science and Engineering (CSSE) in the Whiting School of Engineering, and the Centers for Civic Impact, which is supported in part by Bloomberg Philanthropies. Data and technical support is provided by the Atlantic’s COVID Tracking Project, ESRI and the JHU Sheridan Libraries.

How is COVID-19 diagnosed?

In the United States, diagnostic testing for COVID-19 involves testing for the presence of the virus in specimens obtained from patients. Almost all diagnostic testing for COVID-19 is done using PCR-based methods, which look for the genetic material of the SARS-CoV-2 virus, which causes COVID-19. These methods can only diagnose someone with COVID-19 if they are actively infected. Currently, most diagnostic tests for COVID-19 test nasopharyngeal or oropharyngeal specimens (nose or throat swabs). Recently, the FDA granted Emergency Use Authorization to a laboratory to test patients’ saliva.

What are limitations to COVID-19 diagnostic tests?

With any diagnostic test, there is the potential for false negatives or false positives. For existing COVID-19 tests in the U.S., there have been reports of false negative tests in some patients. False negative tests can occur if a specimen was not properly obtained or if a patient was tested too early or too late in their infection. Laboratory error is also a possible cause of false negative test results. Conversely, false positive reports are less common.

Who should be tested for COVID-19?

Individuals who have symptoms of COVID-19 should be tested for the SARS-CoV-2 virus so that they will know to isolate themselves from others so as not to spread the disease. In certain cases, such as outbreak investigation, testing of people without symptoms is also indicated. However, current limitations in testing capacity have restricted who may be tested for COVID-19. Recommendations regarding who should and can be tested differ by state. Some states that have experienced large numbers of COVID-19 cases have requested that individuals who are experiencing symptoms of COVID-19 assume that they are positive and avoid health facilities unless they experience severe symptoms.

What are serology tests and how are they used?

Serology tests are blood-based tests that can be used to identify whether people have been exposed to a particular pathogen by looking at their antibodies, or specific proteins produced by the body in response to an infection. Serology tests can be helpful in determining whether someone was infected in the past with the coronavirus, whether or not they ever developed symptoms of the disease.

In contrast, the PCR tests currently being used to diagnose active cases of COVID-19 can only indicate the presence of viral genetic material during the period of active infection and do not indicate if a person was infected and subsequently recovered.

What are some limitations of serology tests?

Unlike PCR-based tests that test for presence of the SARS-CoV-2 virus, serology tests cannot be used to diagnose whether someone currently has the COVID-19 disease. Also, antibody levels have not been correlated with immunity; while people who have been infected are presumed to have some immunity, it is unclear how much and for how long. Though labs that perform or companies selling tests to diagnose COVID-19 must receive Emergency Use Authorization (EUA) from the FDA, the FDA has granted regulatory discretion to companies that develop and market serology tests and does not require them to apply for an EUA. As a result, there has not been a formal evaluation of the performance of serology tests that are currently available. Some reports have raised concerns about the validity of serology tests currently being used. The NIH, FDA, CDC, and academic investigators are in the process of validating serology tests.

How long does it take to get test results?

Timely test results are important to inform clinical care and to support public health measures to control COVID-19. The sooner patients receive test results, the sooner infected individuals can be isolated, before they transmit their infection to others. And, the contacts of infected individuals can be traced and monitored so that they, too, can take preventive measures to avoid spreading the disease.

Currently, the time it takes to get testing results in the U.S. can vary based on several factors. Different testing technologies produce results in different time frames. For example, some testing machines promise results in <30 minutes, whereas some laboratory methods can take hours. If a health facility has to send a test out to a separate laboratory, it can take additional time due to transit – a day or more depending on how far the facility is from the laboratory. It may also take additional time to relay the test result to the healthcare provider and patient. Across the U.S., delays in testing due to shortages of testing supplies have been reported.

Do patients have to pay to get tested?

In March 2020, the U.S. Congress passed and the President signed into law the Families First Coronavirus Response Act, which requires governmental and private insurance plans to cover the cost of COVID-19 testing. The law does not protect against out-of-network charges or charges for visits for possible coronavirus infection that do not result in testing. While Congress set aside funds to test the uninsured, it is possible that some people without insurance will nonetheless be billed. The law does not cover the cost of COVID-19 treatment.

Where do people go to get tested?

Testing sites vary by state and locality. In some places, testing is only offered at health facilities and may be reserved for hospitalized patients. Some states have established community testing sites, such as drive-through testing clinics.

Why are there inconsistencies among testing data for COVID-19?

The website relies upon publicly available data from multiple sources that are not always consistent in how and when they are released and updated. States may report components of testing data with different cadences, or they may even change how they report categories of data over time, all of which can affect calculations of the rate of positivity. For example, some states report testing positives separately from testing negatives, which may make it appear that 100% of their tests were positive or 100% negative on that day. Also, states have changed how they count positives and negative test results and may retroactively change the numbers reported.

It is important to track the testing that states are doing to diagnose people with COVID-19 infection in order to gauge the spread of COVID-19 in the U.S. and to know whether enough testing is occurring. When states report the number of COVID-19 tests performed, this should include the number of viral tests performed and the number of patients for which these tests were performed. Currently, states may not be distinguishing overall tests administered from the number of individuals who have been tested. This is an important limitation to the data that is available to track testing in the U.S., and states should work to address it.

When states report testing numbers for COVID-19 infection, they should not include serology or antibody tests. Antibody tests are not used to diagnose active COVID-19 infection and they do not provide insights into the number of cases of COVID-19 diagnosed or whether viral testing is sufficient to find infections that are occurring within each state. States that include serology tests within their overall COVID-19 testing numbers are misrepresenting their testing capacity and the extent to which they are working to identify COVID-19 infections within their communities. States that wish to track the number of serology tests being performed should report those numbers separately from viral tests performed to diagnose COVID-19.