according to the Infectious Diseases Society of America (IDSA).
“Based on what we know about influenza, it’s unlikely that all of these tests are going to perform exactly the same way,” said, executive vice chair of the department of medicine at Brown University in Providence, R.I., at a press briefing. Although these tests are good, no test is perfect, she added.
The development and availability of testing has improved over time, but clinical laboratories still face challenges, said, associate professor of internal medicine at University of Utah, Salt Lake City. These challenges include shortages of devices for specimen collection, media, test tubes, and reagents. Although the goal is to test all symptomatic patients, these shortages require laboratories to prioritize health care workers and the sickest patients.
Tests are being approved through an abbreviated process
Two types of test, rapid tests and serology tests, are in use. Rapid tests use polymerase chain reactions to detect the virus in a clinical specimen. This type of testing is used to diagnose infection. Serology tests measure antibodies to the virus and are more appropriate for indicating whether a patient has been exposed to the virus.
The declaration of a national emergency enabled the FDA to activate its EUA policy, which allows for quicker approval of tests. Normally, a test must be assessed in the laboratory (such as with a mock specimen or an inactivated virus) and in a clinical study of patients. Under the EUA, clinical assessment is not required for the approval of a test. Consequently, the clinical performance of a test approved under EUA is unknown.
Collecting a specimen of good quality is critical to the quality of the test result, said Dr. Caliendo, the secretary of IDSA’s board of directors. Clinicians and investigators have used nasopharyngeal swabs, sputum, and specimens collected from deep within the lung. “We’re still collecting data to determine which is the best specimen type.” As coronavirus testing expands, particularly to drive-through testing sites, “we may be using people who are not as experienced, and so you might not get as high a quality specimen in that situation,” Dr. Caliendo added.
The timing of the test influences the quality of the result, as well, because the amount of virus is lower at the onset of symptoms than it is later. Another factor that affects the quality of the results is the test’s sensitivity.
The time to obtain results varies
The value of having several tests available is that it enables many patients to be tested simultaneously, said Dr. Hanson, a member of IDSA’s board of directors. It also helps to reduce potential problems with the supply of test kits. A test manufacturer, however, may supply parts of the test kit but not the whole kit. This requires the hospital or laboratory to obtain the remaining parts from other suppliers. Furthermore, test manufacturers may need to prioritize areas with high rates of infection or transmission when they ship their tests, which limits testing in other areas.
One reason for the lack of a national plan for testing is that the virus has affected different regions at different times, said Dr. Caliendo. Some tests are more difficult to perform than others, and not all laboratories are equally sophisticated, which can limit testing. It is necessary to test not only symptomatic patients who have been hospitalized, but also symptomatic patients in the community, said Dr. Caliendo. “Ideally, we’re going to need to couple acute diagnostics [testing while people are sick] with serologic testing. Serologic testing is going to be important for us to see who has been infected. That will give us an idea of who is left in our community who is at risk for developing infection.”
How quickly test results are available depends on the type of test and where it is administered. Recently established drive-through clinics can provide results in about 30 minutes. Tests performed in hospitals may take between 1 and 6 hours to yield results. “The issue is, do we have reagents that day?” said Dr. Caliendo. “We have to be careful whom we choose to test, and we screen that in the hospital so that we have enough tests to run as we need them.” But many locations have backlogs. “When you have a backlog of testing, you’re going to wait days, unfortunately, to get a result,” said Dr. Caliendo.
Dr. Caliendo and Dr. Hanson did not report disclosures for this briefing.