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The IDSA (Infectious Diseases Society of America) panel has
updated guidelines on coronavirus disease (COVID-19) molecular diagnostic
tests.
According to the IDSA panel updates guidelines on COVID-19 molecular diagnostic tests, the saliva tests are especially effective if the test instructs to cough or clear the throat before spitting into tube. It was found that in comparison with other methods, the usage of a throat swab alone had less efficacy and missed more cases.
Compared to throat swab alone, a saliva test or swabs from either middle or front of nose are favored when. In comparison with the gold-standard deep swab, the combination of saliva and swabs from the front and middle of nose and throat together are comparable. However, the multiple swabs worsen the already challenging supply issues.
Saliva samples are accompanied by several challenges. A lab should authenticate that its systems can suitably deal with the stickier materials. Requesting a patient to cough needs more personal protective equipment (PPE) for the medical care professional. Each center needs to tailor type of sample it selects, on the basis of availability of resources and setting (in a hospital or a drive-through operation).
Compared to the rapid isothermal test, the rapid polymerase chain reaction (PCR) tests and standard laboratory-based PCR tests are favored. Rapid tests were specified as tests for which there is availability of results within one hour after a test provider has the sample. Home tests were not included for this category.
The only quick isothermal test that had sufficient data on
which to publish a recommendation was ID NOW test. Rapid PCR tests were found
to display comparable performance compared to the standard laboratory-based
tests. It also illustrated a very high specificity and high sensitivity of 97% on average.
However, rapid isothermal test had a mean sensitivity of only 80% in comparison with laboratory-based PCR test, offering numerous false-negative outcomes.
The testing centers will have to weigh the significant profit of procuring results in 15 min utilizing a quick isothermal test and awaring positive individuals about instant isolation against the potential for false negatives, which may send positive subjects to home believing they don't have COVID-19 and therefore substantially spread the infection.
A backup test with a prompt PCR or laboratory-based test should be used if a physician obtains negative result with isothermal test, but is highly suspicious that the individual has COVID or resides in the area with greater prevalence of infection. A certain proportion of subjects utilizing this isothermal test may be missed. If isothermal test is the only available choice, it should be utilized because it is certainly better compared to not testing at all.
All the test varieties have higher specificity, several
false-positive results might not be seen.
Due to paucity of data in the literature, the previous guidelines didn't make any recommendations on rapid tests. The major available data were for symptomatic individuals. However few data demonstrate that amount of virus in respiratory tract is comparable for individuals with and without symptoms. The panel, thus, anticipates that performance of various assays would be comparable whether or not an individual had symptoms.
Previous guidelines advocated molecular testing for asymptomatic individuals who were waiting for a transplant or were waiting to initiate immunosuppressives for cancer or an autoimmune disorder. In these cases, the IDSA guidelines does not advocate for or against screening the immunocompromised individuals.
Due to the raised risks that will result if individuals have contracted the virus, individuals waiting for bone marrow and solid organ transplants should undergo testing. For patients suffering from an autoimmune disease or cancer, the guidelines advocate to leave it up to each clinician to determine the individual risk and assess whether testing of the patient should be done.
The home testing was not weighed in by IDSA guidelines. This is because the products are so novel and studies so far have incorporated less than 200 participants. In early phase of the disease (the initial 5-7 days) when the virus amount is elevated, they certainly perform better.
Majority of tests are EUA-authorized. Moreover, it doesn't
look like this novel variant should really impact the test performance. The
current tests would not be impacted because the variant has considerable
differences in spike gene, and the various current tests recognize the virus
without the spike gene.
Medscape Pharmacists
IDSA Panel Updates Guidelines on COVID Molecular Diagnostic Tests
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