Science of Testing
Health Canada has finally approved a rapid COVID 19 detection test. Furthermore, the Federal Government of Canada has ordered almost $8 million of these tests.
It is using an existing technology by Abbott called, ID NOW. It is one of the most widely available molecular point-of-care testing technologies in use in the U.S. Since its introduction in 2014, it has been used in physicians’ offices and urgent care centers to rapidly detect influenzas A & B, strep A, and respiratory syncytial virus (RSV). And now, it’s able to detect COVID-19.
Excerpt from May 2020 Press Release by Abbott Laboratories
“We’re seeing studies being conducted to understand the role of ID NOW in ways that it was not designed to be used. In particular, the NYU study results are not consistent with other studies. While we’ve seen a few studies with sensitivity performance percentages in the 80s, we’ve also seen other studies with sensitivity at or above 90%, and one as high as 94%.”
The SD Biosensor test is simpler and easier to use than the ABBOTT system because it does not require a ID NOW device. It can be administered by healthcare professionals but if necessary, can be self-administered in the safety and comfort of one’s workplace or home.
Sensitivity – 84.38%
Specificity – 100%
This dry blood spot test is simple, but yet, very accurate with a lower volume of blood needed and can be self-performed in the comfort of your home. This methodology allows for blood collection without the risk of cell hemolysis which means recollection is required. The dry blood spot is reconstituted using a buffer at the lab and the serum is tested using either the ECLIA and/or ELISA methodology.
Traditionally, one SST blood tube needs to be drawn in person at a lab where the red cells are separated from the serum using a centrifuge. Only a few drops of serum are then tested using the ELISA methodology.
Qualitative Detection of Antibodies Against COVID-19
The Elecsys® Anti-SARS-CoV-2 immunoassay is an in vitro test, using human serum and plasma drawn from a dry blood sample, to detect antibodies and determine the body’s immune reaction to SARS-CoV-2.
This serological assays can contribute to the identification of individuals exposed to the virus and assess the extent of exposure.
Elecsys® Anti-SARS-CoV-2 is an immunoassay for the in vitro qualitative detection of antibodies (including IgG) to SARS-CoV-2 in human serum and plasma.
20 μL* / 12 μL** of the patient sample are incubated with a mix of biotinylated and ruthenylated nucleocapsid (N) antigen. Double-antigen sandwich immune complexes are formed in the presence of corresponding antibodies.
After addition of streptavidin-coated microparticles, the DAGS complexes bind to the solid phase via interaction of biotin and streptavidin.
The reagent mixture is transferred to the measuring cell, where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are subsequently removed. Electrochemilumi-nescence is then induced by applying a voltage and measured with a photomultiplier. The signal yield increases with the antibody titer.
Drop™ COVID-19 IgG and IgM Antibodies Testing
(for licensed health professional office use only)
This antibodies test is useful for the detection of individuals who may have developed antibodies and are presumed immune to the SARS-CoV-2 virus.
Using a small blood sample, this test helps to detect recent past exposure to the SARS-CoV-2 virus by measuring the immune response to the infection. This is done by identifying IgM and IgG antibodies using ELISA methodology, the gold standard of laboratory antibodies testing.
An immune response can be detected approximately 1-2 weeks after infection in asymptomatic individuals and approximately 8-10 days after the onset of symptoms for those who have experienced fever and coughing.
RAPID Serologic Tests
At the moment, the true accuracy of RAPID serologic tests for SARS-CoV-2 is uncertain. In time, this may change as technology improves. The Food and Drug Administration (FDA) has granted an emergency use authorization (EUA) for a few antibody tests, the first one from Cellex, made in China. This test is 93.8% sensitive and 96.4% specific in testing on only 128 samples from Chinese COVID-19 patients confirmed by molecular genetic testing using RT-PCR. Other tests show a sensitivity rate as low as 80% (false negative of 20%).
The EUA allows a company to market unapproved diagnostic and therapeutic products during a declared emergency. According to “Policy D,” serologic tests for SARS-CoV-2 can be marketed and sold to clinical labs and hospitals as long as manufacturers have generated some level of validation data, even though the FDA has not reviewed the data.
Challenges of COVID-19 Testing
Dr. Sanjay Gupta, Chief Medica Correspondent, CNN
Canadian Antibody Testing Report
Avis Favaro, Medical Correspondent, CTV National News