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Abbott's New Rapid Test: Let's Pump the Brakes a Bit on the Excitement.

Updated: Sep 4, 2020

I have seen frequently on my social media feed the excitement surrounding Abbott's new rapid test. And clearly the markets agreed, as Abbott's stock increased by 8% as a result. So is the Abbott rapid test the answer to cure the huge backlog in cases and usher us into an era where we can safely gather once again in large groups, such as work, school, or sporting events? Based on what I have read and my understanding of the Abbott rapid test itself, I am skeptical. And I wanted to share my thoughts regarding the utility of this test because honestly what I have read in many press releases seem very misleading. Abbott got Emergency Use Authorization (EUA) recently by the FDA for their BinaxNOW COVID-19 Ag Card, a rapid point-of-care test which uses the same technology found in pregnancy tests.

It tests for a protein antigen unique to SARS-CoV-2 using less invasive nasal swab samples compared to the gold standard deep nasal swab. Abbott states it can be used as a first-line of defense to identify people who are currently infected and who should then isolate as a result. It is a test that can be performed by those with minimal training and a patient prescription that gives results in 15 minutes and only costs $5. Per Abbott, it carries a sensitivity of 97.1% and a specificity of 98.5% in patients SUSPECTED of COVID-19 by their health care provider within the first 7 days of symptom onset. HOWEVER, those numbers were determined by a total pool of 102 samples - not a very large number at all. But let's say for the sake of argument those numbers prove to be accurate. In the case of those who were symptomatic, this would DRAMATICALLY decrease the current turn-around time to obtain a result via PCR testing and thus minimize the time in quarantine if negative. This is obviously a good thing. But what if you were NOT symptomatic?  Well, this is less clear because, well, Abbott does NOT have the data yet to support the tests use in the asymptomatic population. And as a result, Abbott does NOT have FDA authorization to do so at this time. And if they ever do remains to be seen. Thus far, we only know the accuracy of the test is high when used in those WITH SYMPTOMS consistent with COVID. But many press releases seem to commonly mention the phrase “mass testing" in reference to this test when we do not yet know if this test, in fact, will ever be good enough to actually be used as an actual SCREENING test. Maybe it will. But maybe it will not. Because if this test provides numerous false positives and/or negatives when applied to the population as a whole, then its use will be EXTREMELY limited. Abbott is trying to collect the data regarding the efficacy of its test for the asymptomatic population at this time, but until they do, let's pump the brakes a bit: Remember the excitement for antibody tests? Those tests were NEVER meant to test the general population as a whole for antibodies, but only those with suspected or confirmed past infections of COVID. As people came to realize, the accuracy of the results can quickly go to shit when not used in the population it was intended or. This is VERY important: do NOT get caught up with seemingly "high" sensitivities and specificities of tests because those pretty numbers only apply under certain conditions. I encourage you to PLEASE go back and read my post below where I explained sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) in the context of antibody tests. By simply replacing the word antibody with the word antigen in the two examples I give, you will come to understand sensitivity and specificity values are characteristics of the test itself, and those values are ONLY met when the chance of being infected is high based on the prevalence of the disease within a population. The sensitivity and specificity of this test is VERY similar to my Diasorin example, and you can quickly see why this test may not be as great as it seems depending on the population it is testing: The numbers provided by Abbott assume a high prevalence of disease in its testing population due to the presence of symptoms highly consistent with COVID. Without these conditions and depending on the prevalence of the disease in the testing population, the PPV of these tests could be MUCH POORER resulting in NUMEROUS false positives. And since false positives in this case would lead many to quarantine unnecessarily, any positive test in this case would then have to be confirmed by PCR via a deep nasal swab to ensure its accuracy. In addition, the NPV may increase though this does not necessarily prove the person has not been infected by COVID - it may just mean they have not yet formed enough of the COVID antigen at the time of testing. Same as with the antibody tests. Main takeaway: TESTS SHOULD TEST THOSE FOR WHOM THE TEST WAS MADE. Simple. Given asymptomatic/pre-symptomatic spread is a huge concern, this test has not proven it is capable of tackling this segment of the population. And if it cannot, we are not any closer to addressing the need for a rapid and ACCURATE screening test for COVID in the general population.  But this could provide the blueprint for a test that could EVENTUALLY meet our needs. But we are not there yet. And until that occurs, PLEASE do NOT go running to your doctor asking them to write you a prescription for this test if you are asymptomatic. Do NOT use a possible negative test as an excuse to routinely not wear masks or social distance around others. Just as I plead to others, COVID history or not, to NOT use a positive antibody test as a security blanket. So in short: the test has its usefulness, but let’s ensure it is used for its intended purpose. And not anything more. #covid19 #abbottrapidtest #notallisasitseems

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