In the ideal world, every person would get tested for COVID-19. We would then isolate the people who tested positive and the world would move on. That is assuming COVID-19 testing is 100% accurate!
What COVID-19 test is being used?
The primary test used is a nucleic acid-based test . This mean it is detecting the viral RNA in these samples. The test is not a rapid “point of care” test. Therefor it cannot be performed quickly at home or at a doctor’s office. It requires samples to be collected and shipped to labs with special equipment. The test uses a quantitative method of amplifying the viral nucleic acid in the sample to the point of being able to measure it. It usually takes about 24 hours from the time of sample collection to the final test result, but times can vary. There is the push for a point of care test thereby giving near immediate results. There has also been a rumor of at home testing which is not anticipated soon.
Do we currently trust the COVID-19 test we have?
Our current test is a real-time RT-PCR test intended for the detection of nucleic acid from the 2019-nCoV in upper and lower respiratory specimens. There is no argument the US has lagged other advanced nations in COVID-19 testing. Former government officials/public health experts point to a series of decisions they say hindered the nation’s response to the pandemic. This includes the CDC’s attempt at creating their own test while preventing the release of other validated tests. Ultimately the test was flawed. To make matters worse, it is thought that some of the testing performed in China was only 43% accurate!
On February 29, FDA issued new guidance that allowed certain US labs to test for coronavirus using diagnostics. The labs developed and validated these tests. This was without the FDA reviewing them. It is understandable why the FDA has allowed this given the slow access to tests. On why it issued new guidance, the FDA said that “under the current circumstances, which are unlike any prior emergency we have seen, we think the benefit of access to certain tests outweigh the risks associated with launching tests prior to FDA review.”
Is sensitivity or specificity better for a killer virus?
This may not be comforting as there are not the typical checks and balances to validate accuracy. It is somewhat disturbing we do not know exact sensitivity and specificity of these tests. As a result, this means it may come back positive in some people who are not infected with SARS-CoV-2 and negative in some people who are. If partial to wanting a higher sensitivity vs. higher specificity for a killer virus, it would be prudent to have a test more sensitive. The less likely it will miss real cases. At this time we will have to trust the companies providing the tests have done their job. Time will tell. The real numbers of sensitivity and specificity will be known in the future but may be fuzzy now.
How can we maximize the sensitivities?
This circles back to the specimen sample. If the test is the wild card, it makes the SPECIMEN COLLECTION VERY IMPORTANT. Remember, for this virus we are looking to do anything we can to maximize the sensitivity. The test is only as good as the specimen collected. If an adequate viral load is not collected with the specimen sample, the test cannot detect it.
Nasopharyngeal aspirate gives the highest sensitivities of all previously known viruses. If our goal is to accurately diagnose our patients suspected of having COVID-19, we should provide them with the best sample that results in the most accurate test. A nasopharyngeal aspiration is the answer.