During this COVID-19 outbreak, I have the dual roles of overseeing our hospital’s response to the pandemic and also of rounding in our ICU and taking care of COVID patients first-hand. One of issues that I struggle with in both of these roles is how accurate is our testing? Currently, we have 3 ways that we test for active COVID-19 infection: a nasopharyngeal swab for a rapid molecular test (made by Abbott Corporation), a nasopharyngeal swab for a PCR (polymerase chain reaction) test, and bronchoalveolar lavage fluid for a PCR test. We use the first two a lot and use the last one rarely. But do we have this backward?
The rapid molecular test by Abbott is very quick and our lab can have the results in < 1 hour. The criticism of this test is that it is less sensitive than the PCR tests so you can miss patients who are infected with COVID-19, particularly if they have mild symptoms or are asymptomatic.
The nasopharyngeal PCR test is currently considered the “gold standard” test for COVID-19. It appears to be more sensitive than the Abbott rapid test so it pick up more patients infected with the virus. However, it takes longer – 8-12 hours if your hospital does testing for it in-house and 2-3 days if it has to be sent to an outside lab. We primarily use this test if the Abbott rapid test is negative and we still clinically suspect COVID infection or if a patient without symptoms needs to be cleared of having the infection prior to undergoing an elective surgery.
The bronchoalveolar lavage (BAL) PCR test requires the patient to undergo bronchoscopy, an invasive procedure that requires sedating the patient and can put hospital staff at risk due to aerosolizing infected lung fluids into the air. Doing bronchoscopy on patients with suspected COVID-19 infection is generally discouraged because of the risk to the staff and the risk to the patient of an invasive procedure. Therefore, we don’t do a lot of BAL COVID tests.
Most respiratory viruses affect either the upper respiratory tract alone or both the upper and lower respiratory tract. The upper respiratory tract consists of the nose and throat; the lower respiratory tract consists of the lungs. COVID-19 is unusual among respiratory viruses in that it primarily causes symptoms in the lower respiratory tract resulting in cough, low oxygen, and shortness of breath. COVID generally does not cause much upper respiratory tract symptoms, such as sneezing or a runny nose.
So one has to wonder, if COVID does not affect the upper respiratory tract, how good is testing nasopharyngeal secretions? Most of us who care for patients with COVID infection have encountered patients who had 1 or more nasopharyngeal Abbott rapid tests or PCR tests that were negative only to have the 2nd or 3rd PCR test end up being positive. We are also now seeing patients who have multiple negative nasopharyngeal PCR tests who then get a bronchoscopy and their BAL COVID PCR test comes back positive.
We spend a lot of energy debating whether the nasopharyngeal Abbott rapid or the PCR test is the best test. But maybe we ought to be asking whether the BAL is really the best test. When asked why he robbed banks, Willie Sutton famously said “Because that’s where the money is”. For those patients who present to the hospital with COVID-like signs & symptoms but have a negative nasopharyngeal PCR test, we may need to start doing more bronchoscopies with BAL COVID testing before pronouncing those patients virus-free.
May 17, 2020