The growing number of FDA-approved tests (so far about 25 tests have been approved), the confusion as well as intentional & unintentional misinformation is also spreading in the news & social media. Thus, it’s important clarify some facts & to distinguish the two type of tests so far available in the USA:
- Direct detection of SARS-CoV-2 (the new official name of the virus) which causes COVID-19 (corona virus disease 2019): These tests detect the viral RNA fragments in the mucus secretion (obtaining by upper respiratory tract swabs that are inherently prone to error) or in the blood (more reliable & accurate). These biochemical methods usually involve PCR (polymerase chain reaction) tests that could be performed, until recently, only in specialized molecular pathology labs. At the end of March 2020, the FDA approved a very rapid PCR test that can be performed in office/desktop type ID NOW instruments produced by Abbott Labs. These instruments are in common use to detect influenza & other viral or bacterial products. With this technique positive results can be seen in 5 mins, negative ones in 13 mins. To measure the viral RNA in the blood, samples still must be sent to specialized labs.
- Measuring the antibodies against SARS-CoV-2 in the plasma, obtaining by centrifugation the venous blood samples. These tests do NOT detect the virus, only our antibodies that develop in few days or weeks after the exposure, irrespective if a person is sick, or asymptomatic. Positive results may also indicate that the patient is immune to this virus. This is the medical reason why people with defective or drug-suppressed immune system are so susceptible to COVID-19, i.e., since they cannot develop antibodies against the virus.
It’s also important to understand that there is no such thing as “drive-through testing” – only drive-through sample collection (of swabs) that need to be sent to specialized lab., where the results may be ready in 2-4 days.