Interpreting Diagnostic Tests for the Novel Coronavirus
A recent article in the Journal of the American Medical Association (JAMA) helps us interpret the tests done in Covid-19 illness. Thus far, the most reliable test for the diagnosis of Covid-19 illness has been the RT-PCR test of the nasal cavity secretions taken with a swab. This test can also be performed on swabs taken from the throat, the saliva, the sputum and even from stools. However, the results of secretions from the nasal cavity are most accurate and reliable. RT-PCR (reverse transcriptase polymerase chain reaction) is a genomic test that looks for the membrane or the nuclear proteins of the virus. To identify the presence of the virus from the tiny amount of the viral proteins picked up on the swab, the machine in the laboratory amplifies the genomic content by 20-60 or even 100-fold. Of course, if the viral load (the amount of virus and viral proteins) on the swab is high, then less amplification is needed for the RT-PCR test and vice versa. The journal...