We continue to be bombarded by media and hearsay about COVID-19 testing. Hopefully this information may help offer some guidance regarding the testing issues and some direction for you to consider personal testing. There are two types of COVID 19 tests available at this time, the molecular testing for active disease and the antibody test for the exposure to or recovery from the disease.
The molecular test looks for active disease. This involves taking a cotton swab of one nostril for about a five second duration. This sample is then sent to the lab to undergo a polymerase chain reaction (PCR). This testing checks for the presence of the genetic material of the virus. A positive PCR test identifies the presence of two specific SARS-CoV-2 genes.
If there is only one gene present, the test is reported as an inconclusive result. This testing can only diagnose a current active case of COVID-19. Common symptoms include a cough and/or shortness of breath. At least two additional symptoms including fever/chills, muscle pain, headache, sore throat and loss of taste or smell are suspicious of disease. Some individuals may have only a few or no symptoms whatsoever, but still be actively infected. Negative test during the presence of acute respiratory symptoms indicates that the illness is not COVID-19.
False negative testing may occur if the test is collected too early in the exposure of the disease. The usual period from catching the infection to developing symptoms averages 5-6 days, but may be up to 14 days. During the “pre-symptomatic” period, some individuals may be actively spreading the infection.
At this writing, the only way to access local molecular testing is with a physician order through the Coconino County Health Department. The collection sites for testing are at Fort Tuthill and their King Street building, but schedules may vary. For more information and updates, visit www.coconino.az.gov/2294/COVID-19-Information.
Coronavirus COVID-19 SARS-CoV-2 Antibody IgG testing may show individuals who have recovered from exposure to COVID-19. This test searches for the presence of specific antibodies that the body has produced to fight the virus. A blood sample is needed to run this test, and there are a number of commercial labs producing these serologic tests. This testing should not be considered until at least ten days or longer after symptoms develop, as it can take one to three weeks for the body to develop antibodies.
A positive test shows that antibodies are present, a negative indicates no antibodies present. There are some questions that arise about such testing. By recent reports, some of these lab tests may be up to thirty percent inaccurate. False positives may indicate antibodies, but may not be specific to SARS-CoV-2 as there are other common Coronaviruses including HKU1, NL63, OC43 and 229E. There is also no distinction as to recovering from a present COVID-19 infection or a previous common non-SARS-CoV-2.
One needs to use some care in interpreting the value of antibody testing. There is no assurance that antibody positive individuals may continue to be resistant to future exposures. Or, if positive, for what longevity may their resistance be present. That said, the presence or absence of antibodies should not be used to definitively diagnose or exclude COVID-19 infection or designate the status of infection. Be careful about using these test results alone to make health related decisions. Because of these problems, some medical clinics are not offering this test to their patients. Consult your health care provider for guidance regarding testing during these challenging times.
Bradford Croft, DO
East Flagstaff Family Medicine