In this post I discuss the COVID-19 PCR viral testing.
There are two types of COVID-19 tests:
- The PCR viral test is to see if you currently have the COVID-19 infection
- In this post I discuss the PCR Viral Test
- This test is not perfect and is discussed in the excerpts below from the Curbsiders #217 Covid Post.
- The bottom line from the above resource: “False negative PCR testing for SARS-CoV-2 is common! Each patient must be evaluated based on symptoms, timing, and other relevant/available clinical information. Don’t assume that a negative PCR means the patient is free from infection.”
- In this post I discuss the PCR Viral Test
- The antibody test is to see if you have had the COVID-19 infections.
- Please see the CDC’s Interim Guidelines for COVID-19 Antibody Testing. This link will be continuously updated by the CDC as new information becomes available.
- The accuracy of any of the many different antibody tests for a past COVID-19 infection depends on both the sensitivity and specificity of the individual test and on the underlying prevalence of COVID-19 infections in that population
In this post I link to and excerpt from The Curbsiders‘ #217 COVID Cakes the Fourth: ACTT-1, Triple Therapy, PCR, Serology, JUNE 1, 2020 By TIMA KARGINOV.
Here are excerpts from the podcast shownotes about COVID-19 PCR Viral Testing:
PCR Testing and Viral Shedding
A polymerase chain reaction (PCR) is a method of selectively amplifying and measuring small portions of DNA using multiple cycles of warming and cooling to denature the DNA and a heat-tolerant DNA polymerase to copy the material. Real-time PCR (RT-PCR) is a quantitative PCR that uses the number of cycles to approximate the starting quantity of genetic material in relation to a reference. The PCR itself is specific and sensitive, but this test is limited by the quality of sample collected.
Kucira et al looked at 7 different studies and found that 67% of patients will test negative 4 days after exposure (i.e. one day prior to symptom onset), approximately 38% percent of patients will be negative on the first day of symptoms, and the lowest false negative rate is 3 days after symptom onset (20%). Prolonged viral shedding has been reported for up to 6 weeks, but no replication competent virus has been isolated after 10 days. The South Korean CDC released a report that suggests that individuals who have recovered from COVID-19, but still have a positive SARS-CoV-2 PCR did not infect new individuals.
BOTTOM LINE:
False negative PCR testing for SARS-CoV-2 is common! Each patient must be evaluated based on symptoms, timing, and other relevant/available clinical information. Don’t assume that a negative PCR means the patient is free from infection.
Now please see my post Have You Had A COVID-19 Infection – The COVID-19 Antibody Test.
