At PentaBase, we apply Ct values as a method to determine if a sample is positive or negative in RT qPCR analyses of SARS-CoV-2. Here, you can read more about Ct values and RT qPCR analysis.
COVID-19
This is how your Ct values look in your test result
When you receive your PentaBase test result, it will reveal whether you have tested positive or negative for SARS-CoV-2 (COVID-19).
If you have tested positive, the test result will also show you three Ct values under the section "comments," The values from our PCR analysis may indicate the amount of virus copies that were found in your sample. If the Ct values are low, your sample revealed a high amount of virus copies, whereas high Ct values indicate a lower amount of virus copies in your sample. It will also inform you on which assay your test has been analysed on, FAST or ULTRA. The Ct-value varies depending on which assay your test result has been obtained on.
FAST: At PentaBase, we determine a test positive when the Ct values are below 41 for at least two SARS-CoV-2 viral genes or if one gene has a Ct value below 41 on two individual purifications with the application of our CoviDetect™ Fast assay. The viral genes are IP2, IP4 and E
ULTRA: Your test is considered positive if there are any signs of SARS-CoV-2 viral genes below Ct 40 in either two of the genes or one of the genes in two independent purifications when we use our CoviDetect™ Ultra assay. The viral genes are Nsp2, ORF8 and M.
Understand your Ct values
The sample is positive for SARS-CoV-2 when the Ct values are below 41 for at least two SARS-CoV-2 viral genes, or if one gene has a Ct value below 41 on two individual purifications with the application of our CoviDetect™ Fast assay. This is how results look from a positive test on our RT qPCR machine.
How does PentaBase test?
At PentaBase, we perform the RT qPCR analysis and have for many years applied our knowledge in cancer monitoring- and diagnostics. We have been able to apply that exact knowledge in the detection of SARS-CoV-2.
When PCR-testing for SARS-CoV-2, RNA is transcribed into DNA, and primers that bind to the virus DNA in the sample, are added to the test. These primers are designed to bind themselves to the specific genetic material in SARS-CoV-2 and therefore, they do not bind to other vira or genes.
Via this RT qPCR analysis, we use the Ct value as a semiquantitative measurement of the amount of RNA found in the sample.
(Ct value is the number of cycles that are necessary for identifying a virus in PCR).
What does Ct value mean?
The Ct value is the cycle threshold; the value depends on the quality of samples taken during the period of sickness and the specific PCR method applied.
Regarding the detection of SARS-CoV-2, the Ct value is a value we apply to determine whether a SARS-CoV-2 sample is positive or negative and for quality control.
At PentaBase, we test on the three different SARS-CoV-2 genes: IP2, IP4, and E gene. Therefore, positive test results will show the Ct values for these three genes.
The RT qPCR analysis is the golden standard of SARS-CoV-2 detection and is considered the most precise method used in practice.
Research on Ct-values
RT qPCR analysis is the golden standard within the field of SARS-CoV-2 detection, and therefore, it is considered the most precise method used in practice.
At PentaBase, we use a Ct value cut-off point of 41 as other studies have demonstrated how individuals with low virus infection (high Ct values) still may transmit. (Read about the study here)
Other researchers have also documented that the Ct values should be interpreted with caution as results may differ with the use of different testing machines and different swab methods. Samples from the same person can give different results depending on the machine, sample quality, and sample method. (Read about the study here)
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