A lesson from COVID-19 on the dangers of using Cq to quantify nucleic acids



SARS-CoV-2 RNA quantities, measured by reverse transcription quantitative PCR (RT-qPCR), have been proposed to classify individuals at greater likelihood of spreading infection as well as performance targets for IVD development and approval. A recent study investigated the reproducibility of quantification cycles (Cqs) – also referred to as cycle threshold (Ct) or crossing point (Cp) – and how setting diagnostic cutoffs altered the clinical sensitivity of COVID-19 testing.


During this panel discussion, our expert panelists will discuss why the study recommends that Cq values not be used in this way and will leverage their lessons learned from the pandemic to improve SARS-CoV-2 measurements and promote reproducibility across labs worldwide. Topics will include measurement science (metrology) and units, the potential impact on diagnostic performance and the development of IVDs, how the measurement science assisted external quality assessment providers and how this work was able to support thresholding in a real clinical setting. The panelists will also discuss the potential clinical impact of their findings as well as explore how the performance of diagnostic tests may be linked to the stage of the pandemic. For instance, is it better to deploy analytically less sensitive tests as a screening tool when the pandemic is growing rather than when it is more stable or decreasing?



Professor Jim Huggett

Science Fellow
UK National Measurement Laboratory, LGC


Kathryn Harris

Consultant Clinical Scientist
Royal London Hospital, Barts Health NHS Trust


Professor Heinz Zeichhardt

Professor of Virology
Charité – University Medicine Berlin

Watch now

Fill out this simple form and
get immediate access: