Cases don't equate infections.
"PCR detection of viruses is helpful so long as its limitations are understood; while it detects RNA in minute quantities, caution needs to be applied to the results as it often does not detect the infectious virus. This detection problem is ubiquitous for RNA viruses detection. SARS-CoV, MERS, Influenza Ebola and Zika viral RNA can also be detected long after the disappearance of the infectious virus.
Why does this matter? Because when it comes to Covid-19, insufficient attention has been paid to how PCR results actually relate to disease. The harms of false-positive results can be substantial: operations can be delayed or cancelled; patients are kept in hospital, just in case; further testing is required; in some cases, it drives local lockdowns. The results of our recent systematic review on viral infectiousness indicate that cycle thresholds are essential to understand who is infectious, and consequently, the extent of any outbreak and for controlling transmission.
When it comes to dealing with this ongoing pandemic, it is clear that Covid-19 – and our limited understanding of it – is testing our decision-making skills to the limit when it comes to diagnosing infections. And without a better understanding of what test results really show us, it seems that while coronavirus is at a low prevalence in our communities, mass testing might cause more harm than good if the nuances of test threshold are not understood.
WRITTEN BY
Prof Carl Heneghan & Tom Jefferson
Carl Heneghan is professor of evidence-based medicine at the University of Oxford and director of the Centre for Evidence-Based Medicine Tom Jefferson is a senior associate tutor and honorary research fellow at the Centre for Evidence-Based Medicine, University of Oxford"
https://www.spectato...harm-than-good-