Can a Quantitative Assessment of SARS-CoV-2 PCR Predict Degree of Severity and Outcomes in Critical Care Patients with COVID-19

Abstract

Real-Time polymerase chain reaction (qPCR) is the gold standard diagnostic method for acute SARS-CoV-2 infection. Cycle threshold (Ct) is defined as the number of heating and cooling cycles required during the PCR process. Ct-values are inversely proportional to the amount of target nucleic acid in a sample. Our aim in this retrospective study was to determine the impact of serial SARS-CoV-2 qPCR Ct-values, among critically ill COVID-19 patients both prior and during intensive care unit (ICU) stay, on: mortality, need for mechanical ventilation (MV) and development of acute kidney injury (AKI). There was a continuous increment in Ct-values over the ICU stay from 1st-week through to 3rd-week. Although not significant, lower ICU 1st-week Ct-values were associated with Black ethnicity, increased need for MV and mortality. However, patients who had developed AKI at any stage of their illness had significantly lower Ct-values compared to those with normal renal function. When ICU 1st-week Ct-values are subcategorised as <20, 20-30 and >30 the 28-day survival probability was less for patients with Ct-values of <20.To our knowledge this is the first report showing the impact of Ct-values and outcomes, especially AKI, among patients at different time point’s prior to and during ICU stay.