Association between SARS-CoV-2 Viral Load and Patient Symptoms and Clinical Outcomes Using Droplet Digital PCR

Abstract

The association between nasopharyngeal (NP) SARS-CoV-2 viral loads and clinical outcomes remains debated. Here, we examined the factors that might predict the NP viral load and the role of the viral load as a predictor of clinical outcomes. A convenience sample of 955 positive remnant NP swab eluent samples collected during routine care between 18 November 2020 and 26 September 2021 was cataloged and a chart review was performed. For non-duplicate samples with available demographic and clinical data (i.e., non-employees), an aliquot of eluent was sent for a droplet digital PCR quantification of the SARS-CoV-2 viral load. Univariate and multivariate analyses were performed to identify the clinical predictors of NP viral loads and the predictors of COVID-19-related clinical outcomes. Samples and data from 698 individuals were included in the final analysis. The sample cohort had a mean age of 50 years (range: 19–91); 86.6% were male and 76.3% were unvaccinated. The NP viral load was higher in people with respiratory symptoms (p = 0.0004) and fevers (p = 0.0006). In the predictive models for the clinical outcomes, the NP viral load approached a significance as a predictor for in-hospital mortality. In conclusion, the NP viral load did not appear to be a strong predictor of moderate-to-severe disease in the pre-Delta and Delta phases of the pandemic, but was predictive of symptomatic diseases and approached a significance for in-hospital mortality, providing support to the thesis that early viral control prevents the progression of disease.

Association of SARS-CoV-2 viral load with abnormal laboratory characteristics and clinical outcomes in hospitalised COVID-19 patients

“…Consistent with studies of other variants, our results also suggested that the viral loads in Omicron infection had a clear relationship with the outcomes of hospitalised patients [ 22 , 35 ]. Of all participants, 10 patients eventually died, and more than half of them had an initial △Ct value less than zero.…”

Clinical Evaluation and Comparison of Two Microfluidic Antigenic Assays for Detection of SARS-CoV-2 Virus

“…Both kits appeared not able to detect positive samples with lower viral loads (Cycle threshold > 30). Considering that individuals with fever and respiratory symptoms showed higher nasopharyngeal SARS-CoV-2 viral loads in terms both of digital PCR (Viral load quantification) and qPCR (Ct values) than those without those symptoms [18,19], the antigenic tests abovementioned might provide a useful assay to screen symptomatic patients in critical settings. Moreover, the possibility to use the same instrument to read results obtained by both kits may provide the ability to rapidly switch between them according to the pandemic context (i.e., presence or absence of contemporary Flu peak and increase in SARS-CoV-2 infection) [20].…”

Nasopharyngeal SARS-CoV-2 viral load kinetics using digital PCR

“…Remnant samples were analyzed using digital PCR (dPCR). Full details of the analysis can be found in Hastie et al [ 20 ] and in the Supplementary Material. In brief, RNA was extracted from 140 μL of the UTM, and eluted from the QIAgen column with 60 μL of Buffer AVE. 1 μL of the RNA extraction was loaded into a reaction mix, droplets were generated using the BioRad QX200 Droplet Generator, and PCR was run overnight using BioRad's C1000 Touch thermal cycler.…”