Epidemiological Significance of SARS-CoV-2 RNA Dynamic in Naso-Pharyngeal Swabs

Abstract

From 16 March to 15 December 2020, 132,357 naso-pharyngeal/oropharyngeal swabs were collected in the province of Teramo, Abruzzo Region, Italy, and tested for the presence of SARS-CoV-2 genomic RNA by a commercially available molecular assay. A total of 12,880 swabs resulted positive. For 8212 positive patients (4.150 women and 4.062 men) the median age was statistically different between women (median: 49.55 ± 23.9 of SD) and men (median: 48.35 ± 23.5 of SD) while no differences were found in the comparison between the cycle threshold for the N protein-encoding gene (CT N) median values and gender. Differences were observed in the CT N gene median values of swabs collected from March to September as well as in the pairwise comparison between September and October and between November and December. The CT N gene median values observed in specific periods characterizing the SARS-CoV-2 epidemic in 2020 were also compared with the incidence of COVID-19 cases; a strong inverse correlation was highlighted (Pearson correlation coefficient = −0.978). Our findings confirm the usefulness of the CT N values as an indirect detection parameter to monitor viral loads in the population.

Utility of the cycle threshold in anticipating the next phase of the coronavirus disease 2019 (COVID-19) pandemic

“…5 That study demonstrated that by combining data from multiple cross sectional samples, population incidence can be estimated and longer-term incidence curves can be identified, without the use of more time and resource-intensive serologic surveillance studies. 5 The Pearson correlation coefficient in our study was similar to those of previous studies, 6 with an inverse relationship between Ct values and incident cases of SARS-CoV-2 hospitalization. Another study utilizing a larger number of Ct values showed a similar trend between Ct values and hospitalizations, with a Pearson correlation of −0.851 (P < .001).…”

“…3,4 Recent studies have evaluated the use of Ct values as a more accurate method for estimating the epidemiologic trajectory of this pandemic. 5,6 Preliminary data suggest that when Ct values are higher, the epidemic appears to be in a waning phase, whereas when Ct values are trending lower, the epidemic may be growing. 5,6 We examined the association between Ct values from specimens collected over time at a tertiary-care emergency department with weekly state hospitalizations to evaluate the utility of using Ct to estimate epidemiologic trends and anticipate the next phase of the pandemic.…”

Age and Sex Modulate SARS-CoV-2 Viral Load Kinetics: A Longitudinal Analysis of 1735 Subjects

“…However, the viral load decay speed was not significantly different between the cohorts, suggesting that the speed may be dependent on the basal viral load independently of the SARS-CoV-2 strain (Figure 2A,B). In line with this result, other studies evaluating the correlation between viral load and its decay over time found that higher amounts of virus detected in the nasooropharyngeal swabs were correlated to an increased viral persistence [27,28]. Moreover, the duration of the infection significantly differed between OSs carriers with different VLDS and these data were reinforced by the medium effect size obtained by comparing slow VLDS vs. medium/fast VLDS individuals (Supplementary Materials: Table S1).…”

Systematic Review on the Correlation Between SARS-CoV-2 Real-Time PCR Cycle Threshold Values and Epidemiological Trends

“…During two epidemic waves the peak in viral load (determined by Ct) preceded the peak in positivity by 2–3 weeks Calistri et al. [ 21 ] 2021 Italy To analyze the trend of the Ct values in samples collected from March to mid-December 2020 Real-time Local Local There was a strong inverse correlation between Ct values and the trend in incident cases in the local population El Zein et al. [ 16 ] 2021 USA To evaluate the role of Ct values in samples as a prognostic marker in hospitalized patients Retrospective cohort study Single unit/local Regional A steady decrease in the percent of positive samples determined by Ct values was associated with the evolution of the pandemic from April to June 2020 Hay et al.…”