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. 2022 Jan;94(1):240-245.
doi: 10.1002/jmv.27307. Epub 2021 Sep 15.

High proportion of low cycle threshold value as an early indicator of COVID-19 surge

Baijayantimala Mishra  1 , Jai Ranjan  1 , Prashanth Purushotham  1 , Swarnatrisha Saha  1 , Poesy Payal  1 , Punyatoya Kar  1 , Sivasankar Das  1 , Vaishnavi Deshmukh  1
Affiliations

High proportion of low cycle threshold value as an early indicator of COVID-19 surge

Baijayantimala Mishra et al. J Med Virol. 2022 Jan.

Abstract

Many countries in the world are experiencing a recent surge in COVID-19 cases. This is mainly attributed to the emergence of new SARS-CoV-2 variants. Genome sequencing is the only means to detect the evolving virus mutants and emerging variants. Cycle threshold values have an inverse relationship with viral load and lower Ct values are also found to be associated with increased infectivity. In this study, we propose to use Ct values as an early indicator for upcoming COVID-19 waves. A retrospective cross-sectional study was carried out to analyze the Ct values of positive samples reported during the first wave and second wave (April 2020-May 2021). Median Ct values of confirmatory genes were taken into consideration for comparison. Ct values below 25, >25-30, and >30 were categorized as high, moderate, and low viral load respectively. Our study found a significantly higher proportion of positive samples with a low Ct value (<25) across age groups and gender during the second wave of the COVID-19 pandemic. A higher proportion of positive samples with a low Ct value (high viral load) may act as an early indicator of an upcoming surge.

Keywords: COVID-19; SARS-CoV-2; cycle threshold; surge; variants.

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Conflict of interest statement

The authors declare that there are no conflict of interests.

Figures

Figure 1
Figure 1
Month wise COVID‐19 positive cases
Figure 2
Figure 2
Ct values of COVID‐19 positive cases during 2020 and 2021. Ct, cycle threshold
Figure 3
Figure 3
Gender wise Ct value comparison in 2020 versus 2021. Ct, cycle threshold
Figure 4
Figure 4
Comparison of Ct value across age groups (confirmatory genes) 2020 and 2021. Ct, cycle threshold
Figure 5
Figure 5
Ct value of symptomatic and asymptomatic cases. Ct, cycle threshold
Figure 6
Figure 6
Comparison of the proportion of weekly Ct values in the first and second waves of COVID‐19. Ct, cycle threshold
See this image and copyright information in PMC

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