Virological surveillance of SARS-CoV-2 in an Italian northern area: comparison of Real Time RT PCR cycle threshold (Ct) values in three epidemic periods

Virological surveillance of SARS-CoV-2 in an Italian northern area: comparison of Real Time RT PCR cycle threshold (Ct) values in three epidemic periods

Authors

  • Licia Veronesi Department S.Bi.Bi.T, University of Parma
  • Maria Eugenia Colucci Department of Medicine and Surgery, University of Parma, Italy
  • Cesira Pasquarella Department of Medicine and Surgery, University of Parma, Italy
  • Luca Caruso Department of Medicine and Surgery, University of Parma, Italy
  • Mostafa Mohieldin Mahgoub Ibrahim Department of Medicine and Surgery, University of Parma, Italy
  • Roberta Zoni Department of Medicine and Surgery, University of Parma, Italy
  • Massimiliano Pergreffi Department of Medicine and Surgery, University of Parma, Italy
  • Carlo Arcuri Department of Medicine and Surgery, University of Parma, Italy
  • Chiara Seidenari Department of Medicine and Surgery, University of Parma, Italy
  • Isabella Viani Department of Medicine and Surgery, University of Parma, Italy
  • Emanuela Capobianco Department of Medicine and Surgery, University of Parma, Italy
  • Sandra Mezzetta Department of Medicine and Surgery, University of Parma, Italy
  • Paola Affanni Department of Medicine and Surgery, University of Parma, Italy

Keywords:

SARS-CoV-2, nasopharyngeal swab, Real-Time RT PCR, cycle threshold, surveillance

Abstract

Aim of the study was to investigate the differences in Ct values in nasopharingeal swabs collected in three SARS-CoV-2 epidemic periods: first one from February 23 to March 25 (14 days from lockdown started on March 11); the second one from  March  26 to May 18 (14 days  from the end of strict lockdown on May 4) and the third one from May 19 until June 15. Viral RNA was detected in nasopharyngeal swabs obtained both from inpatients and outpatients. COVID-19 infection was confirmed according to the Ct values for N1 and N2 genes ascertained by Real-Time RT-PCR assay as described by the CDC. We calculated the prevalence of nasopharyngeal swabs tested positive for SARS-CoV-2, the mean and median of the Cts and the percentage of samples equal or below the Ct value of 25 in the 3 periods considered. The average value of Ct increased, going from 24.80 in the first epidemic period to 26.64 in the second period to 28.50 in the third period (p <0.001). The percentage of samples with Ct lower than or equal to 25 also decreased sharply from 54.7% to 20.0%. These findings need to be integrated with epidemiological and clinical data.

References

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Published

20-07-2020

How to Cite

1.
Virological surveillance of SARS-CoV-2 in an Italian northern area: comparison of Real Time RT PCR cycle threshold (Ct) values in three epidemic periods. Acta Biomed [Internet]. 2020 Jul. 20 [cited 2024 Jun. 22];91(9-S):19-21. Available from: https://www.mattioli1885journals.com/index.php/actabiomedica/article/view/10138