Viral RNA load as determined by cell culture for SARS-CoV-2 patients

Viral RNA load as determined by cell culture for SARS-CoV-2 patients. Jefferson T, Heneghan C.

https://www.cebm.net/study/viral-rna-load-as-determined-by-cell-culture-for-sars-cov-2-patients/

Published on July 30, 2020

Reference La Scola, B., Le Bideau, M., Andreani, J. et al. Viral RNA load as determined by cell culture as a management tool for discharge of SARS-CoV-2 patients from infectious disease wards Eur J Clin Microbiol Infect Dis 39, 1059–1061 (2020). https://doi.org/10.1007/s10096-020-03913-9
Study type
Country France
Setting Unclear
Funding Details Agence Nationale de la Recherche (ANR, French National Agency for Research), by Région Provence-Alpes-Côte d’Azur, and by European funding FEDER PRIMI.
Transmission mode Droplets
Exposures

Bottom Line

There was a significant relationship between Cycle Threshold (Ct) value and culture positivity rate: samples with Ct values of 13–17 all had positive culture. Culture positivity rate decreased progressively according to Ct values to reach 12% at a Ct of 33.

Evidence Summary

There was a significant relationship between Ct value and culture positivity rate: samples with Ct values of 13–17 all had a positive culture. Culture positivity rate then decreased progressively according to Ct values to reach 12% at 33 Ct. No culture was obtained from samples with Ct > 34. The 5 additional isolates obtained after blind subcultures had Ct between 27 and 34, thus consistent with low viable virus load.

Of the 183 samples inoculated in the study period, 129 led to virus isolation. Of these 124 samples had detectable cytopathic effects between 24 and 96 h from the inoculum. 

What did they do?

The study was carried out in France in a reference hospital in Marseilles. From 4384 samples from 3466 patients, 611 SARS-CoV-2 isolates were identified from 1049 samples and were cultured. 183 samples testing positive by RT-PCR (9 sputum samples and 174 nasopharyngeal swabs) from 155 patients, were inoculated in cell cultures. SARS-CoV-2. RNA rtPCR targeted  the E gene.

Nasopharyngeal swab fluid or sputum samples were filtered and then inoculated in Vero E6 cells. All samples were inoculated between 4 and 10 h after sampling and kept at + 4 °C before processing. After centrifugation, they were incubated at 37 °C. They were observed daily for evidence of a cytopathogenic effect. Two subcultures were performed weekly and scanned by an electron microscope and then confirmed by specific RT-PCR targeting E gene

Study reliability

The study is large, but the details of the cases and the flow of samples is not explained. No relation to symptoms is reported

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Unclear No Yes Yes No

What else should I consider?

About the authors

Carl Heneghan

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Tom Jefferson

Tom Jefferson

Tom Jefferson is a senior associate tutor and honorary research fellow, Centre for Evidence-Based Medicine, University of Oxford.