Predicting infectious SARS-CoV-2 from diagnostic samples

By J. Bullard, Kerry Dust, D. Funk, J. Strong, D. Alexander, L. Garnett, Carl Boodman, A. Bello, A. Hedley, Zachary Schiffman and 5 more. Clinical Infectious Diseases, 2020

873 citations recorded by the source corpus.

Abstract Background RT-PCR has become the primary method to diagnose viral diseases, including SARS-CoV-2. RT-PCR detects RNA, not infectious virus, thus its ability to determine duration of infectivity of patients is limited. Infectivity is a critical determinant in informing public health guidelines/interventions. Our goal was to determine the relationship between E gene SARS-CoV-2 RT-PCR cycle threshold (Ct) values from respiratory samples, symptom onset to test (STT) and infectivity in cell culture. Methods In this retrospective cross-sectional study, we took SARS-CoV-2 RT-PCR confirmed positive samples and determined their ability to infect Vero cell lines. Results Ninety RT-PCR SARS-CoV-2 positive samples were incubated on Vero cells. Twenty-six samples (28.9%) demonstrated viral growth. Median TCID50/ml was 1780 (282-8511). There was no growth in samples with a Ct > 24 or STT > 8 days. Multivariate logistic regression using positive viral culture as a binary predictor variable, STT and Ct demonstrated an odds ratio for positive viral culture of 0.64 (95% CI 0.49-0.84, p<0.001) for every one unit increase in Ct. Area under the receiver operating characteristic curve for Ct vs. positive culture was OR 0.91 (95% CI 0.85-0.97, p<0.001), with 97% specificity obtained at a Ct of >24. Conclusions SARS-CoV-2 Vero cell infectivity was only observed for RT-PCR Ct < 24 and STT < 8 days. Infectivity of patients with Ct >24 and duration of symptoms >8 days may be low. This information can inform public health policy and guide clinical, infection control and occupational health decisions. Further studies of larger size are needed.

Subfields: Infectious Diseases

View Paper: https://www.semanticscholar.org/paper/aabdf910e55cf6d3a84d43a13bd315441e2a8510

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Citations in the corpus

Duration of infectiousness and correlation with RT-PCR cycle threshold values in cases of COVID-19, England, January to May 2020 (2020, result): “The findings concur with smaller studies that identified infectious virus shed for 8 or 9 days [5-9] and others demonstrating correlation between Ct value/viral load and cultivable virus [5,9-11].”