Predicting Infectious Severe Acute Respiratory Syndrome Coronavirus 2 From Diagnostic Samples. (22nd May 2020)

• Record Type: Journal Article
• Authors: Bullard, Jared; Dust, Kerry; Funk, Duane; Strong, James E; Alexander, David; Garnett, Lauren; Boodman, Carl; Bello, Alexander; Hedley, Adam; Schiffman, Zachary; Doan, Kaylie; Bastien, Nathalie; Li, Yan; Van Caeseele, Paul G; Poliquin, Guillaume
• Is Part Of: Clinical infectious diseases. Volume 71:Number 10(2020)
• Page Start: 2663
• Page End: 2666
• Publication Date: 2020-05-22
• Subjects: SARS-CoV-2 -- COVID-19 -- RT-PCR -- infectivity -- public health; Communicable diseases -- Periodicals; 616.905
• DOI: 10.1093/cid/ciaa638
• Languages: English
• ISSNs: 1058-4838

Abstract

Abstract: Background: Reverse-transcription polymerase chain reaction (RT-PCR) has become the primary method to diagnose viral diseases, including severe acute respiratory syndrome coronavirus 2 (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 tissue culture infectious dose/mL was 1780 (interquartile range, 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 (OR) for positive viral culture of 0.64 (95% confidence interval [CI], .49–.84; P < .001) for every 1-unit increase in Ct. Area under the receiver operating characteristic curve for Ct vs positive culture was OR, 0.91 (95% CI, .85–.97; P < .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. Abstract : Respiratory samples from COVID-19 patients with > 8 days of symptoms and a SARS-CoV-2 E gene reverse-transcription polymerase chain reaction cycle threshold value > 24 may predict lack of infectivity of those patients in a clinical and community context.