Clin Infect Dis. Quantitative Detection and Viral Load Analysis of SARS-CoV-2 in Infected Patients

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Clin Infect Dis. 2020 Mar 28. pii: ciaa345. doi: 10.1093/cid/ciaa345. [Epub ahead of print]
Quantitative Detection and Viral Load Analysis of SARS-CoV-2 in Infected Patients.


Yu F^1,2, Yan L^1,2, Wang N^3,4, Yang S^1,2, Wang L^1,2, Tang Y^1,2, Gao G^1,2, Wang S^1,2, Ma C^1,2, Xie R^1,2, Wang F⁵, Tan C⁵, Zhu L³, Guo Y⁵, Zhang F^1,2.

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Abstract

BACKGROUND:

Coronavirus disease 2019 (COVID-19) has become a public health emergency. The widely used reverse transcription PCR (RT-PCR) method has limitations for clinical diagnosis and treatment.
METHODS:

A total of 323 samples from 76 COVID-19 confirmed patients were analyzed by droplet digital PCR (ddPCR) and RT-PCR based two target genes (ORF1ab and N). Nasal swabs, throat swabs, sputum, blood, and urine were collected. Clinical and imaging data were obtained for clinical staging.
RESULTS:

In 95 samples tested positive by both methods, the cycle threshold (Ct) of RT-PCR was highly correlated with the copy numbed of ddPCR (ORF1ab gene, R2 = 0.83; N gene, R2 = 0.87). 4 (4/161) negative and 41 (41/67) single-gene positive samples tested by RT-PCR were positive according to ddPCR with viral load ranging from 11.1 to 123.2 copies/test. Then the viral load of respiratory samples was compared and the average viral load in sputum (17429 ? 6920 copies/test) was found to be significantly higher than in throat swabs (2552 ? 1965 copies/test, p < 0.001) and nasal swabs (651 ? 501 copies/test, p < 0.001). Furthermore, the viral load in the early and progressive stages were significantly higher than that in the recovery stage (46800 ? 17272 vs 1252 ? 1027, p < 0.001) analyzed by sputum samples.
CONCLUSIONS:

Quantitative monitoring of viral load in lower respiratory tract samples helps to evaluate disease progression, especially in cases of low viral load.
? The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.



KEYWORDS:

COVID-19; RT-PCR; SARS-CoV-2; Viral load; ddPCR


PMID:32221523DOI:10.1093/cid/ciaa345