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.
Keywords: COVID-19; RT-PCR; SARS-CoV-2; Viral load; ddPCR.
© The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: email@example.com.
ddPCR: a more accurate tool for SARS-CoV-2 detection in low viral load specimens.Emerg Microbes Infect. 2020 May 22:1-30. doi: 10.1080/22221751.2020.1772678. Online ahead of print. Emerg Microbes Infect. 2020. PMID: 32438868
Comparison of throat swabs and sputum specimens for viral nucleic acid detection in 52 cases of novel coronavirus (SARS-Cov-2)-infected pneumonia (COVID-19).Clin Chem Lab Med. 2020 Apr 16:/j/cclm.ahead-of-print/cclm-2020-0187/cclm-2020-0187.xml. doi: 10.1515/cclm-2020-0187. Online ahead of print. Clin Chem Lab Med. 2020. PMID: 32301745
Dynamic profile of RT-PCR findings from 301 COVID-19 patients in Wuhan, China: A descriptive study.J Clin Virol. 2020 Jun;127:104346. doi: 10.1016/j.jcv.2020.104346. Epub 2020 Apr 11. J Clin Virol. 2020. PMID: 32361324 Free PMC article.
Prolonged viral shedding in feces of pediatric patients with coronavirus disease 2019.J Microbiol Immunol Infect. 2020 Mar 28:S1684-1182(20)30081-5. doi: 10.1016/j.jmii.2020.03.021. Online ahead of print. J Microbiol Immunol Infect. 2020. PMID: 32276848 Free PMC article. Review.
Features, Evaluation and Treatment Coronavirus (COVID-19).2020 Apr 6. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan–. StatPearls. 2020 Jan–. PMID: 32150360 Free Books & Documents. Review.
Cited by 1 article
RT-qPCR Testing of SARS-CoV-2: A Primer.Int J Mol Sci. 2020 Apr 24;21(8):3004. doi: 10.3390/ijms21083004. Int J Mol Sci. 2020. PMID: 32344568 Free PMC article.