Journal
JOURNAL OF CLINICAL VIROLOGY
Volume 129, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.jcv.2020.104519
Keywords
SARS-CoV-2; Proteinase K; Detection; RT-PCR; COVID-19; Nucleic acid extraction
Categories
Funding
- Consultancy Service for Enhancing Laboratory Surveillance of Emerging Infectious Diseases and Research Capability on Antimicrobial Resistance for Department of Health of the Hong Kong Special Administrative Region Government
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Background: The severe shortage of nucleic acid extraction kits during the current COVID-19 pandemic represents a key limiting factor in testing capacity. Objectives: This study compared the results of SARS-CoV-2 RT-PCR using different simple nucleic acid extraction methods on nasopharyngeal and saliva specimens. Study design: Fifty nasopharyngeal swab and saliva specimens previously tested positive for SARS-CoV-2 were retrieved. Three different methods of nucleic acid extraction were compared. The first method involves incubating the specimen with proteinase K, and then heat treatment at 98 degrees C for 5 min (PKH); the second method involves heat treatment at 98 degrees C for 5 min without proteinase K pre-incubation (heat only); the third method involves no pre-processing steps (direct). The products from all 3 methods were tested by SARS-CoV-2 RT-PCR. Results: PKH had significantly higher positive rate in SARS-CoV-2 RT-PCR (80 %) than those of heat only (58 %; P = 0.001) or direct (56 %; P = 0.002). The median Ct value was significantly earlier for PKH (median Ct: 37.0, IQR 31.7-40) than that of heat only (median Ct: 40, IQR 36.2-41; P < 0.0001) and direct (median Ct, 37.5; IQR 33.9-41.0; P = 0.0049). Subgroup analysis showed that PKH had higher detection rate, lower limit of detection and earlier Ct values than the other two groups for both NPS and saliva specimens. Conclusions: PKH pre-processing resulted in the highest detection rate of SARS-CoV-2 by RT-PCR, and represents an alternative method for nucleic acid extraction when commercial extraction kits are not available.
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