One of the primary tools for diagnosing COVID-19 is the nucleic acid-based real-time reverse transcriptase-polymerase chain reaction (RT-PCR) test performed on respiratory specimens. The detection rate of SARS-CoV-2 in lower respiratory specimens (such as sputum) is higher than that for upper respiratory specimens (such as nasal and pharyngeal swabs). However, sputum specimens are usually quite viscous, requiring a homogenization process prior to nucleic acid (NA) extraction for RT-PCR. Sputum specimens from COVID-19 and non-COVID-19 patients were treated with four commonly used reagents—saline, N-acetyl-L-cysteine (NALC), proteinase K (PK), and dithiothreitol (DTT), prior to NA extraction. These reagents were then compared for their performance in diagnosing COVID-19 in real clinical practice. The detection rate of SARS-CoV-2 in PK- or DTT-treated sputum was comparable, and higher than that in sputum treated with NALC or saline. While there was a 4.8% (1/21) false negative rate for the PK- and DTT-treated sputum, neither treatment showed any false positive cases among patients with non-COVID diseases. Moreover, sputum pretreated with saline, NALC, PK or DTT showed higher detection rates of SARS-CoV-2 as compared to pharyngeal swabs. Taken together, we provide direct evidence recommending the use of PK or DTT to pretreat sputum samples to facilitate SARS-CoV-2 detection by clinical laboratories. Moreover, our methods should help to standardize the procedure of processing sputum specimens and improve the ability to detect SARS-CoV-2 in these samples.
【저자키워드】 COVID-19, sputum, detection of SARS-CoV-2, proteinase K (PK), DTT, 【초록키워드】 Treatment, SARS-CoV-2, Diseases, nasal, RT-PCR, nucleic acid, SARS-CoV-2 detection, False negative rate, swabs, Patient, False positive, detection rate, Clinical practice, Evidence, respiratory specimens, Sputum sample, specimen, help, pharyngeal, proteinase, diagnosing, reagent, while, homogenization, upper respiratory, IMPROVE, respiratory specimen, performed, detect, facilitate, treated, comparable, non-COVID-19 patient, 【제목키워드】 SARS-CoV-2, detection, clinical, dithiothreitol, Direct,