Abstract
Objective: Detection of SARS-CoV-2 by oropharyngeal swabs (OPS) and nasopharyngeal swabs (NPS) is an essential method for coronavirus disease 2019 (COVID-19) management. It is not clear how detection rate, sensitivity, and the risk of exposure for medical providers differ in two sampling methods.Methods: In this prospective study, 120 paired NPS and OPS specimens were collected from 120 inpatients with confirmed COVID-19. SARS-CoV-2 nucleic acid in swabs were detected by real-time RT-PCR. The SARS-CoV-2 detection rate, sensitivity, and viral load were analyzed with regards NPS and OPS. Sampling discomfort reported by patients was evaluated.Results: The SARS-CoV-2 detection rate was significantly higher for NPS [46.7% (56/120)] than OPS [10.0% (12/120)] (P < 0.001). The sensitivity of NPS was also significantly higher than that of OPS (P < 0.001). At the time of sampling, the time of detectable SARS-CoV-2 had a longer median duration (25.0 vs. 20.5 days, respectively) and a longer maximum duration (41 vs. 39 days, respectively) in NPS than OPS. The mean cycle threshold (Ct) value of NPS (37.8, 95% CI: 37.0–38.6) was significantly lower than that of OPS (39.4, 95% CI: 38.9–39.8) by 1.6 (95% CI 1.0–2.2, P < 0.001), indicating that the SARS-CoV-2 load was significantly higher in NPS specimens than OPS. Patient discomfort was low in both sampling methods. During NPS sampling, patients were significantly less likely to have nausea and vomit.Conclusions: NPS had significantly higher SARS-CoV-2 detection rate, sensitivity, and viral load than OPS. NPS could reduce droplets production during swabs. NPS should be recommended for diagnosing COVID-19 and monitoring SARS-CoV-2 load.Chinese Clinical Trial Registry, number: ChiCTR2000029883.
Highlights
Coronavirus disease 2019 (COVID-19) has developed into a devastating pandemic
The SARS-CoV-2 detection rate was significantly higher for nasopharyngeal swabs (NPS) [46.7% (56/120)] than oropharyngeal swabs (OPS) [10.0% (12/120)] (P < 0.001)
The mean cycle threshold (Ct) value of NPS (37.8, 95% confidence intervals (95% CI): 37.0–38.6) was significantly lower than that of OPS (39.4, 95% CI: 38.9–39.8) by 1.6, indicating that the SARS-CoV-2 load was significantly higher in NPS specimens than OPS
Summary
As of April 20, 2020, there were 2,314,621 confirmed cases confirmed cases globally, and 157,847 people have lost their lives (1) This pathogen is a novel enveloped RNA beta coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (2). To obtain upper respiratory specimens, medical providers usually use oropharyngeal swabs (OPS) and nasopharyngeal swabs (NPS) (3). It is unclear how the detection rate and sensitivity differ in the two sampling methods. Wang et al (4) reported that the detection rate of SARS-CoV-2 was higher in nasal swabs [63% (5/8)] than in pharyngeal swabs [32% (126/398)] Another small sample study analyzed 17 patients in early stages of COVID-19 and found that a higher viral load was detected in the nose than in the throat (5). Larger sample studies are needed to investigate that NPS specimens are more sensitive than OPS specimens for SARS-CoV-2 detection
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