Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences (The First Department of Internal Medicine), Fukuoka, Japan.
Department of Clinical Immunology, Rheumatology, and Infectious Disease, Kyushu University Hospital, Fukuoka, Japan.
Microbiol Spectr. 2024 Nov 5;12(11):e0093224. doi: 10.1128/spectrum.00932-24. Epub 2024 Oct 9.
Evaluating SARS-CoV-2 viral loads in nasopharyngeal (NP) and saliva samples, factors affecting viral loads, and the performance of rapid antigen testing (RAT) have not been comprehensively conducted during SARS-CoV-2 Omicron epidemic. This prospective study included outpatients enrolled during Omicron variant period in Japan. Paired NP swab and saliva samples were collected to measure viral loads by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The correlation between viral loads and clinical symptoms was examined. The performance of an immunochromatography-based RAT kit was also assessed. A total of 153 patients tested within 3 days of symptom onset were included. The mean viral load was 5.60 log copies/test and 3.65 log copies/test in NP and saliva samples, respectively, resulting in a significant difference ( < 0.0001). Fever over 37°C (axillary temperature) and total number of symptoms other than fever were identified as independent factors positively correlated with the viral loads in both NP and saliva samples. RAT sensitivity using NP and saliva samples was 92% and 68%, respectively, using positive RT-qPCR results as the reference. The sensitivity of RAT using NP and saliva samples was significantly higher in patients with fever ≥37°C and/or at least one symptom than in those with fever <37°C and/or no symptoms (97% vs 83% in NP swabs; 80% vs 50% in saliva). Distinct symptoms, including fever ≥37°C, may reflect high Omicron variant viral loads. Rapid antigen testing, not only using nasopharyngeal swabs but also using saliva, would be useful for COVID-19 diagnosis as point-of-care testing, particularly for symptomatic patients.
We examined nasopharyngeal and salivary viral loads using samples collected from outpatients with SARS-CoV-2 infection during the Omicron epidemic in Japan and explored the outpatient factors correlated with viral loads. In addition, we evaluated the performance of an authorized rapid antigen testing (RAT) kit using nasopharyngeal and saliva samples with RT-PCR testing as the reference. Intriguingly, a correlation between fever and other symptoms and SARS-CoV-2 viral loads in nasopharyngeal and saliva samples was observed based on one COVID-19 outpatient visit. RAT sensitivity was influenced by viral loads. Nevertheless, nasopharyngeal RAT is considered useful for SARS-CoV-2 point-of-care diagnosis. In patients with distinct symptoms, including high-grade fever, salivary RAT could be a practical diagnostic tool because of the higher estimated viral loads. After the Omicron epidemic, outpatients with mild COVID-19 have become the main focus of diagnosis and treatment. Our study provides valuable information regarding the point-of-care diagnosis of these patients.
本研究在日本的奥密克戎变异株流行期间，对门诊患者采集的鼻咽（NP）和唾液样本进行了 SARS-CoV-2 病毒载量检测，评估了影响病毒载量的因素，以及快速抗原检测（RAT）的性能。
本前瞻性研究纳入了奥密克戎变异株流行期间的门诊患者。采集 NP 拭子和唾液样本，通过逆转录定量聚合酶链反应（RT-qPCR）测量病毒载量。检查了病毒载量与临床症状之间的相关性，并评估了一种基于免疫层析的 RAT 试剂盒的性能。
共纳入 153 例症状出现后 3 天内检测的患者。NP 和唾液样本的平均病毒载量分别为 5.60 log 拷贝/测试和 3.65 log 拷贝/测试，差异有统计学意义（<0.0001）。体温≥37℃（腋温）和除发热外的总症状数被确定为与 NP 和唾液样本病毒载量呈正相关的独立因素。以阳性 RT-qPCR 结果为参考，NP 和唾液样本的 RAT 敏感性分别为 92%和 68%。与体温<37℃和/或无症状的患者相比，体温≥37℃和/或有至少一个症状的患者使用 NP 和唾液样本的 RAT 敏感性显著更高（NP 拭子为 97% vs 83%；唾液为 80% vs 50%）。
本研究使用来自日本奥密克戎变异株流行期间门诊患者采集的样本，检测了 NP 和唾液中的 SARS-CoV-2 病毒载量，并探讨了与病毒载量相关的门诊因素。此外，我们评估了使用 RT-PCR 检测作为参考时，经授权的 RAT 试剂盒在 NP 和唾液样本中的性能。有趣的是，根据一次 COVID-19 门诊就诊，观察到了 NP 和唾液样本中发热与其他症状和 SARS-CoV-2 病毒载量之间的相关性。RAT 敏感性受病毒载量影响。然而，NP RAT 被认为对 SARS-CoV-2 即时护理诊断有用。在有明显症状（包括高热）的患者中，由于估计的病毒载量较高，唾液 RAT 可能是一种实用的诊断工具。奥密克戎流行后，轻症 COVID-19 患者已成为诊断和治疗的主要对象。本研究为这些患者的即时护理诊断提供了有价值的信息。
