Department of Environmental Health, Boston University School of Public Health, Boston, Massachusetts, United States of America.
Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America.
PLoS One. 2022 Jul 13;17(7):e0270694. doi: 10.1371/journal.pone.0270694. eCollection 2022.
At our university based high throughput screening program, we test all members of our community weekly using RT-qPCR. RT-qPCR cycle threshold (CT) values are inversely proportional to the amount of viral RNA in a sample and are a proxy for viral load. We hypothesized that CT values would be higher, and thus the viral loads at the time of diagnosis would be lower, in individuals who were infected with the virus but remained asymptomatic throughout the course of the infection. We collected the N1 and N2 target gene CT values from 1633 SARS-CoV-2 positive RT-qPCR tests of individuals sampled between August 7, 2020, and March 18, 2021, at the BU Clinical Testing Laboratory. We matched this data with symptom reporting data from our clinical team. We found that asymptomatic patients had CT values significantly higher than symptomatic individuals on the day of diagnosis. Symptoms were followed by the clinical team for 10 days post the first positive test. Within the entire population, 78.1% experienced at least one symptom during surveillance by the clinical team (n = 1276/1633). Of those experiencing symptoms, the most common symptoms were nasal congestion (73%, n = 932/1276), cough (60.0%, n = 761/1276), fatigue (59.0%, n = 753/1276), and sore throat (53.1%, n = 678/1276). The least common symptoms were diarrhea (12.5%, n = 160/1276), dyspnea on exertion (DOE) (6.9%, n = 88/1276), foot or skin changes (including rash) (4.2%, n = 53/1276), and vomiting (2.1%, n = 27/1276). Presymptomatic individuals, those who were not symptomatic on the day of diagnosis but became symptomatic over the following 10 days, had CT values higher for both N1 (median = 27.1, IQR 20.2-32.9) and N2 (median = 26.6, IQR 20.1-32.8) than the symptomatic group N1 (median = 21.8, IQR 17.2-29.4) and N2 (median = 21.4, IQR 17.3-28.9) but lower than the asymptomatic group N1 (median = 29.9, IQR 23.6-35.5) and N2 (median = 30.0, IQR 23.1-35.7). This study supports the hypothesis that viral load in the anterior nares on the day of diagnosis is a measure of disease intensity at that time.
在我们基于大学的高通量筛选计划中，我们每周使用 RT-qPCR 测试我们社区的所有成员。RT-qPCR 循环阈值 (CT) 值与样品中的病毒 RNA 量成反比，是病毒载量的代表。我们假设，在感染病毒但在整个感染过程中一直无症状的个体中，CT 值会更高，因此诊断时的病毒载量会更低。我们从 2020 年 8 月 7 日至 2021 年 3 月 18 日在 BU 临床检测实验室对 1633 例 SARS-CoV-2 阳性 RT-qPCR 检测的 N1 和 N2 靶基因 CT 值进行了收集。我们将此数据与我们临床团队的症状报告数据进行了匹配。我们发现无症状患者在诊断日的 CT 值明显高于有症状的个体。症状由临床团队在首次阳性检测后的 10 天内进行跟踪。在整个人群中，78.1%（n=1276/1633）在临床团队的监测期间至少经历过一种症状。在有症状的人群中，最常见的症状是鼻塞（73%，n=932/1276）、咳嗽（60.0%，n=761/1276）、疲劳（59.0%，n=753/1276）和喉咙痛（53.1%，n=678/1276）。最不常见的症状是腹泻（12.5%，n=160/1276）、用力呼吸困难（DOE）（6.9%，n=88/1276）、足部或皮肤变化（包括皮疹）（4.2%，n=53/1276）和呕吐（2.1%，n=27/1276）。前驱症状患者，即在诊断日无症状但在接下来的 10 天内出现症状的患者，其 N1（中位数=27.1，IQR 20.2-32.9）和 N2（中位数=26.6，IQR 20.1-32.8）的 CT 值均高于无症状组的 N1（中位数=21.8，IQR 17.2-29.4）和 N2（中位数=21.4，IQR 17.3-28.9），但低于无症状组的 N1（中位数=29.9，IQR 23.6-35.5）和 N2（中位数=30.0，IQR 23.1-35.7）。这项研究支持这样一种假设，即在诊断日鼻前的病毒载量是当时疾病严重程度的衡量标准。
