Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.
Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.
Clin Chem Lab Med. 2022 Feb 16;60(5):771-777. doi: 10.1515/cclm-2021-1142. Print 2022 Apr 26.
Widespread SARS-CoV-2 testing is invaluable for identifying asymptomatic/pre-symptomatic individuals. There remains a technological gap for highly reliable, easy, and quick SARS-CoV-2 diagnostic tests suitable for frequent mass testing. Compared to nasopharyngeal (NP) swab-based tests, saliva-based methods are attractive due to easier and safer sampling. Current saliva-based SARS-CoV-2 rapid antigen tests (RATs) are hindered by limited analytical sensitivity. Here, we report one of the first ultrasensitive, saliva-based SARS-CoV-2 antigen assays with an analytical sensitivity of <0.32 pg/mL, corresponding to four viral RNA copies/µL, which is comparable to that of PCR-based tests.
Using the novel electrochemiluminescence (ECL)-based immunoassay, we measured the SARS-CoV-2 nucleocapsid (N) antigen concentration in 105 salivas, obtained from non-COVID-19 and COVID-19 patients. We then verified the results with a second, independent cohort of 689 patients (3.8% SARS-CoV-2 positivity rate). We also compared our method with a widely used point-of-care rapid test.
In the first cohort, at 100% specificity, the sensitivity was 92%. Our assay correctly identified samples with viral loads up to 35 CT cycles by saliva-based PCR. Paired NP swab-based PCR results were obtained for 86 cases. Our assay showed high concordance with saliva-based and NP swab-based PCR in samples with negative (<0.32 pg/mL) and strongly positive (>2 pg/mL) N antigen concentrations. In the second cohort, at 100% specificity, sensitivity was also 92%. Our assay is about 700-fold more sensitive than the Abbott Panbio Rapid Test.
We demonstrated the ultrasensitivity and specificity assay and its concordance with PCR. This novel assay is especially valuable when compliance to frequent swabbing may be problematic.
广泛的 SARS-CoV-2 检测对于识别无症状/有症状前个体非常有价值。目前仍存在技术差距，需要开发高度可靠、简便、快速的 SARS-CoV-2 诊断检测方法，以适用于频繁的大规模检测。与鼻咽（NP）拭子检测相比，唾液检测方法具有采样更容易、更安全的优势。目前的唾液 SARS-CoV-2 快速抗原检测（RAT）存在分析灵敏度有限的问题。在此，我们报告了首批超灵敏唾液 SARS-CoV-2 抗原检测方法之一，其分析灵敏度<0.32 pg/mL，相当于 4 个病毒 RNA 拷贝/µL，与基于 PCR 的检测方法相当。
使用新型电化学发光（ECL）基于免疫测定法，我们测量了来自非 COVID-19 和 COVID-19 患者的 105 份唾液中的 SARS-CoV-2 核衣壳（N）抗原浓度。然后，我们使用第二个独立的 689 例患者队列（3.8%的 SARS-CoV-2 阳性率）对结果进行了验证。我们还将我们的方法与一种广泛使用的即时检测快速检测方法进行了比较。
在第一个队列中，特异性为 100%时，敏感性为 92%。我们的检测方法可正确识别病毒载量高达 35 CT 循环的样本。对于 86 例样本，获得了基于 NP 拭子的配对 PCR 结果。在阴性（<0.32 pg/mL）和强阳性（>2 pg/mL）N 抗原浓度的样本中，我们的检测方法与基于唾液和 NP 拭子的 PCR 具有高度一致性。在第二个队列中，特异性为 100%时，敏感性也为 92%。我们的检测方法比 Abbott Panbio Rapid Test 灵敏约 700 倍。
我们证明了该超灵敏和特异性检测方法及其与 PCR 的一致性。当频繁拭子采样可能存在问题时，该新型检测方法特别有价值。
