Diagnostic tests for direct pathogen detection have been instrumental to contain the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) pandemic. Automated, quantitative, laboratory-based nucleocapsid antigen (Ag) tests for SARS-CoV-2 have been launched alongside nucleic acid-based test systems and point-of-care (POC) lateral-flow Ag tests. Here, we evaluated four commercial Ag tests on automated platforms for the detection of different sublineages of the SARS-CoV-2 Omicron variant of concern (VoC) (B.1.1.529) in comparison with “non-Omicron” VoCs. A total of 203 Omicron PCR-positive respiratory swabs (53 BA.1, 48 BA.2, 23 BQ.1, 39 XBB.1.5 and 40 other subvariants) from the period February to March 2022 and from March 2023 were examined. In addition, tissue culture-expanded clinical isolates of Delta (B.1.617.2), Omicron-BA.1, -BF.7, -BN.1 and -BQ.1 were studied. These results were compared to previously reported data from 107 clinical “non-Omicron” samples from the end of the second pandemic wave (February to March 2021) as well as cell culture-derived samples of wildtype (wt) EU-1 (B.1.177), Alpha VoC (B.1.1.7) and Beta VoC (B.1.351)). All four commercial Ag tests were able to detect at least 90.9% of Omicron-containing samples with high viral loads (Ct < 25). The rates of true-positive test results for BA.1/BA.2-positive samples with intermediate viral loads (Ct 25–30) ranged between 6.7% and 100.0%, while they dropped to 0 to 15.4% for samples with low Ct values (> 30). This heterogeneity was reflected also by the tests’ 50%-limit of detection (LoD50) values ranging from 44,444 to 1,866,900 Geq/ml. Respiratory samples containing Omicron-BQ.1/XBB.1.5 or other Omicron subvariants that emerged in 2023 were detected with enormous heterogeneity (0 to 100%) for the intermediate and low viral load ranges with LoD50 values between 23,019 and 1,152,048 Geq/ml. In contrast, detection of “non-Omicron” samples was more sensitive, scoring positive in 35 to 100% for the intermediate and 1.3 to 32.9% of cases for the low viral loads, respectively, corresponding to LoD50 values ranging from 6181 to 749,792 Geq/ml. All four assays detected cell culture-expanded VoCs Alpha, Beta, Delta and Omicron subvariants carrying up to six amino acid mutations in the nucleocapsid protein with sensitivities comparable to the non-VoC EU-1. Overall, automated quantitative SARS-CoV-2 Ag assays are not more sensitive than standard rapid antigen tests used in POC settings and show a high heterogeneity in performance for VoC recognition. The best of these automated Ag tests may have the potential to complement nucleic acid-based assays for SARS-CoV-2 diagnostics in settings not primarily focused on the protection of vulnerable groups. In light of the constant emergence of new Omicron subvariants and recombinants, most recently the XBB lineage, these tests’ performance must be regularly re-evaluated, especially when new VoCs carry mutations in the nucleocapsid protein or immunological and clinical parameters change.

直接病原体检测的诊断测试有助于遏制严重急性呼吸综合征冠状病毒 2 型 (SARS-CoV-2) 的流行。基于实验室的 SARS-CoV-2 自动化、定量核衣壳抗原 (Ag) 检测已与基于核酸的检测系统和即时 (POC) 侧流 Ag 检测一起启动。在这里，我们评估了自动化平台上的四种商业 Ag 测试，用于检测 SARS-CoV-2 Omicron 关注变体 (VoC) (B.1.1.529) 的不同亚系，并与“非 Omicron”VoC 进行比较。2022 年 2 月至 3 月以及 2023 年 3 月期间总共检查了 203 份 Omicron PCR 阳性呼吸道拭子（53 份 BA.1、48 份 BA.2、23 份 BQ.1、39 份 XBB.1.5 和 40 份其他亚变体）。此外，还研究了 Delta (B.1.617.2)、Omicron-BA.1、-BF.7、-BN.1 和 -BQ.1 的组织培养扩增临床分离株。这些结果与之前报道的第二波大流行结束时（2021 年 2 月至 3 月）的 107 个临床“非 Omicron”样本以及野生型 (wt) EU-1 (B. 1.177)、Alpha VoC (B.1.1.7) 和 Beta VoC (B.1.351))。所有四项商业 Ag 检测均能够检测出至少 90.9% 的含有 Omicron 的高病毒载量样本 (Ct < 25)。病毒载量中等（Ct 25-30）的 BA.1/BA.2 阳性样本的真阳性检测结果率在 6.7% 至 100.0% 之间，而低 Ct 样本的真阳性检测结果率则降至 0 至 15.4%值（> 30）。测试的 50% 检测限 (LoD50) 值范围为 44,444 至 1,866,900 Geq/ml，也反映了这种异质性。检测到的含有 Omicron-BQ.1/XBB.1.5 或其他 2023 年出现的 Omicron 亚变体的呼吸道样本在中低病毒载量范围内具有巨大的异质性（0 至 100%），LoD50 值在 23,019 至 1,152,048 Geq/ml 之间。相比之下，“非 Omicron”样本的检测更为灵敏，中间病毒载量病例的阳性率为 35% 至 100%，低病毒载量病例的阳性率为 1.3% 至 32.9%，对应的 LoD50 值范围为 6181 至 749,792 Geq /毫升。所有四种检测均检测到细胞培养扩增的 VoC Alpha、Beta、Delta 和 Omicron 亚变体，其核衣壳蛋白中携带多达 6 个氨基酸突变，其灵敏度与非 VoC EU-1 相当。总体而言，自动化定量 SARS-CoV-2 Ag 检测并不比 POC 环境中使用的标准快速抗原检测更敏感，并且在 VoC 识别性能方面表现出高度异质性。在不主要关注保护弱势群体的环境中，这些自动化 Ag 测试中最好的可能有可能补充基于核酸的 SARS-CoV-2 诊断检测方法。鉴于新的 Omicron 亚变体和重组体（最近的 XBB 谱系）的不断出现，必须定期重新评估这些测试的性能，