Department of Laboratory Medicine, University Hospital of Padova, Padova, Italy.
Department of Medicine-DIMED, Medical School, University of Padova, Padova, Italy.
Clin Chem Lab Med. 2020 Jun 25;58(7):1081-1088. doi: 10.1515/cclm-2020-0443.
Background Coronavirus disease 2019, abbreviated to COVID-19, represents an emerging health threat worldwide as, after initial reports in China, it has continued to spread rapidly. The clinical spectrum of the disease varies from mild to severe acute respiratory distress syndrome (ARDS). Moreover, many patients can be asymptomatic, thus increasing the uncertainty of the diagnostic work-up. Laboratory tests play a pivotal role in the diagnosis and management of COVID-19, the current gold standard being real-time reverse transcription polymerase chain reaction (rRT-PCR) on respiratory tract specimens. However, the diagnostic accuracy of rRT-PCR depends on many pre-analytical and analytical variables. The measurement of specific COVID-19 antibodies (both IgG and IgM) should serve as an additional, non-invasive tool for disease detection and management. Methods The imprecision of the MAGLUMI™ 2000 Plus 2019-nCov IgM and IgG assays (Snibe, Shenzhen, China) was assessed by adopting the Clinical and Laboratory Standards Institute (CLSI) EP15-A3 protocol. Linearity of dilution and recovery was evaluated by means of mixes of high-level pools and low-level pools of serum samples. Immunoglobulin time kinetics were evaluated using a series of serum samples, repeatedly collected from COVID-19-positive patients at different times, from <5 days up to 26-30 days. Results Findings at the analytical validation of the assay carried out according to the CLSI EP15-A3 guideline demonstrated that imprecision and repeatability were acceptable (repeatability was <4% and <6% for IgM and IgG, respectively, whilst intermediate imprecision was <6%). In addition, results of dilution and recovery studies were satisfactory. The kinetics of COVID-19 antibodies confirmed previously reported findings, showing a rapid increase of both IgM and IgG after 6-7 days from the symptom onset. IgG had 100% sensitivity on day 12, whilst 88% was the higher positive rate achieved for IgM after the same time interval. Conclusions The findings of this study demonstrate the validity of the MAGLUMI 2000 Plus CLIA assay for the measurement of specific IgM and IgG in sera of COVID-19 patients, and for obtaining valuable data on the kinetics of both (IgM and IgG) COVID-19 antibodies. These data represent a pre-requisite for the appropriate utilization of specific antibodies for the diagnosis and management of COVID-19 patients.
2019 年冠状病毒病，简称 COVID-19，是全球范围内新出现的健康威胁，最初在中国报告后，该疾病继续迅速传播。该疾病的临床谱从轻度到严重急性呼吸窘迫综合征（ARDS）不等。此外，许多患者可能无症状，从而增加了诊断工作的不确定性。实验室检测在 COVID-19 的诊断和管理中起着关键作用，目前的金标准是呼吸道标本的实时逆转录聚合酶链反应（rRT-PCR）。然而，rRT-PCR 的诊断准确性取决于许多分析前和分析变量。测量特定的 COVID-19 抗体（IgG 和 IgM）都应作为疾病检测和管理的一种额外的、非侵入性工具。
采用临床和实验室标准协会（CLSI）EP15-A3 方案评估 MAGLUMI™2000 Plus 2019-nCov IgM 和 IgG 检测的不精密度。通过高、低水平血清样本混合液评估线性稀释和回收。使用一系列从不同时间采集的 COVID-19 阳性患者的血清样本评估免疫球蛋白时间动力学，从<5 天到 26-30 天不等。
根据 CLSI EP15-A3 指南进行的检测分析验证结果表明，不精密度和重复性是可以接受的（IgM 和 IgG 的重复性分别<4%和<6%，而中间不精密度<6%）。此外，稀释和回收研究的结果令人满意。COVID-19 抗体的动力学证实了之前的研究结果，表明从症状出现后 6-7 天，IgM 和 IgG 迅速增加。在第 12 天，IgG 的敏感性达到 100%，而在同一时间间隔后，IgM 的阳性率达到 88%。
本研究结果表明，MAGLUMI 2000 Plus CLIA 检测可用于测量 COVID-19 患者血清中的特异性 IgM 和 IgG，并可获得关于 COVID-19 抗体（IgM 和 IgG）动力学的有价值数据。这些数据是为 COVID-19 患者的诊断和管理适当利用特异性抗体提供了前提。
