Instituto de Ciencia Animal, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia, Chile.
Laboratorio de Biología Molecular, Hospital Base de Valdivia (HBV), Valdivia, Chile.
PLoS One. 2023 Feb 6;18(2):e0270388. doi: 10.1371/journal.pone.0270388. eCollection 2023.
The main objective of this study was to estimate the performance, under local epidemiological conditions, of two in-house ELISA assays for the combined detection of anti-SARS-CoV-2 IgA, IgM, and IgG immunoglobulins. A total of 94 serum samples were used for the assessment, where 44 corresponded to sera collected before the pandemic (free of SARS-CoV-2 antibodies), and 50 sera were collected from confirmed COVID-19 patients admitted to the main public hospital in the city of Valdivia, southern Chile. The Nucleocapsid (Np) and the receptor-binding domain (RBD) proteins were separately used as antigens (Np and RBD ELISA, respectively) to assess their diagnostic performance. A receiver operating characteristic (ROC) analysis was performed to estimate the optical density (OD) cut-off that maximized the sensitivity (Se) and specificity (Sp) of the ELISA assays. Np ELISA had a mean Se of 94% (95% CI = 83.5-98.8%) and a mean Sp of 100% (95% CI = 92.0-100%), with an OD 450 nm positive cut-off value of 0.88. On the other hand, RBD ELISA presented a mean Se of 96% (95% CI = 86.3-99.5%) and a mean Sp of 90% (95% CI = 78.3-97.5%), with an OD 450 nm positive cut off value of 0.996. Non-significant differences were observed between the Se distributions of Np and RBD ELISAs, but the latter presented a significant lower Sp than Np ELISA. In parallel, collected sera were also analyzed using a commercial lateral flow chromatographic immunoassay (LFCI), to compare the performance of the in-house ELISA assays against a commercial test. The LFCI had a mean sensitivity of 94% (95% CI = 87.4-100%) and a mean specificity of 100% (95% CI = 100-100%). When compared to Np ELISA, non-significant differences were observed on the performance distributions. Conversely, RBD ELISA had a significant lower Sp than the LFCI. Although, Np ELISA presented a similar performance to the commercial test, this was 2.5 times cheaper than the LFCI assay (labor cost not considered). Thus, the in-house Np ELISA could be a suitable alternative tool, in resource limited environments, for the surveillance of SARS-CoV-2 infection, supporting further epidemiological studies.
本研究的主要目的是评估两种用于联合检测抗 SARS-CoV-2 IgA、IgM 和 IgG 免疫球蛋白的内部 ELISA 检测方法在当地流行条件下的性能。共使用了 94 份血清样本进行评估，其中 44 份来自大流行前采集的血清（无 SARS-CoV-2 抗体），50 份来自智利南部瓦尔迪维亚市主要公立医院收治的确诊 COVID-19 患者。核衣壳（Np）和受体结合域（RBD）蛋白分别用作抗原（分别为 Np 和 RBD ELISA），以评估它们的诊断性能。进行了接收者操作特征（ROC）分析，以估计最大灵敏度（Se）和特异性（Sp）的光密度（OD）截止值。Np ELISA 的平均 Se 为 94%（95%CI=83.5-98.8%），平均 Sp 为 100%（95%CI=92.0-100%），OD450nm 阳性截断值为 0.88。另一方面，RBD ELISA 的平均 Se 为 96%（95%CI=86.3-99.5%），平均 Sp 为 90%（95%CI=78.3-97.5%），OD450nm 阳性截断值为 0.996。Np 和 RBD ELISA 的 Se 分布无显著差异，但后者的 Sp 明显低于 Np ELISA。同时，还使用商业侧向流动色谱免疫测定法（LFCI）分析收集的血清，以比较内部 ELISA 检测方法与商业检测的性能。LFCI 的平均灵敏度为 94%（95%CI=87.4-100%），平均特异性为 100%（95%CI=100-100%）。与 Np ELISA 相比，性能分布无显著差异。相反，RBD ELISA 的 Sp 明显低于 LFCI。虽然 Np ELISA 的性能与商业检测相似，但价格便宜 2.5 倍（不考虑劳动力成本）。因此，内部 Np ELISA 可能是资源有限环境中 SARS-CoV-2 感染监测的合适替代工具，支持进一步的流行病学研究。
