Department of Microbiology, Jahangirnagar University, Dhaka, Bangladesh.
Department of Research and Development, Gonoshasthaya-RNA Molecular Diagnostic & Research Center, Dhaka, Bangladesh.
Expert Rev Anti Infect Ther. 2022 Mar;20(3):473-481. doi: 10.1080/14787210.2021.1976144. Epub 2021 Sep 11.
Rapid increase in COVID-19 suspected cases has rendered disease diagnosis challenging, mainly depending upon RT-qPCR. Reliable, rapid, and cost-effective diagnostic assays that complement RT-qPCR should be introduced after thoroughly evaluating their performance upon various disease phases, viral load, and sample storage conditions.
We investigated the correlation of cycle threshold (Ct) value, which implies the viral load and infection phase, and the storage condition of the clinical specimen with the diagnosis of SARS-CoV-2 through our newly developed in-house rapid enzyme-linked immunosorbent assay (ELISA) system.
Naso-oropharyngeal samples of 339 COVID-19 suspected cases were collected and evaluated through RT-qPCR that were stored up to 30 days in different conditions (i.e. -80°C, -20°C and initially at 4°C followed by -80°C). The clinical specimens were evaluated with our in-house ELISA system after finalizing the assay method through checkerboard assay and minimizing the signal/noise ratio.
The ELISA system showed the highest sensitivity (92.9%) for samples with Ct ≤30 and preserving at -80°C temperature. The sensitivity reduced proportionally with increasing Ct value and preserving temperature. However, the specificity ranged between 98.3% and 100%.
The results indicate the necessity of early infection phase diagnosis and lower temperature preservation of samples to perform rapid antigen ELISA tests.
COVID-19 疑似病例的迅速增加使得疾病诊断变得具有挑战性，主要依赖于 RT-qPCR。应该引入可靠、快速且具有成本效益的诊断检测方法，以补充 RT-qPCR，在各种疾病阶段、病毒载量和样本储存条件下对其性能进行彻底评估后再进行引入。
我们通过新开发的内部快速酶联免疫吸附测定（ELISA）系统，研究了循环阈值（Ct）值与病毒载量和感染阶段以及临床标本储存条件与 SARS-CoV-2 诊断之间的相关性。
收集了 339 例 COVID-19 疑似病例的鼻咽或口咽样本，并通过 RT-qPCR 进行评估，这些样本在不同条件下（即-80°C、-20°C 和最初在 4°C 下，然后在-80°C 下）储存长达 30 天。在通过棋盘试验确定检测方法并最小化信号/噪声比后，使用内部 ELISA 系统对临床标本进行评估。
对于 Ct 值≤30 且保存在-80°C 温度下的样本，ELISA 系统显示出最高的灵敏度（92.9%）。灵敏度随着 Ct 值和保存温度的增加而成比例降低。然而，特异性在 98.3%到 100%之间。
这些结果表明，需要早期感染阶段的诊断和样本的低温保存，以便进行快速抗原 ELISA 检测。
