Background: Serologic assays for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) have roles in seroepidemiology, convalescent plasma-testing, antibody durability and vaccine studies. Currently, SARS-CoV-2 serology is performed using serum/plasma collected by venepuncture. Dried bloodspot (DBS) testing offers significant advantages; as it is minimally invasive, avoids venepuncture with specimens being mailed to the laboratory.

Methods: A pathway utilising a newborn screening laboratory infrastructure was developed using an Enzyme-Linked Immunosorbent assay (ELISA) to detect IgG antibodies against the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein in DBS specimens. Paired plasma and DBS specimens from SARS-CoV-2 antibody positive and negative subjects and PCR positive subjects were tested. DBS specimen stability, effect of blood volume and punch location were also evaluated.

Results: DBS from antibody-negative (n=85) and positive (n=35) subjects and PCR positive subjects (n=11) had a mean (SD; range) optical density (OD) of 0.14 (0.046; 0.03-0.27), 0.98 (0.41; 0.31-1.64) and 1.12 (0.37; 0.49-1.54), respectively. An action value OD >0.28 correctly assigned all cases. The weighted Deming regression for comparison of the DBS and the plasma assay yielded: y=0.004041+1.005x, r=0.991, Sy/x 0.171, n=82. Extraction efficiency of antibodies from DBS was >99%. DBS were stable for at least 28 days at ambient room temperature and humidity.

Conclusions: SARS-CoV-2 IgG RBD antibodies can be reliably detected in DBS. DBS serological testing offers lower costs than either point of care or serum/plasma assays that require patient travel, phlebotomy and hospital/clinic resources; the development of a DBS assay may be particularly important for resource poor settings.

背景：严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 的血清学检测在血清流行病学、恢复期血浆检测、抗体耐久性和疫苗研究中发挥着重要作用。目前，SARS-CoV-2 血清学检查是使用静脉穿刺收集的血清/血浆进行的。干血斑 (DBS) 检测具有显着的优势；由于它是微创的，因此可以避免静脉穿刺并将标本邮寄到实验室。

方法：利用酶联免疫吸附测定 (ELISA) 开发了一条利用新生儿筛查实验室基础设施的途径，以检测 DBS 样本中针对 SARS-CoV-2 刺突蛋白受体结合域 (RBD) 的 IgG 抗体。对来自 SARS-CoV-2 抗体阳性和阴性受试者以及 PCR 阳性受试者的配对血浆和 DBS 样本进行了测试。还评估了 DBS 样本的稳定性、血量和打孔位置的影响。

结果：抗体阴性 (n=85) 和阳性 (n=35) 受试者以及 PCR 阳性受试者 (n=11) 的 DBS 平均（SD；范围）光密度 (OD) 为 0.14 (0.046；0.03-0.27) ）、0.98（0.41；0.31-1.64）和 1.12（0.37；0.49-1.54）。操作值 OD >0.28 正确分配所有情况。用于比较 DBS 和血浆测定的加权戴明回归得出：y=0.004041+1.005x，r=0.991，Sy/x 0.171，n=82。 DBS 中抗体的提取效率 >99%。 DBS 在环境室温和湿度下稳定至少 28 天。

结论：在 DBS 中可以可靠地检测到 SARS-CoV-2 IgG RBD 抗体。 DBS 血清学检测的成本低于需要患者出行、抽血和医院/诊所资源的护理点或血清/血浆检测； DBS 检测的开发对于资源匮乏的环境可能特别重要。