key: cord-0798831-8l20ssjl authors: Kim, Jae Kyung; Ryu, Sook Won; Kim, Jae Soo; Jung, Bo Kyeung title: Performance evaluation of four rapid antibody tests for the detection of severe acute respiratory syndrome coronavirus 2 date: 2022-04-21 journal: J Clin Lab Anal DOI: 10.1002/jcla.24374 sha: 3be3324be2e9a90044d1997c26cccfa1c2704ac5 doc_id: 798831 cord_uid: 8l20ssjl BACKGROUND: The prompt detection of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is important in the therapeutic management of infected patients. Rapid diagnostic tests are widely used for this purpose. This study aimed to evaluate the clinical performance of four SARS‐CoV‐2 immunoglobulin IgG/IgM rapid diagnostic tests in the detection of SARS‐CoV‐2. METHODS: Nasopharyngeal and oropharyngeal swabs and/or sputum were collected from 30 patients infected with SARS‐CoV‐2 and 30 healthy volunteers. All specimens were tested using four SARS‐CoV‐2 IgG/IgM rapid diagnostic tests and real‐time polymerase chain reaction. We assessed the clinical sensitivity and specificity of the tests. RESULTS: The clinical sensitivity of FREND™, SsmarTest™, BIOCREDIT™, and IVDLAB™ was 96.67%, 100.00%, 100.00%, and 96.67%, respectively, compared to real‐time polymerase chain reaction. The clinical specificity was 96.67%, 100.00%, 86.67%, and 96.67%, respectively. CONCLUSION: These findings could expedite the detection of SARS‐CoV‐2 and thus reduce the risk of further transmission of the virus. test, is now considered the gold standard for SARS-CoV-2 detection in Korea despite the potential of false negatives. 5, 6 Additional limitations of qRT-PCR are that it takes several hours to provide results, and it requires well-trained personnel and expensive equipment to perform. Rapid diagnostic tests (RDTs), which use a capillary technique, are widely used for the timely detection of various pathogens. 7 An RDT is a simple procedure that requires a very small sample size and provides results within 15 min. The several commercially developed RDTs that have been approved for emergency use in the detection of SARS-CoV-2 (http://www.fda. gov/medic al-devic es/coron aviru s-disea se-2019-covid -19-emerg ency-use-autho rizat ions-medic al-devic es/eua-autho rized -serol ogytest-perfo rmance) are developed to detect SARS-CoV-2 antigens or SARS-CoV-2 immunoglobulin IgG/IgM antibodies. This study aimed to determine the clinical performance of four SARS-CoV-2 immunoglobulin IgG/IgM RDTs used to detect SARS-CoV-2 and compare the results with qRT-PCR data. Between February 28th and May 6th, 2020, nasopharynx swabs, oropharyngeal swabs, and sputum were collected from 30 patients infected with SARS-CoV-2 and 30 healthy volunteers. All collected samples were stored at −80°C. All specimens were tested for SARS-CoV-2 using four SARS- The study protocol was approved by Dankook University Institutional Review Board (IRB approval number 2020-11-013). The study was conducted in conformance with the principles of the Declaration of Helsinki. Patient consent was waived because this study used statistics from tests conducted by medical institutions for diagnosis and did not use the patients' personal information. The kit components and specimens were equilibrated to room temperature before testing. The test device was removed from the foil pouch and placed on a clean, dry, and level surface. Then 10 µl of serum or plasma, or 20 µl of whole blood, was added to the sample well (S) of the device using a capillary tube or disposable dropper. Three drops of assay buffer were then added to the S. The results were provided within 10-15 min. The tubes and sealed pouches from the kit were thawed to room temperature for 15-30 min before the testing procedure. The sample ID was recorded on the cartridge in the designated area. A 35 µl sample was added to a sample dilution tube and mixed well. This sample was pipetted into the sample inlet on the cartridge using a calibrated micropipette with a fresh tip. The "Test" button was pressed on the "Main" screen of the FREND™ System. The system moved to the Patient ID screen automatically. The Patient ID was entered, and the "Enter" key was pressed to begin the test. The cartridge was inserted into the cartridge slot using the cartridge arrows as a guide. When the reaction in the cartridge was complete, the FREND™ System automatically began the reading process. When the measurements were completed, the cartridge was automatically expelled, and the results were displayed. The specimens and the test device were equilibrated to room temperature before testing (15-30 min). The sealed pouch was opened, and the device was placed on a clean, dry, and level surface. Using a micropipette or capillary microtip, 10 µl of serum, plasma, or whole blood was added to the sample well. Approximately two to three drops (80-120 µl) of dilution solution were added to the sample wells. The results were provided within 10 min. The personal identification number of the sample was written on the device. Then, using the enclosed syringe, 10 µl of the sample was carefully dispensed into the device to avoid overfilling it. When the sample pad absorbed the entire sample, 20 µl of the enclosed running solution was added. The results were obtained within 15-20 min. Finally, interpretation of the results from the four RDTs was carried out. The FREND™ System detects SARS-CoV-2 IgG/IgM using a fluorescence immunoassay. The cut-off index (COI) is determined quantitatively by testing the specimens that were collected 8 days from The In total, 60 specimens collected between February 28th and May 6th, 2020, were tested for SARS-CoV-2 infection using four SARS- positive by these tests. The results were confirmed by qRT-PCR analysis ( Table 2) . The IgG and IgM positivity rate detected using the BIOCREDIT™ test was 50.0% (30/60) and 53.3% (32/60), respectively ( CoV-2, and the S protein is highly immunogenic. 9 The receptor-binding domain (RBD) of the S protein combines with angiotensin-converting enzyme-2 receptors in the lower bronchial system and lung and mediates infection. 10 The neutralizing antibody blocks this pathway, preventing virus infection in the early phase. 9 Therefore, candidate vaccines for SARS-CoV-2 adopt the RBD of the S protein as a stimulant to the host immune system. Indeed, a vaccine with an RBD of the S protein of SARS-CoV could elicit a neutralizing antibody response and protective activity in vaccinated animals. 11 However, to date, no commercially available serological test has been used to detect neutralizing antibodies, regardless of the antigenic target. 12 Hence, the positive results of an RDT kit should not be used to indicate "immunity passports" because immunity-based licenses can only be introduced if serology testing for the neutralizing antibody is accurate. 13 According to this study, IgM antibodies are present 6 days after infection. This finding supports those of previous studies. 14, 15 Regarding IgG, one study revealed that 40% of asymptomatic individuals and 12.9% of symptomatic individuals were negative for We expect that this study will provide information that can be used to safeguard public health, reduce the incidence of coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2, and provide information that can be used to treat patients. Thank Dankook University Hospital for specimen collection. The authors declare that there are no conflicts of interest. All authors approved the final article. JS Kim and JK Kim made substantial contributions to the conception and design of the study. SW Ryu and BK Jung made substantial contributions to data acquisition and analysis. All authors agree to be accountable for all aspects of the study and ensure that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Patient consent was waived for this study. 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