Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2) has been identified as the causative agent for causing the clinical syndrome of COVID -19. Accurate detection of SARS-CoV-2 infection is not only important for management of infected individuals but also to break the chain of transmission. South Africa is the current epicenter of SARS-CoV-2 infection in Africa. To optimize the diagnostic algorithm for SARS-CoV-2 in the South African setting, the study aims to evaluate the diagnostic performance of the EUROIMMUN Anti-SARS-CoV-2 assays. This study reported the performance of EUROIMMUN enzyme-linked immunosorbent assay (ELISA) for semi-quantitative detection of IgA and IgG antibodies in serum and plasma samples targeting the recombinant S1 domain of the SARS-CoV-2 spike protein as antigen. Samples were collected from 391 individuals who had tested positive for SARS-CoV-2 and 139 SARS CoV-2 negative controls. Samples were stratified by number of days’ post-PCR diagnosis and symptoms. The sensitivity of EUROIMMUN IgG was 64.1% (95% CI: 59.1–69.0%) and 74.3% (95% CI: 69.6–78.6%) for IgA and the specificity was lower for IgA [84.2% (95% CI: 77–89.2%)] than IgG [95.2% (95% CI: 90.8–98.4%)]. The EUROIMMUN Anti-SARS-CoV-2 ELISA Assay sensitivity was higher for IgA but low for IgG and improved for both assays in symptomatic individuals and at later timepoints post PCR diagnosis.
In late December 2019, pneumonia cases of unknown origin were reported in Wuhan, China. This virus was named SARS-CoV2 and the clinical syndrome was named coronavirus disease 19 (COVID-19). South Africa, despite strict and early lockdown has the highest infection rate in Africa. A key component of South Africa’s response to SARSCoV2 was the rapid scale-up of diagnostic testing. The Abbott SARS-CoV2 assay detects IgG antibodies against the Nucleocapsid (N) protein of the SARS-CoV2 virus. This study undertook to validate and evaluate performance criteria of the Abbott assay and to establish whether this assay would show clinical utility in our population. Positive patients (n = 391) and negative controls (n = 139) were included. The Architect-i and Alinity-i systems were analyzers that were used to perform the SARS-CoV-2 IgG assay. In-house ELISA was incorporated into the study as a confirmatory serology test. A total of number of 530 participants was tested, 87% were symptomatic with infection and 13% were asymptomatic. When compared to RT-qPCR, the sensitivity of Architect and Alinity SARS-CoV2 assays was 69.5% and 64.8%, respectively. Specificity for Architect and Alinity assays was 95% and 90.3%, respectively. The Abbott assay was also compared to in house ELISA assay, with sensitivity for the Architect and Alinity assays of 94.7% and 92.5%, respectively. Specificity for Abbott Alinity assays was 91.7% higher than Abbott Architect 88.1%. Based on the current findings testing of IgG after 14 days is recommended in South Africa and supports other studies performed around the world.
Background: Serology testing is an important ancillary diagnostic to the reverse transcriptase polymerase chain reaction (RT-PCR) test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We aimed to evaluate the performance of the Roche Elecsys™ chemiluminescent immunoassay (Rotkreuz, Switzerland), that detects antibodies against the SARS-CoV-2 nucleocapsid antigen, at an academic laboratory in South Africa.Methods: Serum samples were collected from 312 donors with confirmed positive SARS-CoV-2 RT-PCR tests, with approval from a large university’s human research ethics committee. Negative controls included samples stored prior to December 2019 and from patients who tested negative for SARS-CoV-2 on RT-PCR and were confirmed negative using multiple serology methods (n = 124). Samples were stored at –80 °C and analysed on a Roche cobas™ 602 autoanalyser.Results: Compared with RT-PCR, our evaluation revealed a specificity of 100% and overall sensitivity of 65.1%. The sensitivity in individuals 14 days’ post-diagnosis was 72.6%, with the highest sensitivity 31–50 days’ post-diagnosis at 88.6%. Results were also compared with in-house serology tests that showed high agreement in majority of categories.Conclusions: The sensitivity at all-time points post-diagnosis was lower than reported in other studies, but sensitivity in appropriate cohorts approached 90% with a high specificity. The lower sensitivity at earlier time points or in individuals without symptomatology may indicate failure to produce antibodies, which was further supported by the comparison against in-house serology tests.
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