Evaluation of Three Commercial SARS-CoV-2 Serologic Assays and Their Performance in Two-Test Algorithms

Abstract

Background. Sensitive and specific SARS-CoV-2 serologic assays are needed to inform diagnostic, therapeutic, and public health decision-making. We evaluated three commercial serologic assays as stand-alone tests and as components of two-test algorithms. Methods. Two nucleocapsid (Abbott IgG and Roche total antibody) and one spike-protein (DiaSorin IgG) antibody tests were included. We assessed sensitivity using 128 serum samples from symptomatic PCR-confirmed COVID-19-infected patients, and specificity using 1204 samples submitted for routine serologies prior to COVID-19's emergence, plus 64 pandemic-era samples from SARS-CoV-2 PCR-negative patients with respiratory symptoms. Assays were evaluated as stand-alone tests and as components of a two-test algorithm in which positive results obtained using one assay were verified using a second assay. Results. The two nucleocapsid antibody tests were more sensitive than the spike-protein antibody test overall (70% and 70% versus 57%; P≤0.003), with pronounced differences observed using samples collected 7-14 days after symptom onset. All three assays were comparably sensitive (≥89%, P≥0.13) using samples collected >14 days after symptom onset. Specificity was higher using the nucleocapsid antibody tests (99.3% and 99.7%) compared with the spike protein antibody test (97.8%, P≤0.002). When any two assays were paired in a two-test algorithm, specificity was 99.9% (P<0.0001 to 0.25 compared with the individual assays), and positive predictive value (PPV) improved substantially with minimal effect on negative predictive value (NPV). Conclusions. Two nucleocapsid antibody tests outperformed a spike protein antibody test. Pairing two different serologic tests in a two-test algorithm improves PPV compared with the individual assays alone, while maintaining NPV.

A comprehensive antigen production and characterization study for easy-to-implement, highly specific and quantitative SARS-CoV-2 antibody assays

“…5, Table S2). This phenomenon has already been described in patients infected with SARS-CoV-1 (34,35) and was associated with higher sensitivities of other SARS-CoV-2 test systems, relying on the NP, in the early phase after an infection (36). Determining the neutralizing capacity of SARS-CoV-2 anti-RBD antibodies is critical to elucidate possible protective effects of the immune response.…”

Viral Clearance and Serological Response to SARS-CoV-2 in Kidney Transplant Recipients

“…Retrieval of serum remnant from blood samples taken for routine biochemical testing was performed in 2 patients. Sensitivities of 89.3% and 96% and specificities of 98.3% and 99.3% were reported for Euroimmun IgG [ 7 ] and Abbott IgG [ 8 ], respectively. Seronegative patients were negative for both IgGs.…”

Remote fingerstick blood collection for SARS-CoV-2 antibody testing

“…In addition, a false positive pre-pandemic specimen, which was selected as one of two pre-pandemic specimens that were false positive in the Roche assay in a cohort of 1,200 pre-pandemic specimens, was still detected in the extract sample, indicating that false positive signals indeed dilute with sample dilution, and could reflect truly cross-reactive antibodies. We also generated duplicate Mitra collections devices from contrived whole blood and performed extractions in two independent facilities and found high precision ( Figure 1C , R 2 = 0.97), highlighting the reproducibility of this testing strategy.…”

“…( B ) Contrived blood from COVID-19 patients ( n = 48) and pre-pandemic individuals ( n = 48) was collected and stored on Mitra devices and subsequently extracted and run on the Roche Elecsys assay along with paired neat serum. ( C ) Duplicate Mitra devices were used to collect contrived blood from COVID-19 patients ( n = 10), and extractions were performed in two separate facilities and run on the same Roche Elecsys assay and Roche Cobas 8000 instrument; Pearson correlation resulted in the following: coefficient of determination ( R 2 ) = 0.97, slope ( m ) = 1.03, and intercept ( b ) = 0.09. For all, the dotted black line indicates the manufacturer-established COI threshold of 1.0 (for serum) and the dotted red line indicates the new COI threshold of 0.15 (for diluted or extracted samples).…”

“…Several studies have compared the performance of these various platforms, including: Euroimmun anti-spike IgG enzyme-linked immunosorbent assay (ELISA), Bio-Rad Platelia anti-nucleocapsid total antibodies ELISA, Wantai anti-spike total antibodies ELISA, Diasorin Liaison anti-spike IgG chemiluminescence immunoassay (CLIA), Abbott Alinity anti-nucleocapsid IgG chemiluminescent microparticle-based immunoassay (CMIA), Siemens anti-spike IgG CMIA, and Roche Elecsys anti-nucleocapsid total antibodies electrochemiluminescence-based immunoassay (ECLIA) 2–4 . Based on our previous work, we chose at our institution to deploy the Roche Elecsys SARS-CoV-2 total antibody ECLIA that detects IgG, IgM, and/or IgA antibodies to SARS-CoV-2 nucleocapsid 2 , which many other centers around the world have also done 5 . While this has provided great benefit to diagnosing recent SARS-CoV-2 infection for inpatients and outpatients, this test requires collection of serum from whole blood via phlebotomy, as do the other EUA-approved serological tests mentioned above.…”