Clinical And Analytical Performance Of An Automated Serological Test That Identifies S1/S2 Neutralizing IgG In Covid-19 Patients Semiquantitatively

Abstract

word count: 246 20 Text word count: 3188 21 22 4 ABSTRACT 23BACKGROUND. In the Covid-19 pandemic, highly selective serological testing is 24 essential to define exposure to SARS-CoV-2 virus. Many tests have been developed, 25 yet with variable speed to first result, and of unknown quality, particularly when 26 considering the prediction of neutralizing capacity. 27 OBJECTIVES/METHODS. The LIAISON ® SARS-CoV-2 S1/S2 IgG assay was designed 28 to measure antibodies against the SARS-CoV-2 native S1/S2 proteins in a standardized 29 automated chemiluminescent assay. Clinical and analytical performance of the test 30 were validated in an observational study using residual samples (>1500) with positive or 31 negative Covid-19 diagnosis. 32RESULTS. The LIAISON ® SARS-CoV-2 S1/S2 IgG assay proved highly selective and 33 specific, and offers semiquantitative measures of serum or plasma levels of anti-S1/S2 34 IgG with neutralizing activity. The diagnostic sensitivity was 91.3% and 95.7% at >5 or 35 ≥15 days from diagnosis respectively, and 100% when assessed against a neutralizing 36 assay. The specificity ranged between 97% and 98.5%. The average imprecision of the 37 assay was <5 % coefficient of variation. Assay performance at 2 different cut-offs was 38 evaluated to optimize predictive values in settings with different % disease prevalence. 39 CONCLUSIONS. The automated LIAISON ® SARS-CoV-2 S1/S2 IgG assay brings 40 efficient, sensitive, specific, and precise serological testing to the laboratory, with the 41 capacity to test large amounts of samples per day: first results are available within 35 42 minutes with a throughput of 170 tests/hour. The test also provides a semiquantitative 43 measure to identify samples with neutralizing antibodies, useful also for a large scale 44 screening of convalescent plasma for safe therapeutic use. 45 5 IMPORTANCE 46With the worldwide advance of the COVID-19 pandemic, efficient, reliable and 47 accessible diagnostic tools are needed to support public health officials and healthcare 48 providers in their efforts to deliver optimal medical care, and articulate sound 49 demographic policy. DiaSorin has developed an automated serology based assay for 50 the measurement of IgG specific to SARS CoV-2 Spike protein, and tested its clinical 51 performance in collaboration with Italian health care professionals who provided access 52 to large numbers of samples from infected and non-infected individuals. The assay 53 delivers excellent sensitivity and specificity, and is able to identify samples with high 54 levels of neutralizing antibodies. This will provide guidance in assessing the true 55 immune status of subjects, as well as meeting the pressing need to screen donors for 56 high titer convalescent sera for subsequent therapeutic and prophylactic use. 57 58 SARS-CoV-2, the virus responsible for the Covid-19 pandemic, has spread at an 59 alarming rate since the first case tracked back to mid-November of 2019 in Wuhan 60 China (1). Contraction and subsequent transmission accrue...

Performance characteristics of five immunoassays for SARS-CoV-2: a head-to-head benchmark comparison

“…Manufacturers' sensitivity estimates ranged from 96·8% to 100% on samples taken at least 14 days post symptom onset or RT-PCR, and specificity estimates ranged from 98·5% to 99·8% on pre-pandemic samples ( appendix p 14 ). 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18…”

Association between SARS-CoV-2 neutralizing antibodies and commercial serological assays

“…For instance, the LIAISON SARS-CoV-2 S1/S2 IgG assay claims high agreement with neutralizing antibodies. However, the cutoff titer used for the neutralizing assay was 1:40; far below that recommended by FDA for convalescent plasma therapy (13). If neutralizing antibodies >1:256 are required for protection, then commercial assays at the current cutoffs may have limited utility for identifying patients with protective antibodies; with NPA between 18-40% for the assays tested in this study.…”

“…Tang 4 Despite widespread interest in neutralizing antibodies, methods for their detection and quantification are relatively low-throughput and limited to Biosafety Level 3-equipped research laboratories. While high-throughput methods have emerged, most rely on recombinant Vesicular Stomatitis Viruses (VSV) engineered to express a portion of the SARS-CoV-2 viral spike protein, and their subsequent entry into cell lines (12)(13)(14).…”

Comparative Evaluation of Three Serologic Assays for the Identification of SARS-CoV-2 Antibodies

“…With 1 100% PNA and 100% PPA in the convalescent group, this study describes a more favorable 1 diagnostic accuracy. One of the studies provided the median positive quantitative results for 1 comparison, which ranged from 8-96.3 AU/mL, with 96.3 AU/mL representing their most 1 acutely ill subjects [11]. In comparison, the median positive result in this study was 190 AU/mL, 1 which may suggest our high PPA is a consequence of high patient acuity.…”

“…Two peer-reviewed articles and three studies released as pre-prints specifically reported on the 1 accuracy of the DiaSorin SARS-CoV-2 serologic assay in comparison to PCR, with a range of 1 96.8-100% for specificity and 77.8-95.7% for sensitivity in convalescent patients [8][9][10][11][12]. With 1 100% PNA and 100% PPA in the convalescent group, this study describes a more favorable 1 diagnostic accuracy.…”