S1 Data -

BackgroundIdentifying a specific threshold level of SARS-CoV-2 antibodies that confers protection in immunocompromised patients has been very challenging. The aim was to assess the threshold of 264 binding antibody units (BAU)/ml using four different SARS-CoV-2 antibody assays (Abbott, Beckman, Roche, and Siemens) and to establish a new optimal threshold of protection for each of the four antibody assays.MethodsThis study was performed on data retrieved from 69 individuals, who received at least one dose of the Pfizer/BioNTech BNT162b2 or Moderna COVID-19 vaccine (Spikevax) at the Alphabio Laboratory in Marseille, France (European Hospital, Alphabio–Biogroup). The results were compared to the percent inhibition calculated using a functional surrogate of a standardized virus neutralization test (Genscript).ResultsSamples from 69 patients were analyzed. For a reference cutoff of 264 BAU/ml, assays showed moderate to good overall concordance with Genscript: 87% concordance for Abbott, 78% for Beckman, 75% for Roche, and 88% for Siemens. Overall concordance increased consistently after applying new thresholds, i.e., 148 BAU/ml (Abbott), 48 (Beckman), 559 (Roche), and 270 (Siemens).ConclusionWe suggest specific adjusted thresholds (BAU/ml) for the four commercial antibody assays that are used to assess pre-exposure prophylaxis in immunocompromised patients.</div

Agreement between antibody binding assays and Genscript sVNT positive and negative results according to the reference cutoff (264 BAU/ml).

Agreement between antibody binding assays and Genscript sVNT positive and negative results according to the reference cutoff (264 BAU/ml).</p

ROC curves for each antibody binding assay according to Genscript sVNT.

ROC curves for each antibody binding assay according to Genscript sVNT.</p

Baseline characteristics.

BackgroundIdentifying a specific threshold level of SARS-CoV-2 antibodies that confers protection in immunocompromised patients has been very challenging. The aim was to assess the threshold of 264 binding antibody units (BAU)/ml using four different SARS-CoV-2 antibody assays (Abbott, Beckman, Roche, and Siemens) and to establish a new optimal threshold of protection for each of the four antibody assays.MethodsThis study was performed on data retrieved from 69 individuals, who received at least one dose of the Pfizer/BioNTech BNT162b2 or Moderna COVID-19 vaccine (Spikevax) at the Alphabio Laboratory in Marseille, France (European Hospital, Alphabio–Biogroup). The results were compared to the percent inhibition calculated using a functional surrogate of a standardized virus neutralization test (Genscript).ResultsSamples from 69 patients were analyzed. For a reference cutoff of 264 BAU/ml, assays showed moderate to good overall concordance with Genscript: 87% concordance for Abbott, 78% for Beckman, 75% for Roche, and 88% for Siemens. Overall concordance increased consistently after applying new thresholds, i.e., 148 BAU/ml (Abbott), 48 (Beckman), 559 (Roche), and 270 (Siemens).ConclusionWe suggest specific adjusted thresholds (BAU/ml) for the four commercial antibody assays that are used to assess pre-exposure prophylaxis in immunocompromised patients.</div

Boxplots for each antibody binding assay according to Genscript sVNT positive and negative results.

Solid reference line represents 264 binding antibody units (BAU)/ml cutoff (2.4 Log). The Wilcoxon test for pairwise comparisons yielded P < 0.0001 for all comparisons.</p

Range, mean, median and standard deviation according to assays (POC and Lab).

<p>Range, mean, median and standard deviation according to assays (POC and Lab).</p

Between-day imprecision of central laboratory automated analyzers (Lab).

<p>Between-day imprecision of central laboratory automated analyzers (Lab).</p

Between-day imprecision of the Point-of-Care Siemens RAPIDPoint 500 blood gas system (POC).

<p>Between-day imprecision of the Point-of-Care Siemens RAPIDPoint 500 blood gas system (POC).</p