ABSTRACT
Background/Case Studies: Use of convalescent plasma (CP) offers promise as a treatment for COVID-19. While the FDA has stated that CP donors should have SARS-CoV-2 neutralizing antibody titers greater than 160, neutralizing antibody titers are not widely available. Serologic tests to detect anti-N and anti-S antibodies are commercially available, and small studies suggest correlation between anti-S antibodies and neutralizing antibodies. Our goal was to identify the demographic and clinical characteristics of CP donors with anti-N and anti-S antibodies. Study Design/Methods: CP was collected at a hospitalbased blood donation center from 4/13/20-6/2/20. Donation inclusion criteria were: age > 18 years, confirmed prior COVID-19 infection, resolution of symptoms for > 14 days, and met all donor eligibility requirements. Samples from collections were tested with two serologic assays: Elecsys® Anti-SARS-CoV-2 (Roche) which detects IgM and IgG anti-N, and LIAISON® SARS-CoV-2 S1/S2 IgG (DiaSorin) which detects IgG anti-S1 and anti-S2. Prior work suggests that anti-S >80 AU/mL using the LIAISON® assay correlates with a 92% probability of having neutralizing antibody titers >80 and an 87% probability of having neutralizing antibody titers >160, thus this was used as a cutoff in analyses. Univariable associations between donor characteristics and LIAISON® value (<80 vs. >80 AU/mL) were tested using Fisher's exact test or Wilcoxon rank sum test. A multivariable logistic regression model of LIAISON® was fit with age, gender, race, and symptom duration as covariates. If a donor contributed multiple samples, assay information from the first sample was used. Results/Findings: Analysis included 87 donors. Donors had a median age of 34 years (26-54), and were mostly male (65.6%) and white (88.5%). Six (6.9%) were admitted to an emergency department and 3 (3.4%) were admitted to a hospital. Symptoms persisted for a median of 11 days (IQR: 8-15). Seven samples (8.0%) were non-reactive with both assays, and 9 were reactive on only one assay. There were 35 (40%) samples with >80 AU/mL on LIAISON®: all of these were reactive on Elecsys®. Asian race and longer symptom duration were associated with higher odds of LIAISON® >80 AU/mL in both univariate and multivariate analyses (OR 24.20, 95% CI 2.03-288.1 and OR 1.20, 95% CI 1.07-1.36, respectively). While not statistically significant, female donors and older donors tended to have higher odds of LIAISON® >80 AU/mL. Conclusions: Among 87 CP donors, there was high positivity across both antibody platforms and 40% had antibody levels >80 AU/mL on the LIAISON® assay. Recruiting donors with older age, female sex, Asian race and longer duration of symptoms may result in CP with higher anti-S antibody levels.