ABSTRACT
Background/Case Studies: Blood donor based serosurveillance is a convenient and cost-effective strategy to monitor the extent of the COVID-19 pandemic and allows the detection of asymptomatic and recovered cases. The RESPONSE (REDS-IV-P Epidemiology, Surveillance and Preparedness of the Novel SARS-CoV-2 Epidemic) study conducted monthly cross-sectional serosurveys of 1000 routinely obtained donor samples in 6 metropolitan regions (see table). Study Design/Methods: Samples were captured monthly from March or April through June 2020. Siteswere selected based on reports of epidemic activity or as low prevalence control regions. Donations from COVID- 19 convalescent plasma donors were excluded. Coded samples, with routinely collected demographic data and zip code of residence, were tested for SARS-CoV-2 antibodies using the Ortho VITROS anti-SARS-CoV-2 S1 Total Ig (data reported below) with planned confirmation of reactivity on Roche Elecsys® NC Anti-SARS-CoV-2 and a pseudovirus-based neutralization assay. Results/Findings: Table 1 shows donor seroreactivity with 95% CI. For all sites, seroreactivity was <1.0% (range 0.1%-0.9%) at the beginning of the surveillance period. Donor seroreactivity in New York City (NYC) was about 10-fold higher in April through June as compared to March and was much higher than in other locations. There were modest increases in seroreactivity over the study timeframe for all other sites. Conclusions: Modest increases in seroreactivity from baseline were found in all sites, with the largest increase in NYC. SARS-CoV-2 antibody testing of routinely obtained blood donor samples allows for detection of asymptomatic and recovered COVID-19 cases and enables future estimation of infection incidence by geographic and other demographic parameters. This approach will be used in a significantly expanded CDC National serosurveillance study involving all 50 states over 18 months.
ABSTRACT
Background/Case Studies: The efficacy of COVID-19 convalescent plasma (CCP) to treat COVID-19 is hypothesized to be associated with the concentration of neutralizing antibodies (nAb) to SARS-CoV-2. While high capacity, automated serologic assays to detect binding antibodies (bAb) have been developed, complex nAb assays are not easily adaptable to high-throughput testing. We sought to determine the effectiveness of using surrogate bAb signalto- cutoff ratio (S/CO) in predicting nAb titers using a pseudovirus reporter viral neutralization (RVPN) assay. Study Design/Methods: CCP donor serum collected by 3 large US blood collectors was tested with a bAb assay (Ortho Diagnostic VITROS® Anti-SARS-CoV-2 Total, CoV2T) and a nAb RVPN assay. Although EUA approved as a qualitative assay, CoV2T reports a semi-quantitative S/CO. The RVPN assay uses a pseudovirus construct with native S-protein and target cell lines overexpressing ACE2 receptor and TMPRSS2 protease. Serially diluted serum is mixed with SARS-CoV-2 pseudovirus to assess inhibition of viral entry in culture and reported as titers resulting in 50% neutralization of virus infectivity (NT50) by nonlinear regression analysis. CoV2T prediction effectiveness at several S/CO thresholds was evaluated for various RVPN nAb NT50 titers using receiver operating characteristic analysis. Results/Findings: 753 CCP donations were tested with median CoV2T S/CO of 71.2 (range 0.1-919) and median NT50 of 527.5 (range <40 to >10,240). The prevalence of CCP donors with NT50 over various target n-Ab titers were 86% >80, 76% >160, and 45% >640. Increasing CoV2T reactivity threshold reduces sensitivity to predict the target NT50 titer while specificity to identify those below nAb threshold increases for all targeted NT50s (Table 1). As the targeted NT50 is increased from >80 to >640, the positive predictive value falls dramatically while the negative predictive value increases, thus S/CO thresholds are less able to predict donors who have the target NT50 titer but more able to predict those donors who do not meet it. Conclusions: The selection of targeted nAb titer for clinical use will significantly impact availability of CCP for transfusion. Product release with CoV2T assay S/CO thresholds must balance the risk of releasing products below minimum target nAb titer and the cost of false negatives (CCP units below the threshold with adequate nAb titers). A two-step testing scheme may be optimal, with nAb testing performed on CoV2T reactive samples with S/CO values below the release threshold.
ABSTRACT
Background/Case Studies: SARS-CoV-2 RNA has been detected by PCR in plasma, serum or whole blood specimens from hospitalized patients in studies from multiple countries. For asymptomatic individuals, several reports have described detection of SARS-CoV-2 RNA in plasma in a small number of blood donors, whereas other reports showed no detection of SARS-CoV-2 RNA in whole blood, serum or plasma from asymptomatic individuals including blood donors. No cases of transfusion-transmission of SARS-CoV-2 (or other human coronaviruses) have been reported, nor has virus been isolated from blood samples by tissue culture. We tested residual volumes of donor plasma from mini-pools (MPs) used for routine nucleic acid testing (NAT) screening to determine the frequency of SARS-CoV-2 RNAemia in blood donors in six US metropolitan regions (New York, Seattle, San Francisco, Los Angeles, Boston, Minneapolis). Study Design/Methods: Blood donations collected from 7 March 2020 to 30 June 2020 were tested for SARS-CoV-2 RNA. Donations were tested in plasma MPs of 6 or 16 donations (MP16 format for five regions and MP6 format for Seattle), targeting 500 MPs per region per month, using the Grifols Procleix SARS-CoV-2 transcriptionmediated amplification (TMA) assay on the Procleix Panther system. The test has a 95% limit of detection (LOD) of 16.5 copies/mL (95% CI, 12.8 to 23.6 copies/mL) by probit analysis. A confirmed positive result was defined by the detection of viral RNA upon repeat testing using the same assay and an alternate target region TMA assay (Grifols SARS-CoV-2 confirmatory TMA assay) with comparable sensitivity. Positive MPs were further tested using the Ortho VITROS anti-SARS-CoV-2 Total Ig test to detect antibodies and diluted 4-fold and tested using the Procleix SARS-CoV-2 TMA assay to determine whether the viral load was close to the 95% LOD. Results/Findings: A total of 8,496 MPs16 and 1,998 MPs 6, corresponding to ∼147,000 blood donations, were tested for SARS-CoV-2 RNA. One confirmed positive MP16 sample from a March donation in San Francisco was identified (0.0007% [95% CI 0.000035-0.004%]). The MP was negative for antibody and nonreactive when diluted 4-fold, suggesting a viral load below 1,000 RNA copies/mL in the individual donation. Conclusions: Blood donation MP-NAT indicated that SARS-CoV-2 RNAemia is rare, and when detected the RNA was at low concentration. Although future studies to determine the infectivity of RNA-positive plasma are warranted and in progress, these findings are reassuring with respect to transfusion safety and support current recommendations from WHO and regulatory agencies to not screen donors by NAT.