(P-PH-4) Leveraging access to blood donor samples through a central testing lab. to support nationwide public health serosurveillance: Impact of delayed sample processing on SARS-CoV-2 serological results

Vitalant Research Institute (VRI) and American Red Cross (ARC) capitalized on their unique access to blood donor samples with nationwide representation through their common central blood screening laboratory Creative Testing Solutions (CTS) to perform serological testing for a nationwide SARS-CoV-2 blood donor based serosurveillance program. Residual blood donor samples were captured after routine blood screening at CTS, with plasma or serum separated and aliquoted from whole blood tubes at CTS or ARC and tested fresh or after refrigerated or frozen storage. This study evaluated the impact of 1) delayed processing and 2) prolonged refrigerated or frozen storage of samples on performance of anti-SARS-CoV-2 antibody (Ab) assays.

Study

Design/Methods:

Serological testing was performed using the Ortho Clinical Diagnostic quantitative anti-SARS-CoV-2 Spike (S) IgG (anti-S IgG) and anti-Nucleocapsid (N) Total Ig (anti-N total Ig) assays. Anti-S Ab levels (BAU/mL) and anti-N Abs signal to cutoff ratios (S/CO) for 10 paired plasma and serum samples aliquoted after a delay of up to 67 days post-collection, 20 paired plasma and serum samples stored at 4^oC for ≤40 days and 2,800 plasma samples frozen for ≤202 days were compared to those in Day 5 samples tested fresh or after a freeze/thaw cycle. Proportional Bland-Altman plots and statistics were computed (bias, 95% limits of agreement).

Results/Findings: Ab reactivity in paired serum and plasma were stable over time regardless of processing delays or prolonged storage. Bland Altman analyses confirmed that only minor deviations were observed after freezing or after extended periods before processing and testing with small biases and tight limits of agreement (Table 1).  

Conclusions:

This study provided compelling evidence that delays resulting from the challenges experienced by large-scale research operations did not significantly impact the performance of Ortho serological assays. Furthermore, the adequacy of our research operation structure was demonstrated and can be leveraged to support nationwide public health surveillance and the monitoring of other infectious diseases in the US blood donor population to inform public health policies during infectious disease outbreaks.