OA3-AM24-ST-26 - Comparison of SARS-CoV-2 IgG Antibodies between Convalescent Plasma and Conventional Plasma Units

Saturday, October 19, 2024

1:45 PM - 2:45 PM

Location: 342

CE: Zero

Presenting Author(s)

Andrew Sulaiman, DO, PhD (he/him/his)

PGY2 Clinical Pathology Resident
Johns Hopkins University
Parkville, Maryland, United States

Disclosure(s): No financial relationships to disclose

PDF

Disclosure(s):

Andrew Sulaiman, DO, PhD: No financial relationships to disclose

Background/Case Studies: AABB guidelines recommend the use of high-titer COVID-19 convalescent plasma (CCP) for patients with SARS-CoV-2 at high-risk of disease progression and those who are immunosuppressed. CCP is still being utilized today, but units are expensive and scarce that sometimes necessitates the use of incompatible plasma. The FDA has defined high-titer units. Given that a significant portion of the US population has experienced SARS-CoV-2 infection, we hypothesized that fresh frozen plasma (FFP) units would exhibit SARS-CoV-2 antibody levels comparable to those found in CCP.

Study

Design/Methods:

53 CCP and 94 FFP units were obtained from local and regional blood suppliers. SARS-CoV-2 antibodies were quantitatively measured using a multiplex electrochemiluminescence immunoassay from MesoScale Diagnostics to assess SARS-CoV-2 Nucleocapsid, SARS-CoV-2 S1 receptor binding domain (RBD) and the SARS-Cov-2 Spike antibodies. Spike antibodies against COVID-19 variants Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2; AY.4), and Omicron (B.1.1.529; BA.1) were also assessed. Antibody distributions were assessed by group using histograms. Medians, 25^th, and 75^th percentiles for each analyte were calculated. Boxplots comparing the distributions were generated, and statistically significant differences in antibody distributions by group were assessed using the Wilcoxon rank sum test.

Results/Findings: CCP units were manufactured during 11/12/23 to 3/4/24 and FFP units were manufactured from 9/8/23 to 4/22/24. Samples were run at a dilution of 1:500,000 to account for antibody levels in the 90% of FFP and 66% of CCP units being above the limit of detection at the standard 1:5,000 dilution. CCP units had higher levels of SARS-CoV-2 Nucleocapsid, RBD, Spike and Spike Variant antibodies. The median SARS-CoV-2 S1 RBD antibody concentration 10,283 AU/mL in FFP compared to 89,285 AU/mL in CCP samples (p < 0.001). SARS-CoV-2 Spike and Spike antibodies against COVID-19 variants ranged from a median signal interquartile range of 205.3-861,004 AU/mL in FFP compared to 3832.2-2,489,911 AU/mL in CCP samples (p < 0.001 for all comparisons). Median SARS-CoV-2 Nucleocapsid antibody levels were 851.9 AU/mL in FFP compared to 33,776.3 AU/mL in CCP samples (p < 0.001).

Conclusions:

CCP must contain high titers of anti-SARS CoV-2 antibodies. Based on the median interquartile ranges, randomly selected FFP units have overlapping SARS CoV-2 antibody levels with CCP units. SARS CoV-2 Nucleocapsid antibody concentrations demonstrated the largest discrepancy between CCP and FFP units; however, this is only indicative of prior infection. As CCP remains difficult to obtain, FFP units may be of clinical utility.