Background/Case Studies: The spread of COVID-19 (COVID) infection was characterized with reports of coagulopathy and inflammatory response. Atypical levels of coagulation factors particularly fibrinogen was widely reported. Increased incidence of unexpected reactions in tests performed with specific plasma samples in the Anti-Human Globulin (AHG), Anti-IgG column agglutination tests for antibody screening (AbSc) were encountered. This reactivity presented with small clusters of red blood cells (RBCs) that were observed just below the top of the column bead layer, often with a vertical, hazy trail of RBCs below the clump and were graded as fibrin (FIB) or indeterminate (IND). Our investigation entailed determining the underlying cause of this reactivity.
Study
Design/Methods: Testing for AbSc of plasma samples from 45 patients hospitalized with COVID infections were compared with testing of 45 presumed healthy donors. IAT tests using Ortho BioVue® AHG (Anti-IgG) and AHG (Anti-IgG;C3d) (Poly) cassettes containing macromolecular potentiators were compared. Microscopy was performed to determine the mechanism of anomalous reactivity. An additional study of 30 samples with reported similar reactivity and detailed information on antibody response to the COVID virus was further evaluated.
Results/Findings: The prevalence of samples causing this “reactivity” was significantly higher in a cohort of samples from hospitalized COVID patients (24.4%) as compared to presumed healthy donors (6.7%) (p = 0.008). Unexpected reactivity of this nature was seen only with the Anti-IgG cassette and not with the Poly cassette. Formulation comparison confirmed that these reactions are dependent on the potentiator in the IgG cassette reagent. The likelihood of false reactivity was significantly higher in tests performed with plasma as compared to serum samples from the same donors (p < 0.0001). Microscopy confirmed RBC rouleaux prevents RBC migration in columns with these reactions. In the 30-patient sample set, reactivity was seen in 27 samples. Twenty-nine samples had antibody to the COVID spike protein and thirteen had nucleocapsid antibody. Analytics combining instrument results with COVID trending data from Our World in Data identified a positive correlation between increases in FIB/IND rates and rates of COVID hospitalizations globally. Stronger correlations were observed in regions with larger Anti-IgG cassette usage with R2 up to 85.2%.
Conclusions: Plasma sample fibrinogen concentration has been shown to be two-three times higher in individuals with severe cases of COVID. The combination of potentiators and samples with high fibrinogen are a contributing cause of the anomalous results encountered and can be attributed to the inflammatory response and the likely coagulopathy from COVID infection.
