Correlation between SARS-COV-2 antibody screening by immunoassay and neutralizing antibody testing

Area of Science:

• Immunology
• Virology
• Transfusion Medicine

Background:

• Convalescent plasma (CP) is a potential COVID-19 treatment, but its efficacy relies on high neutralizing antibody (nAb) titers.
• Quantifying nAbs is challenging due to limited assay availability.
• Predicting high nAb titers in CP donors is essential for effective treatment.

Purpose of the Study:

• To develop and evaluate strategies for predicting high nAb titers in CP donors.
• To assess the utility of anti-SARS-CoV-2 immunoassays and clinical data for this prediction.

Main Methods:

• 214 CP donors were tested for anti-SARS-CoV-2 IgG using EUROIMMUN and Abbott immunoassays.
• nAb quantification was performed using the Cytopathic Effect-based Virus Neutralization test.
• Three criteria (C1, C2, C3) were evaluated to predict nAb titers ≥1:160, incorporating immunoassay results and clinical variables.

Main Results:

• Both EUROIMMUN and Abbott immunoassays showed similar performance in predicting nAb titers.
• Criterion C1 (ROC curve) achieved 76.1% accuracy with S/CO = 4.65.
• Criterion C2 (decision tree with IA results) showed 76.1% accuracy with S/CO ≥4.57.
• Criterion C3 (decision tree with IA and clinical data) achieved 71.6% accuracy, considering S/CO thresholds and symptom recency.

Conclusions:

• SARS-CoV-2 IgG immunoassays, specifically S/CO values, can effectively predict high nAb titers.
• The proposed criteria offer high efficacy in identifying CP donors with ≥1:160 nAb titers.
• These predictive strategies can aid in selecting suitable CP for COVID-19 treatment.