Related Experiment Video
Updated: Aug 22, 2025
Dynamic Monitoring of Seroconversion using a Multianalyte Immunobead Assay for Covid-19
Published on: February 16, 2022
SARS-CoV-2 IgG Levels Allow Predicting the Optimal Time Span of Convalescent Plasma Donor Suitability
Sandra Laner-Plamberger1, Nadja Lindlbauer1, Lisa Weidner2
1Department for Transfusion Medicine, University Hospital of Salzburg, Paracelsus Medical University Salzburg, Müllner-Hauptstraße 48, 5020 Salzburg, Austria.
Insights
This study found that semi-quantitative IgG ratio values accurately predict antibody functionality in convalescent plasma (CP) for COVID-19. High IgG levels indicate suitability for CP donation for a median of 134 days, guiding optimal plasma collection.
Area of Science:
- Immunology
- Infectious Diseases
- Transfusion Medicine
Background:
- Convalescent plasma (CP) is a century-old treatment for infectious diseases, recently applied to COVID-19.
- Identifying suitable donors and optimal donation timing for CP is crucial for effective treatment.
- Assessing functional antibody levels in donors remains a challenge.
Purpose of the Study:
- To evaluate the correlation between anti-SARS-CoV-2 IgG antibody levels and in vitro antibody functionality in CP.
- To determine the optimal time frame for CP donation based on antibody levels.
- To provide guidance for plasma collection centers on donor selection and timing.
Main Methods:
- Retrospective analysis of 189 CP donations from 66 donors.
- Measurement of anti-SARS-CoV-2 anti-S IgG antibody levels using semi-quantitative ratios.
- Time-to-event analysis to predict donor suitability duration.
Main Results:
- A significant correlation was observed between semi-quantitative IgG ratio values and in vitro antibody functionality.
- Donors with high IgG ratios remained suitable for CP donation for a median of 134 days.
- Donors with lower IgG ratios were suitable for a median of 53 days.
Conclusions:
- Semi-quantitative IgG ratio values are reliable indicators of functional antibody levels in CP.
- This finding enables plasma collection centers to optimize donor selection and donation timing for COVID-19 CP.
- The study supports using routine laboratory IgG measurements to guide CP donation practices.
Abstract:
Convalescent plasma (CP) has been in use for the treatment of numerous infectious diseases for more than a century, recently also for coronavirus disease 2019 (COVID-19). A major challenge for this treatment is identifying suitable donors with sufficient levels of functional antibodies and to determine the optimal time span for CP donation. In this retrospective study, we analyzed 189 CP donations of 66 donors regarding anti-SARS-CoV-2 anti-S IgG antibody levels. We found a significant correlation between the semi-quantitative SARS-CoV-2 IgG ratio values and in vitro antibody functionality. A time-to-event analysis allowed us to predict the optimal time span of COVID-19 CP donor suitability. We found that high IgG ratio values, which significantly correlate with high in vitro antibody functionality, were suitable for CP donation for a median of 134 days after the first CP donation. Donors with lower IgG ratios were suitable for a median of 53 days. Our data support plasma collection centers to determine optimal points in time for CP donation by means of widely used semi-quantitative laboratory IgG ratio values.
