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Prozone masks elevated SARS-CoV-2 antibody level measurements.
Micaela N Sandoval1, Samuel P McClellan2, Stephen J Pont3
1Department of Epidemiology, Human Genetics, and Environmental Sciences, The University of Texas Health Science Center at Houston School of Public Health, Houston, Texas, United States of America.
Plos One
|March 28, 2024
Summary
A prozone effect can cause falsely low SARS-CoV-2 spike antibody readings in immunoassays. This phenomenon, observed in antibody surveillance, requires awareness for accurate clinical management of vaccinated or infected individuals.
Area of Science:
- Immunology
- Infectious Diseases
- Clinical Diagnostics
Background:
- Antibody surveillance programs are crucial for monitoring population immunity to SARS-CoV-2.
- Immunoassays are widely used to quantify antibody levels, but can be subject to various analytical interferences.
- The prozone effect, a known phenomenon in immunoassays, can lead to underestimation of analyte concentrations.
Purpose of the Study:
- To report and characterize the prozone effect impacting SARS-CoV-2 spike protein antibody measurements.
- To investigate the frequency of the prozone effect in a large-scale antibody surveillance program.
- To highlight the clinical implications of underestimating antibody levels due to the prozone effect.
Main Methods:
- Analysis of SARS-CoV-2 spike protein antibody levels using the Roche Elecsys® Anti-SARS-CoV-2 S immunoassay.
- Serial dilution studies were performed on samples exhibiting anomalously low antibody results.
- Prospective, longitudinal antibody surveillance data from the Texas Coronavirus Antibody Research survey (Texas CARES) were utilized.
Main Results:
- Anomalously low SARS-CoV-2 spike protein antibody levels were initially observed in the Texas CARES program.
- Serial dilution studies confirmed the presence of a prozone effect in affected participants.
- Out of 1,720 samples tested from October 2022 to March 2023, 74 additional cases of prozone effect were detected.
Conclusions:
- The prozone effect is a significant factor affecting SARS-CoV-2 spike protein antibody measurements in surveillance settings.
- This interference can lead to underestimation of antibody levels, potentially impacting clinical decisions.
- Awareness and mitigation strategies for the prozone effect are essential for accurate assessment of immunity in individuals with high antibody titers.
