How to Determine When SARS-CoV-2 Antibody Testing Is or Is Not Useful for Population Screening: A Tutorial

Area of Science:

• Epidemiology
• Immunology
• Public Health

Background:

• Enzyme-linked immunosorbent assay (ELISA)-based antibody tests for SARS-COV-2 are crucial for pandemic management.
• These tests aid in assessing individual immunity and estimating asymptomatic spread, informing policy effectiveness.
• Test utility is critically dependent on the prevalence of the disease in the population.

Purpose of the Study:

• To introduce tools for evaluating the usefulness of SARS-COV-2 antibody testing in various contexts.
• To aid in interpreting antibody test results, especially when infection rates are low.
• To support both clinical decision-making and public health policy regarding testing strategies.

Main Methods:

• Development and presentation of natural frequency trees.
• Development and presentation of positive and negative predictive value graphs.
• Application of these tools to assess antibody test performance under different prevalence scenarios.

Main Results:

• Natural frequency trees and predictive value graphs provide a clear visual assessment of test usefulness.
• These tools highlight how low infection rates can lead to a high proportion of false positives.
• The effectiveness of antibody testing is demonstrated to be highly context-dependent.

Conclusions:

• Natural frequency trees and predictive value graphs are valuable tools for understanding antibody test utility.
• These tools can improve the interpretation of individual immunity status and population spread estimates.
• Informing policy and clinical practice through better understanding of test performance in specific epidemiological contexts.