What is an antigen test?

Table of Contents

1. Introduction
2. Understanding Antigen Tests
   1. Principle of Antigen Testing
   2. Accuracy and Sensitivity
   3. Applications
3. Immuno Company Solutions
4. Conclusion
5. References

Introduction

Antigen tests have become a pivotal tool in the diagnosis and management of infectious diseases, especially during the COVID-19 pandemic. These tests are designed to quickly identify the presence of specific proteins from viruses, providing crucial data for public health responses.

Understanding Antigen Tests

Principle of Antigen Testing

Antigen tests, sometimes referred to as rapid diagnostic tests (RDTs), detect the presence of a specific viral antigen, which implies an active infection. These tests work by using antibodies tailored to detect antigens, usually through a nasal or throat swab sample. When the sample is applied to the test apparatus, any viral antigen present binds to the specific antibodies, leading to a visible result.

Accuracy and Sensitivity

While antigen tests offer rapid results, they generally possess lower sensitivity compared to molecular tests like RT-PCR. Sensitivity rates for antigen tests are typically in the range of 84-97%, whereas specificity is often higher, ranging between 93-99%. False negatives can occur if the viral load is below the detectable threshold at the time of testing.

Applications

Antigen tests are commonly used in settings where quick results are essential, such as large-scale screenings in schools, workplaces, and airports. These tests provide a timely identification of infectious individuals, helping to curb the spread by enabling prompt isolation and treatment measures.

Immuno Company Solutions

Companies like Abbott, Quidel, and BD Veritor have developed antigen test kits that meet the needs of different settings by offering varied solutions in terms of usability, speed, and accuracy. For example, the Abbott BinaxNOW test can deliver results in as little as 15 minutes with a sensitivity of approximately 84.6% and a specificity of 98.5%. Quidel's Sofia SARS Antigen FIA offers a sensitivity of 96.7% with a specificity of 100% when evaluated in a clinical setting.

Conclusion

Antigen tests remain a key component in the management of infectious diseases due to their speed and ease of use. Despite limitations in sensitivity, their role in providing rapid diagnostics is indispensable, especially in large-scale public health initiatives.

References

1. Abbott. (2020). BinaxNOW COVID-19 Ag Card [PDF document]. Retrieved from https://www.globalpointofcare.abbott/en/product-details/binaxnow-covid-19-ag-card.
2. Quidel Corporation. (2020). Sofia SARS Antigen FIA [PDF document]. Retrieved from https://www.quidel.com/immunoassays/rapid-sars-antigen-test
3. U.S. Centers for Disease Control and Prevention. (2021). Interim Guidance for Antigen Testing for SARS-CoV-2. Retrieved from https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.