Can a Half Antigen Test Strip Be Used for Accurate Testing?

The diagnosis of various infectious diseases, such as SARS-CoV-2, often relies on antigen tests. These tests utilize a test strip that is designed to detect specific antigens in a sample. But what about splitting a test strip in half? Can this result in two tests from one? This article delves into the details, providing insights based on scientific research and practical considerations.

Understanding Antigen Test Strips

Antigen tests are designed to identify the presence of specific viral proteins or antigens in a sample. These tests consist of a test strip with a series of reactive areas, each containing a different set of reagents and antibodies. The strip is engineered to give a clear and accurate result, either positive or negative, depending on the interaction between the sample and the test reagents.

Theoretical Possibility of Splitting Test Strips

Some individuals have questioned whether it would be feasible to split a test strip in half lengthwise to create two tests from one. Theoretical considerations suggest that if the strip is properly split, it may work, given that the test components are evenly distributed on the surface. Despite this, there are several critical factors to consider.

Practical Considerations

Splitting a test strip in half can lead to changes in the accuracy of the test. The test strip is calibrated to work within specific parameters, and any alteration, such as physical tampering, can disrupt the chemical interactions and thus affect the test's accuracy. Additionally, the strip's interaction with the sample and the presence of the testing medium are optimized for a complete strip, making half strips less reliable.

Scientific Evidence: Half-Straid LFAs

A study published in the Journal of the American Chemical Society presents data on the development of half-strand lateral flow assays (LFAs). In this research, the authors tested a half-strip LFA format using commercially available antibodies for detecting SARS-CoV-2. The results showed that an optical reader with sensitivity equivalent to a visual read could still accurately detect the presence of the virus. The LOD (Limit of Detection) was measured at 0.65 ng/mL, with a 95% confidence interval of 0.53 to 0.77 ng/mL. This demonstrates that half-strip LFAs can indeed provide acceptable results under certain conditions.

Accuracy and Reliability of Half-Strip Tests

Despite the theoretical and scientific evidence suggesting that half-strip tests can work, practical concerns must be addressed. Antigen tests are optimized for full strips, and any variation from the standard can lead to inaccuracies. In a large-scale manufacturing context, ensuring that the minimal amount of testing material is applied to each strip is crucial. Doubling the amount of testing material would likely lead to significant manufacturing issues and increased costs.

False Negative Rates

Antigen tests are known to have a false negative rate of 3-10% with essentially 0 false positives. Given this, the confidence in negative results from a half-strip LFA would be significantly lower. This uncertainty renders the test results meaningless for clinical decision-making purposes, where accuracy is paramount.

Conclusion

While there is some theoretical and scientific evidence that half-strip antigen tests could work, practical considerations, including accuracy, reliability, and sensitivity, suggest that they should not be used in real-world scenarios. The scale and complexity of manufacturing ensure that full strips are the most accurate and reliable option available. For optimal results, it is best to use full strips as they are intended, ensuring the highest accuracy and reliability in testing.