This step in assay validation ensures that the results are reliable over repeated tests. What is it?

The focus on ensuring that results are reliable over repeated tests connects directly to method validation. Method validation is the process that demonstrates whether a particular analytical procedure is suitable for its intended purpose, which includes assessing the consistency and reliability of results obtained from repeated tests. It usually involves multiple parameters such as accuracy, precision, specificity, linearity, and range, among others. By validating a method, analysts can confirm that the assay produces consistent results for the same sample under the same conditions, which is essential for credibility in analytical testing.

On the other hand, while instrument performance and assay calibration are critical components of an analytical process, they do not solely encompass the comprehensive nature of method validation. Instrument performance focuses on the reliability and accuracy of the instrumentation used, and assay calibration refers to the process of establishing a relationship between instrument responses and known concentrations of analytes. Quality control issues pertain to the systems in place to monitor and maintain the quality of results throughout the testing process but do not define the overall reliability of a method as a whole.

Thus, method validation is the correct answer because it specifically addresses the essential aspects that ensure the reliability of analytical results across multiple tests.