Are there any reasons to use three levels of quality control materials instead of two and if so, what are the arguments?

Are there any reasons to use three levels of quality control materials instead of two and if so, what are the arguments? Quality control (QC) materials are essential in laboratory medicine to ensure the accuracy and reliability of patient test results. They help to monitor the performance of laboratory instruments, reagents, and personnel over time. QC materials come in different levels, typically categorized as two (low and high) or three (low, medium, and high). The choice between two or three levels depends on various factors, and both options have their own advantages and limitations. The choice between two or three levels of quality control materials in laboratory medicine depends on a combination of clinical, regulatory, resource, and test-specific factors. Laboratories should carefully consider their needs and select the appropriate QC strategy to ensure the accuracy and reliability of their test results, while considering practical limitations. A typical example for using a three levels QC material is cardiac troponin testing, as it is necessary to use a specific control material with concentration close to the limit of quantitation, along with two other levels with concentrations close to the upper reference limit (URL) and to the upper part of the measuring range.