Which term describes the materials run to verify ongoing performance of a test system during testing?

• A. Calibration standards
• B. Patient samples
• C. Quality control samples
• D. Dilution standards

Answer: (C)

Quality control samples are used to verify ongoing performance of a test system during testing. These materials have known, valued results and are run with every analytical batch to check that the entire testing process—instrument performance, reagent integrity, calibration status, and the analyst’s technique—is functioning correctly. When QC results fall within predefined acceptable ranges, confidence in the accuracy and precision of patient results is maintained; when they drift or go out of range, it signals a potential issue that needs investigation and corrective action before reporting patient results. This monitoring is distinct from calibration standards, which establish the instrument’s response to known values at set intervals, and from patient samples, which are actual specimens not used for ongoing system checks. Dilution standards are used to evaluate assay linearity and working range rather than routine performance surveillance.