In the laboratory, quality control (QC) is the practice of ensuring that the laboratory instruments and various test methodologies used on those instruments are performing accurately.
In the laboratory, quality control is run with a series of samples containing low, normal, and high levels of an analyte. A laboratory professional runs those samples on the analyzer. The results produced from the analyzer are compared against those listed by the manufacturer. If the results are within the manufacturer's acceptable limits, then patient testing can proceed. If the results are not within the acceptable limits, the laboratory must troubleshoot. After troubleshooting, quality control must be re-run before patient testing can be performed. No diagnostic testing can be performed until quality control results are within the acceptable limits.
CLIA regulates a laboratory's quality by outlining the frequency of quality control runs. For example, automated hematology and coagulation analyzers require that two levels of controls (low, normal, or high levels of an analyte) are measured and evaluated every 8 hours of testing and every time a reagent on the analyzer is changed.