QUALITY CONTROL

• Quality control in the medical laboratory is a statistical process used to monitor and evaluate the analytical process that produces patient results
• Requirements for a statistical process in quality control include:

  • Regular testing of quality control products along with patient samples
  • Comparison of quality control results to specific statistical limits (ranges)
• Good laboratory practice requires testing normal and abnormal controls for each test at least daily to monitor the analytical process
• The mean (or average) in quality control is the laboratory’s best estimate of the analyte’s true value for a specific level of control
• Standard deviation in quality control quantifies how close numerical values are in relation to each other, providing an estimate of test consistency at specific concentrations
• In cases of instability of results, questions are used to investigate the problem, such as changes in reagents, maintenance, electrode cleaning, pipette operation, and test operator
• The Levey-Jennings chart is a horizontal graph of quality control data used to provide a visual representation of quality control data generated over time
• Trends in quality control data indicate a gradual loss of reliability in the test system, while shifts represent a sudden and dramatic positive or negative change in test system performance
• Random error in quality control results is any deviation away from an expected result, with acceptable random error defined by standard deviation
• Westgard Rules are used to evaluate the quality of analytical runs in medical laboratories, with rules like 12s, 13s, 22s, R4s, 31s, 41s, and 10x to identify errors and trends