USING SHEWHART-P CONTROL CHARTS OF EXTERNAL QUALITY-ASSURANCE PROGRAMDATA TO MONITOR ANALYTICAL PERFORMANCE OF A CLINICAL-CHEMISTRY LABORATORY

We have investigated the application of Shewhart's p control charts in our external quality-assurance program to monitor the long-term perfo rmance of our laboratory's analytical quality. The p control charts ha ve been able to detect long-term changes in our laboratory's analytica l performance that would have been difficult to detect by more-convent ional techniques, We have explored methods for interpreting these char ts as well as some of their limitations, which include minimum subgrou p size and dependence on constant specification Limits. These charts m ay be not only a simple method for the long-term monitoring of analyti cal performance of a laboratory, but also of use to the organizers of external quality-assurance programs.