Levy-Jennings control chart

Fig. 4.1 Internal quality control results displayed on a Levis-Jen-nings chart.

An established external quality control (QC) scheme is not currently available. Pooled disease control CSF retained from other analyses is used. Aliquots of the pooled CSF are made and stored at -70°C. This CSF is analysed on five separate occasions and the mean and standard deviation determined. For an analytical/diagnostic run to proceed, analysis of QC material must provide concentration values that are within two standard deviations (plus and minus) of the calculated mean for that particular QC. Construction of Levy-Jennings type control charts provide historical information of overall performance and highlight potential deterioration in the performance of the system. 

Computer workstations can be used to monitor and integrate the functions of one or more analyzers. Typically, the workstation serves as the point of interaction with the instrument operator, accepts test orders, monitors the testing process, assists with analysis of process quality, and provides facilities for review and verification of test results. The workstation is usually directly interfaced with the LIS host, accepting downloaded test orders, and uploading test results. Most workstations have facilities to display Levy-Jennings quality control charts, to monitor the progress of each test order, and to troubleshoot the analyzers. They may also provide facilities to assist with the review of completed test results. Some workstations have rule-based software, which allows the operator to program rules for autoverification of test results (MODULAR Middleware Software). 

The most common method of presenting of data and the statistical analyzes is through Shewhart or Levy-Jennings control charts (3). These charts require the estimation of the mean and SD for each control used. 

---