From these data, the means and standard deviations were calculated to be: Control 1Įach of the two control materials will be analyzed once per run, providing a total of two control measurements per run. The materials were analyzed once per day for a period of twenty days. Example applicationįor a cholesterol method, two different commercial control products have been selected that have concentrations near the important medical decision levels of 200 mg/dL and 240 mg/dL identified by the National Cholesterol Education Program (NCEP) guidelines for test interpretation. See QC - The Planning Process for a description of the approach, tools, and technology available to select QC procedures on the basis of the quality required for a test and the performance observed for a method. See QC - The Calculations for detailed information about calculating the mean and standard deviation. See QC - The Materials for more information about selecting appropriate control materials. This assumes you already have (a) selected appropriate control materials, (b) analyzed those materials to characterize method performance by collecting a minimum of 20 measurements over at least 10 days, (c) calculated the mean and standard deviation of those data, and (d) selected the number of control measurements to be used per run and (e) selected the control rules to be applied.
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This exercise is intended to show, in step-wise fashion, how to construct a Levey-Jennings control chart, plot control values, and interpret those results. You can link here to an online calculator which will calculate control limits for you. An updated version is now available in Basic QC Practices, 3rd Edition Please Note: This article is from the first edition. Barry, co-author of Cost-Effective Quality Control: Managing the Quality and Productivity of Analytical Processes, provides a primer on how to construct, use, and interpret the Levey-Jennings chart. We can no longer take for granted that everyone knows how to build a control chart, plot the control values, and interpret those results correctly. This lesson discusses one of the cornerstones of QC practice.
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