Abstract: Objective　To investigate the method of internal quality control for calculated laboratory tests. Methods　A method was developed using a Taylor series expansion and alternative equations to obtain the mean value and standard deviation of calculated laboratory tests as low density lipoprotein cholesterol(LDL-C) for example, and then LeveyJennings charts were printed. The results were analyzed by Westgard multirules. Results　The preparation of Levey-Jennings charts for LDL-C (and other calculated laboratory tests) and the application of Westgard multirules to calculate LDL-C (and other calculated laboratory tests) could increase the reliability of the results of the calculated laboratory tests. Conclusions　Checking the reliability of only the measured tests by internal quality control before reporting patient results may be inadequate. Applying the quality control charts and Westgard multirules to calculate tests as a part of total quality management will increase the reliability of test results.

Key words: Quality control, Levey-Jennings chart, Westgard multirule