Modified Levey-Jennings charts for calculated laboratory tests

Background: In clinical laboratories, many test results such as low-density lipoproteins can be calculated using the results of specifically measured tests. However, quality control programs deal with only measured tests and there is no quality control procedure for calculated tests. I aimed to modify the Levey-Jennings chart for calculated tests as part of a total quality system. Methods: I developed a method using a Taylor series expansion and alternative equations to obtain the standard deviation of calculated tests and then prepared Levey-Jennings charts for these tests. Results: Preparation of Levey-Jennings charts for low-density lipoproteins ( and other calculated tests) was simple, and using this chart increased the reliability of calculated test results. Conclusion: Checking only measured tests by quality control procedures before reporting patient results may be inadequate. Preparation of Levey-Jennings charts for calculated tests as part of total quality management will increase the reliability of test results.