Diagnosis: Quality
• A Levey-Jennings control chart plots qualitycontrol (QC) results around their expected mean value.
• Acceptable limits for the deviation of the QC results from the expected value are determined by the laboratory.
• This is often achieved through the use of the Westgard rules, which are QC interpretive rules for statistical monitoring of assay accuracy and precision.
• Accuracy refers to how close an assay result value is with respect to the true value of the analyte.
• Accuracy can be assessed by measuring an analyte in reference material and comparing the result with the known certified concentration.
• Precision is the agreement between result values obtained by repeat measurements of a given quantity of the analyte.
