Don't rely solely on Sigma values to determine QC frequency

There are at least four other factors that should influence decisions about the appropriate QC frequency for a test method: 1.The reliability of the test method; 2.The expected length of time between reporting a patient result and its being acted on; 3.The likelihood that an erroneous reported patient result will lead to an inappropriate medical decision or action; and 4.The expected severity of patient harm if an inappropriate decision or action occurs. [...]patient risk not only depends on the likelihood of producing erroneous results when the test method is performing in its stable in-control state, but also on the increased likelihood of producing erroneous results when test methods are out-of-control. [...]knowing how often a test method goes out-of-control (the reliability of the test method) is an important consideration when assessing an appropriate frequency for QC testing in order to adequately manage overall patient risk. Some analytes are critical to the medical decisions and actions taken; others are peripheral. [...]for some analytes it is much more likely that an erroneous reported patient result will lead to inappropriate decisions or actions.