What condition is cause for rejecting an analytical run based on quality control?

The condition causing the rejection of an analytical run based on quality control is when two consecutive controls are more than 2 standard deviations (s) above or below the mean. This situation indicates that the analytical process is likely out of control, as such variation suggests a significant error or deviation from expected performance.

Quality control procedures rely on the statistical principles of normal distribution, where most data points should fall within 1 to 2 standard deviations of the mean. When controls exceed these limits, especially by 2 or more standard deviations, it raises concern regarding the reliability of the test results. This type of deviation implies that the system may have an issue, such as a reagent problem, instrument malfunction, or procedural error, warranting a thorough investigation and possibly a recalibration or rerun of the tests.

In contrast, conditions such as three consecutive controls above 1 s from the mean, four controls steadily increasing but still within ±1 s, or one control above +1 s and another below -1 s do not indicate a clear failure of the quality control process, as they may not represent a significant enough deviation to require rejection of the analytical run. These scenarios may indicate variability within acceptable limits or random error rather than systematic error, which is critical to identify