Which QC issue occurs when six consecutive results are on the same side of the mean?

The scenario described involves six consecutive results consistently falling on the same side of the mean, which indicates a systematic deviation from the expected value. This situation is classified as a shift in quality control (QC). A shift represents a sudden and consistent change in the measurement outcome, suggesting that something has altered in the testing process or environment that affects the results, leading them to cluster away from the average value.

In a shift, the data points are likely to stray in one direction, either above or below the mean, indicating a persistent and systematic error rather than random variation. This kind of QC issue often prompts investigation into potential problems with the assay, calibrators, reagents, or equipment used, as it suggests a failure in the reliability of the testing method.

Understanding shifts is critical in laboratory QC, as they can impact the accuracy of test results and may lead to incorrect clinical decisions if undetected. Thus, recognizing and addressing shifts promptly ensures the integrity of laboratory findings.