Which factor can lead to a trend in quality control results?

Deterioration of reagents is a significant factor that can lead to a noticeable trend in quality control results. Over time, reagents used in clinical chemistry can lose potency, become contaminated, or undergo degradation due to factors like temperature fluctuations or prolonged storage. When reagents deteriorate, they may not perform as expected, leading to consistent deviations from the established quality control limits. This can manifest as a systematic shift in the test results, creating a trend that may not correlate with the actual patient samples being tested.

In contrast, changes in average test results may indicate a shift but not necessarily a trend caused by a specific factor. Random fluctuations are expected in any measurement system and do not indicate a systematic issue. Operator error, while it can certainly affect test results, often leads to sporadic errors rather than a consistent trend. Therefore, the impact of reagent quality is critical to maintaining reliable and accurate quality control tracking over time.