When performing quality control checks, tubes should be discarded under which circumstance?

When performing quality control checks, a tube with small cracks in the stopper should be discarded because the integrity of the stopper is crucial for maintaining the sterility and proper vacuum of the tube. Cracks can compromise the seal, leading to potential contamination or loss of vacuum, which can significantly affect test results. A tube that does not maintain a proper vacuum may not draw the correct volume of blood, and any contaminants that enter through the cracks can alter the sample's composition, leading to inaccurate laboratory findings. Ensuring that all tubes are in pristine condition, especially the stoppers, is vital for reliable diagnostic results.