QC protocols prohibit the use of outdated evacuated tubes because why?

The rationale behind prohibiting the use of outdated evacuated tubes primarily revolves around the potential for incomplete filling of the tube, which can lead to altered additive-to-sample ratios. Each evacuated tube is designed with a specific vacuum level, which ensures that when a sample is drawn, the correct volume of blood is collected in relation to the additives present in the tube.

As tubes age, especially beyond their expiration date, the vacuum may diminish or fail altogether, resulting in insufficient sample volume. This not only compromises the quality of the sample but also affects the accuracy of the test results, as the proportion of blood to the chemical additives may be skewed. Incorrect ratios can lead to inaccurate test outcomes, thus affecting patient diagnosis and treatment decisions.

This concern highlights the importance of adhering to quality control (QC) protocols that dictate the use of tubes within their specified shelf life to ensure reliability and safety in laboratory testing.