Why might a laboratory reject a specimen for INR testing?

A laboratory might reject a specimen for INR testing if it has been delayed in transit for an extended period, such as 6 hours. INR testing, which assesses blood coagulation and is crucial for managing conditions like anticoagulation therapy, requires that specimens be handled properly to maintain their integrity.

Prolonged delays in transit can lead to degradation of the sample components, affecting the accuracy of the INR results. Specifically, factors in the blood can undergo changes that might produce misleading results, which could potentially lead to inappropriate clinical decisions. Timely processing is essential for preserving the test's reliability, making a 6-hour delay a critical factor in specimen rejection.

In contrast, the other scenarios typically do not lead to automatic rejection. For instance, spinning down a sample for 10 minutes is a standard practice that helps to separate the serum or plasma from the cells for testing. Refrigerating a sample for 1 hour is generally acceptable and can help to preserve the sample’s integrity while awaiting analysis. Lastly, a specimen filled three-quarters full is usually acceptable, as long as it is within the laboratory's specified volume requirements, which often allow for slight under-filling.