A phlebotomy technician is asked to retrieve a specimen for a coagulation study (PT/INR) that was collected 6 hours ago and has been stored at room temperature. What is the most likely impact on the test results?
- AThe specimen will be hemolyzed, making it unsuitable for testing.
- BThe PT/INR results will be falsely increased.
- CThe PT/INR results will be falsely decreased.
- DThe specimen will be acceptable as coagulation factors are stable at room temperature for extended periods.
Show answer & explanationAnswer & explanation
Correct answer: B. The PT/INR results will be falsely increased.
Coagulation specimens (e.g., for PT/INR) collected in light-blue top tubes (sodium citrate) are stable for a limited time at room temperature, typically up to 24 hours if plasma is separated within 1 hour. If whole blood remains unspun for too long (e.g., 6 hours), coagulation factors can begin to degrade or be activated, leading to falsely prolonged (increased) PT/INR results. For PT/INR, plasma should ideally be separated within 1-2 hours.
Why the other options are wrong
- A. Hemolysis is caused by physical trauma to red cells, not typically by extended room temperature storage of unspun blood in a citrate tube.
- C. Falsely decreased results are less likely; degradation or activation tends to prolong clotting times.
- D. Coagulation factors, especially factor V and VIII, are labile and degrade over time, making extended room temperature storage of unspun whole blood unacceptable for accurate results. Plasma separation is key for stability.
Coagulation Specimen Stability
Coagulation specimens (light-blue top) have specific stability requirements. Unspun whole blood should be processed (plasma separated) within a critical timeframe (e.g., 1-2 hours for PT/INR) at room temperature to prevent degradation of labile coagulation factors and ensure accurate results.
- Sodium citrate tube.
- Plasma separation critical for stability.
- Unspun whole blood stability is limited.
Memory trick: Coagulation: Time's the Foe, Factors Flee Slow.