Which of the following is an example of a preanalytic error that can lead to falsely prolonged coagulation test results?

• A. Insufficient blood volume in the collection tube
• B. Hemolyzed sample
• C. Delayed processing
• D. All of the above

Answer: (A)

Preanalytic factors are changes to the specimen before testing that can distort coagulation results. In coagulation testing, the blood-to-anticoagulant ratio must be precise. If the tube is under-filled, there is too much citrate relative to blood, which binds calcium more than intended and slows clot formation, producing falsely prolonged PT and aPTT.

A hemolyzed sample introduces substances from ruptured red cells that can interfere with reagents and the clot-detection process, leading to unreliable results that are often prolonged.

Delayed processing allows clotting factors to degrade or be consumed while the sample sits, or for the sample to begin clotting in the tube, both of which can extend the measured clotting times.

Because each of these scenarios can independently cause falsely prolonged coagulation results, the best choice is that all of the above are preanalytic errors that can lead to this issue.