For PTT samples when GT is not indicated (non GT), how long are they good?

For PTT samples when GT is not indicated (non GT), how long are they good?

• A. 1 hour
• B. 8 hours
• C. 24 hours
• D. 48 hours

Answer: (A)

The key idea is pre-analytical stability for PTT testing. When a gel separator is not used (non GT), the plasma remains in contact with the blood cells after collection, and ongoing cellular metabolism can alter coagulation factors and inhibitors. This makes the result unreliable if the specimen sits around too long. Because of that, PTT samples without a gel barrier are considered good for only a short window—about one hour at room temperature—before testing is required. The presence of a gel separator helps preserve stability and can extend the acceptable hold time, but without it you should plan to run the test promptly.

The key idea is pre-analytical stability for PTT testing. When a gel separator is not used (non GT), the plasma remains in contact with the blood cells after collection, and ongoing cellular metabolism can alter coagulation factors and inhibitors. This makes the result unreliable if the specimen sits around too long. Because of that, PTT samples without a gel barrier are considered good for only a short window—about one hour at room temperature—before testing is required. The presence of a gel separator helps preserve stability and can extend the acceptable hold time, but without it you should plan to run the test promptly.