Stability of plasma for add-on PT and APTT tests

Area of Science:

• Clinical Chemistry
• Hematology
• Laboratory Medicine

Background:

• Prothrombin time (PT) and activated partial thromboplastin time (APTT) are crucial diagnostic tests.
• The stability of plasma for these tests after prolonged storage is a significant concern for laboratory efficiency and patient care.

Purpose of the Study:

• To determine the time limit for performing add-on PT and APTT tests on plasma stored with blood cells at room temperature.
• To assess if delayed testing yields clinically significant differences compared to immediate testing.

Main Methods:

• PT and APTT tests were performed on fresh plasma and plasma stored with blood cells at room temperature for 2, 4, and 8 hours.
• Samples were analyzed from healthy subjects, patients on warfarin, and patients on heparin therapy.

Main Results:

• Prothrombin time (PT) values showed minor, clinically insignificant decreases in most healthy and warfarin-treated patients upon storage.
• Activated partial thromboplastin time (APTT) values in healthy subjects generally increased slightly with storage, within acceptable limits.
• APTT differences in heparinized patients were larger but within acceptable ranges for duplicate testing, with no clear time-dependent trend.

Conclusions:

• Add-on PT and APTT tests can be reliably performed on plasma stored with spun-down cells at room temperature for up to 8 hours.
• Delayed testing yields results comparable to immediate testing, offering flexibility in laboratory workflows.