Samples for PT and Factors II, V, VII, and X (n=4) were tested immediately post collection, then every 2 hours until 8 hours, and again at 24 hours. Samples for PT and Factor VII were also analysed at 48 hours (Figure 1).
Results for Factor VII significantly increased (p<0.01) between 2-8 hours post collection, exceeding 10% at 6 hours. This increase in Factor VII could be due to cold activation, which is well documented [1]. From 24 hours, Factor VII levels began to drop, presumably due to consumption, reaching -2.9% from baseline at 48 hours, and were no longer deemed significantly different (Figure 1A). It would appear that Factor VII is mainly responsible for PT stability, which showed an opposite trend. PT results initially decreased between 2- 6 hours post collection and subsequently increased from 8 hours onward. Although PT results were deemed significantly different between 4-8 hours post collection, they never exceeded 10% from baseline within 48 hours.
Factors II, V, and X did not exceed 10% difference from baseline within 24 hours (Figure 1B). However, results were deemed significantly different at 8 hours for factor II (p<0.01) and 24 hours for factors V (p<0.01) and X (p=0.02).
References
- Seligsohn U, Zivelin A, Bar-Shani S. Cold Promoted Activation of Factor VII: Is it a Problem Under Blood Bank Conditions? Haemostasis. 1983; 13(3): 186-191