PB0625 - Influence of centrifugation and residual platelet count on PAI-1 plasma level, euglobulin clot lysis time and global fibrinolytic capacity of plasma

Background: Coagulolytic assays with (i.e global fibrinolytic capacity of plasma (GFC)) or without exogenous fibrinolysis activator (i.e euglobulin clot lysis time (ECLT)) are often used as screening tools to explore fibrinolysis.

Pre-analytical conditions to obtain platelet-depleted plasma (PPP) suffer from a lack of standardization, especially about centrifugation.

Platelet α-granules have been described as a circulating pool of PAI-1, accounting for approximately 50 % of total circulating PAI-1 activity due to platelets abundance.

As ECLT and GFC are both sensitive to PAI-1 plasma level, residual platelets in PPP could be a source of PAI-1 which may interfere with GFC and ECLT results.

Aims: To study the influence of centrifugation scheme and residual platelet count on PAI-1 level, euglobulin clot lysis time and global fibrinolytic capacity of plasma.

Methods: The influence of centrifugation scheme was assessed with plasma samples from healthy volunteers.

The experimental design is summarized figure 1.

The study was approved by the Local Ethics Committee (NUB: B0392020000042).

Statistical analysis was performed in R, using one-way ANOVA for repeated measures or Friedman test as appropriate.

Results: Good correlation between PAI-1 plasma level and ECLT and GFC, with a Pearson coefficient of 0.63 (p < 0.0001) and 0.64 (p < 0.0001) respectively.

Residual platelet counts differed according to the centrifugation scheme (p < 0.0001, fig. 2.A), but not PAI-1 levels (p=0.75, fig. 2.B and 2.C) nor GFC (p=0.18) and ECLT (p=0.091).

Conclusion(s): Active PAI-1 plasma level showed a statistically highly significant (p < 0.0001) correlation with ECLT and GFC.

The centrifugation scheme, despite its expected influence on residual platelet count in plasma, does not seem to influence plasma PAI-1 level nor ECLT and GFC. This could be explained by the fact that platelet PAI-1 is less active than plasma PAI-1, and approximately 40% of total platelet-derived PAI-1 remains anchored to the platelet membrane through the αIIbβ3 integrin.