Abstract-Text (inkl. Referenzen und Bildunterschriften)

Background

The clinical course of ischemic and hemorrhagic strokes can be influenced by the coagulation status of individual patients. The prior use of antiplatelet agents such as acetylsalicylic acid (ASA) or P2Y12-antagonists has been inconsistently described as possibly increasing the risk of hemorrhagic transformation or expansion. Since clinical studies describing prior use of antiplatelet medication are overwhelmingly lacking specific functional tests, we aimed to implement testing in routine stroke care.

Methods

We used fluorescence-activated cell sorting (FACS) with antibodies against CD61 for thrombocyte identification and CD62p or PAC-1 to determine platelet activation. Light-transmission aggregometry (LTA) and automated platelet functioning analyzer (PFA-200) were employed to test thrombocyte reactivity. FACS and LTA samples were stimulated in vitro with arachidonic acid (AA) and adenosine disphosphate (ADP) to measure increase in CD62p-/PAC-1-expression or aggregation, respectively.

Results

Between February and July 2023, 20 blood samples (n= 11 ischemic strokes; n= 7 hemorrhagic strokes; n= 2 controls) were acquired and analyzed within 24h of symptom onset. N=11 patients had taken ASA, n=8 patients no antithrombotic medication and n=1 ASA+clopidogrel. ASA compared to no antithrombotic medication was associated with lower CD62p expression after stimulation with AA on FACS analysis (median 15.8%; [interquartile range {IQR} 12.6%-37.2%] vs. 40.1% [IQR 20.3%-56.3%]; p=0.020), lower platelet aggregation (9.0%; [IQR 7.0%-12.0%] vs. 88.5% [IQR 11.8%-92.0%]; p=0.015) and longer time to plug formation with PFA (248.0 sec [IQR 157.0-297 sec] vs 121.5 sec [IQR 99.8-174.3]; p=0.027). Significant correlations were noted between AA-induced CD62p expression and aggregometry (n=18; ρ=0.732; p<0.001) as well as a negative correlation between CD62p increase and PFA clot formation time (n=18; ρ= -0.564; p=0.015). Sensitivity for ASA intake was highest for PFA (81.8% with values ≥ 155.5 sec). The combination of ASA+clopidogrel also affected ADP-induced CD62p and PAC-1 expression.

Conclusion

In the clinical setting it is feasible to use differentiated platelet analytics to determine alterations caused by antithrombotic medication. Among the tests under investigation, PFA showed the highest sensitivity for the intake of ASA in stroke patients. FACS analysis on the other hand might be able to provide a more nuanced approach to altered platelet reactivity.