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[PLATELETS FUNCTION IN A DROP OF BLOOD: FLOW CYTOMETRY ANALYSIS COMPARED TO PLATELET AGGREGATION].

INTRODUCTION
Light transmission aggregometry (LTA) is the most commonly used test for the diagnosis of platelet function disorders, but requires large amounts of blood samples and normal platelet count.


OBJECTIVES
To compare flow cytometric (FC) platelet function testing to standard LTA in the general population, in patients treated with anti-platelets drugs and in term and preterm neonates.


METHODS
Platelet function was assessed with LTA and FC using PAC1 binding and p-selectin expression, as platelet activation markers, in response to agonist activation. A comparison between LTA and FC was performed in a Clopidogrel treated patient, before and after (24 and 72 hours) loading the drug. The platelet activation markers PAC1 and p-selectin, were compared in umbilical cord blood samples of in-term and preterm neonates.


RESULTS
ADP-induced platelet aggregation was comparable to p-selectin expression assayed by FC (r=0.79-0.86) as measured before and after Clopidogrel loading. Both tests showed good response to Clopidogrel in 72 hours but not in 24 hours after its loading. Preterm cord blood platelets showed decreased ADP-induced activation in both activation markers: PAC1 and p-selectin, but only p-selectin reached statistical significance. We identified possible platelet activation markers in response to commonly used agonists' stimulation for FC analysis.


CONCLUSIONS
FC analysis of platelet function has added value in the diagnosis of impaired platelet function and anti-platelet drug response. Using FC enables us to test platelet function in minimal blood volume and regardless of platelet count. Identification of the unique activation marker for each agonist is prerequisite for FC analysis of platelet function.