Congress of the International Society on Thrombosis and Haemostasis

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Assessment of responsiveness to antiplatelet therapy by light transmittance aggregometry: an adjustment for platelet count is not necessary

Abstract number: PP-MO-730

Schwonberg¹ J., Linnemann¹ B., Prochnow¹ S., Mani¹ H., Lindhoff-Last¹ E.

¹¹Division of Vascular Medicine – Department of Internal Medicine, J.W.Goethe University Hospital, Frankfurt am Main, Germany

How-to-cite Schwonberg J, Linnemann B, Prochnow S, Mani H, Lindhoff-Last E. Assessment of responsiveness to antiplatelet therapy by light transmittance aggregometry: an adjustment for platelet count is not necessary. Journal of Thrombosis and Haemostasis 2009; Volume 7, Supplement 2: Abstract PP-MO-730

Background: Until now, light transmittance aggregometry (LTA) is considered to be the ‘gold standard’ to monitor antiplatelet therapy and to identify patients with non-responsiveness to either aspirin or clopidogrel. Because aggregometry has yet been poorly standardized, we aimed to analyze the results of LTA in healthy subjects and patients with antithrombotic medication using different concentrations of agonists and performing tests in non-adjusted and platelet count-adjusted platelet rich plasma (PRP).

Methods: LTA was performed in 20 healthy subjects and in patients treated with aspirin (n = 30) or clopidogrel (n = 30) monotherapy as well as in patients on combination therapy (n = 20) using arachidonic acid (ARA 250 and 500 mg/L) and adenosine diphosphate (ADP 2 and 5 μM) as agonists and performing platelet function tests in non-adjusted and platelet count (250/nl ± 10%)-adjusted PRP on the fully automated Behring Coagulation Timer^¯ (BCT).

Results: The overall platelet aggregation response is decreased after adjusting the PRP for platelet count compared to measurements in unadjusted PRP. The variability of aggregation results is high in adjusted PRP in the subgroup of healthy subjects, ranging from 9.2 to 95.3% (5th–95th percentile) relative to 77.6–95.5% in non-adjusted PRP when determining maximum aggregation with ARA 500 mg/L. Late aggregation using ADP 2 μM ranges from 3.8% to 89.9% in adjusted PRP compared to 42.9–92.5% in non-adjusted PRP. Maximum aggregation using ARA 500 mg/L in non-adjusted PRP differentiates well between aspirin-treated patients and healthy controls, whereas late aggregation using ADP 2 μM in non-adjusted PRP offers the best discrimination between clopidogrel-treated patients and healthy controls.

Conclusions: When using LTA for assessment of efficacy of antiplatelet therapy, an adjustment of PRP for platelet count does not provide any advantage and therefore the time consuming process of platelet count adjustment is not necessary.

Disclosure of interest: none declared.

To cite this abstract use the following format:

Journal of Thrombosis and Haemostasis 2007; Volume 5, Supplement 2: abstract number

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Session name:	ISTH2009
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