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Platelet Aggregation Testing by Light Transmission Aggregometry with Drug Specific Agonists in Patients on Mono and Dual Antiplatelet Therapy

Background: Recently, platelet function testing is increasingly included in assessment of the effectiveness of antiplatelet therapy in research and clinical settings. Literature data suggest high residual platelet reactivity measured by light transmission aggregometry (LTA) as >20% when induced with arachidonic acid (AA) and >70% when induced with adenosine diphosphate (ADP). Aims: To evaluate platelet reactivity by LTA using drug specific agonists in patients on long-term mono and dual antiplatelet therapy. Methods: Study included 191 consecutive patients on dual antiplatelet therapy, 158 patients on monotherapy with acetylsalicylic acid (ASA) and 37 on clopidogrel referred to our laboratory for platelet aggregation testing. Platelet rich plasma was obtained from 3.2% citrate plasma centrifuged at 500xg/10 minutes. LTA was done on Sysmex CS2500 (Siemens Healthineers, Germany) using AA (1 mmol/L) and ADP (2 µmol/L) as agonists (Hyphen Biomed, France). Parametric and nonparametric analysis of variance was used to test the differences between studied groups. Results: Among 191 patients with median age 64 yrs (range 26-90) on dual therapy, 170 were using clopidogrel (75 mg) and ASA (100 mg) whereas 21 were using ticagrelor (90 mg) and ASA (100 mg). Results for AA were 7% (interquartile range (IQR) 3-10)) and for ADP 35%±17%, respectively. Group of patients using ticagrelor and ASA has significantly lower ADP results than those using clopidogrel and ASA (median 20% ; IQR 16-27) vs median 37% ; IQR 23- 49 ; P< 0.001). Patients on ASA monotherapy (N=158) had AA 9% (IQR 4-16) while in those on clopidogrel therapy (N=37), aggregation with ADP agonist was 68%±10%. Only 8 (4%) patients on dual therapy did not reach suggested cut-off for AA in contrary to 20 (13%) patients on monotherapy with ASA (Table 1). Conclusions: Our study has shown that a higher proportion of patients on long term ASA monotherapy has high residual platelet reactivity compared to patients on dual antiplatelet therapy.

antiplatelet therapy, light transmission aggregometry

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