Role of the laboratory in monitoring patients receiving dual antiplatelet therapy

Introduction: The increasing demand for therapeutic monitoring in patients receiving antiplatelet therapy has been paralleled by the development of instruments and tests whose clinical usefulness is still under debate. We devised a laboratory approach to detect patients with antiplatelet resistance at risk to develop thrombotic events. Methods: One hundred and eighty patients, under aspirin and clopidogrel after angioplasty and stent implantation, were studied by PFA100^® with collagen/epinephrine (CoEPI, cutoff 165s) cartridge and by Multiplate^® using arachidonic acid (ASPItest, pos<862AUC), ADP (ADPtest, pos<417AUC), and collagen (COLtest, pos<607AUC). Results: Only 67 of 173 patients with ASPI<862 displayed a prolonged CoEPI and up to 65 patients had normal CoEPI despite ASPI<300. Patients with ASPI<300 had significantly lower COL than patients with ASPI>300. One hundred and thirty-eight patients displaying ADP<417 had significantly lower COL than those with ADP>417. Association between COL and ADP remained after ASPI stratification: in patients with suboptimal (ASPI 300-892) or maximal (ASPI<300) response to aspirin, having ADP<417 (clopidogrel responsive) increased COL positivity, respectively, from 9.5 to 58.8% and from 47.6 to 82.7%. Conclusion: A combination of specific tests may be useful in identifying higher-risk patients with poor compliance or drug resistance who potentially may benefit from therapy change.