Rapid Platelet-Function Assay

Abstract

Background-The platelet glycoprotein (GP) IIb/IIIa receptor is important in mediating platelet thrombus formation, and the GP IIb/IIIa antagonist abciximab (c7E3 Fab; ReoPro) is effective in preventing thrombotic ischemic cardiovascular complications of unstable angina and percutaneous coronary interventions. Small-molecule antagonists of GP IIb/IIIa based on the Arg-Gly-Asp (RGD) sequence show similar benefit, and some of these agents are orally active. However, there may be significant interindividual variation in response to such antagonists, especially with chronic oral therapy. It will be essential to balance the beneficial antithrombotic effect of these drugs with their potential for causing bleeding. In response to this need, we have developed a rapid platelet-function assay (RPFA), a point-of-care system that provides a quantitative measure of the competence of the GP IIb/IIIa receptor as reflected in the ability of platelets to agglutinate fibrinogen-coated beads. Methods and Results-Polystyrene beads were coated with fibrinogen and placed in a cartridge along with a lyophilized peptide that activates the thrombin receptor. Anticoagulated whole blood was added to the cartridge, and then a microprocessor-controlled operation mixed the reagents and detected agglutination between platelets and coated beads.Quantitative digital results were displayed within 3 minutes. Because there is no dilution of the blood, the assay can be used to measure platelet activity in samples that have been treated with GP IIb/IIIa antagonists with high dissociation rates. RPFA results of whole-blood samples treated with different GP IIb/IIIa antagonists correlated well with both conventional turbidimetric platelet aggregation (r 2 ϭ0.95) and the percentage of free GP IIb/IIIa molecules in the sample (r 2 ϭ0.96). The mean difference in measurements between RPFA and aggregometry was -4% (Ϯ4% SD), and the mean difference in measurements between RPFA and free GP IIb/IIIa receptors was -2% (Ϯ6% SD). Conclusions-The

Testing Platelet Activation With a Shear-Dependent Platelet Function Test Versus Aggregation-Based Tests

“…Smith et al 6 reported results different from ours using the RPFA. Because the RPFA was marketed to assess platelet function after short-term administration of GP IIb/IIIa inhibitors, they mainly used high concentrations of abciximab.…”

Effects of aliskiren, a renin inhibitor, on biomarkers of platelet activity, coagulation and fibrinolysis in subjects with multiple risk factors for vascular disease

“…When the activated platelets are exposed to the fibrinogen-coated microparticles, agglutination occurs in proportion to the number of available platelet receptors. The whole blood-citrate mixture is being added to the cartridge, and agglutination between platelets and coated beads is being recorded, 15 and the results are reported as platelet activation units. The data mirror turbidometric platelet aggregation and reflect the degree of platelet activity.…”

Migration distance-based platelet function analysis in a microfluidic system

“…[10][11][12][13][14][15][16][17] Lighttransmission aggregometry has been widely used as the gold standard to identify and diagnose defects in platelet function. 12,13 However, it requires platelet-rich plasma, a time-consuming test procedure, and large sample volumes.…”

“…18,19 Meanwhile, VerifyNow (Accumetrics, San Diego, CA, USA) is a turbidimetric, point-of-care device based on integrin aIIbb3 (GPIIb/IIIa)-dependent platelet aggregation, which is augmented by the presence of fibrinogen-coated beads. 11,14 A shear-induced platelet function analyzer (PFA-100, Siemens, Germany) has been introduced. 10,[15][16][17] This device lets anti-coagulated whole blood flow through a narrow hole (d ¼ 150 lm) punched in membranes coated with collagen and either ADP or epinephrine.…”