Evaluation of the platelet count drop method for assessment of platelet function in comparison with "gold standard" light transmission aggregometry (original) (raw)
Related papers
2007
Background: Two point-of-care (POC) systems have been recently proposed as rapid tools with which to evaluate residual platelet reactivity (RPR) in coronary artery disease (CAD) patients. Objectives and Methods: We compared Platelet Function Analyzer-100 (PFA-100) closure times (CTs) by collagen/adenosine 5´-diphosphate (ADP) (C/ADP CT) cartridge and the VerifyNow P2Y12 Assay (VerifyNow) with light transmission aggregation (LTA) induced by 2 and 10 lmol L-1 ADP in 1267 CAD patients on dual antiplatelet therapy who underwent percutaneous coronary intervention. We also performed the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay by cytofluorimetric analysis in a subgroup of 115 patients. Results: Cutoff values for identifying RPR were: ‡ 54% and ‡ 66% for LTA induced by 2 and 10 lmol L-1 ADP respectively, and ‡ 264 P2Y12 Reaction Units (PRU) for VerifyNow. The cutoff for PFA-100 C/ADP CT was ‡ 68 s. RPR was detected in 25.1% of patients by 2 lmol L-1 ADP-induced LTA (ADP-LTA), in 23.2% by 10 lmol L-1 ADP-LTA, in 24.4% by PFA-100, and in 24.7% by VerifyNow. PFA-100 results did not parallel those obtained with LTA. VerifyNow showed a significant correlation (q = 0.62, P < 0.001) and significant agreement (k = 0.34, P < 0.001) with LTA induced by 2 lmol L-1 ADP. The correlation was similar but the agreement was better between VerifyNow and 10 lmol L-1 ADP-LTA (q = 0.64, P < 0.0001; k = 0.43, P < 0.001). Significant relationships were found between VASP platelet reactivity index and both ADP-LTA and VerifyNow. PFA-100 C/ADP CT did not significantly correlate with any of the other assays. Conclusions: Our results show a significant correlation between LTA and VerifyNow but not the PFA-100 C/ADP assay. Clinical validation studies for POC systems are necessary.
Platelets, 2005
Recent studies suggest that anti-platelet agents are not equally effective in all individuals. We have developed a new method to evaluate the effect of anti-platelet drugs using the cone and plate(let) analyzer (CPA) test. The method is based on the ability of activators to reduce platelet adhesion under flow conditions. Treatment of a blood sample with arachidonic acid (AA) or ADP in vitro significantly decreased platelet deposition to a surface coverage (SC) of 2.1+/-0.4 and 1.3+/-0.6%, respectively, compared with the basic SC of 12.3+/-6.8%. The effect of AA was prevented by aspirin (SC 8.1+/-3.8%) and that of ADP was reduced by 2-methylthio-AMP, a P2Y12 ADP receptor inhibitor (SC 4.8+/-2.0%). Pre-incubation with AA of whole blood samples from untreated healthy volunteers resulted in a marked decline of SC (from SC 9.8+/-2.2 to 0.6+/-0.3%). In contrast, in volunteers treated with 100, 300, and 500 mg aspirin per day, AA (but not ADP) decreased SC only to 3.5+/-1.3, 4.4+/-1.7, and 4.1+/-2.0%, respectively (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001 versus SC with AA before treatment). A good correlation was observed between the modified CPA and aggregometry (R2=0.55). In conclusion, the modified CPA test is a useful tool to evaluate the efficacy of anti-platelet therapy.
Thrombosis …, 2010
Objectives: Evaluation of aspirin (ASA) responsiveness with platelet function tests varies by the choice of blood mixture and functional test and cut off values for defining the the treatment used. Addition to that we also aimed to determine aggregement between three tests and to research whether there is any necessity to measure baseline platelet activity. Methods: The study group comprised of 52 patients with multiple risk factors receiving primary prophylaxis of ASA (100 mg/day). For each patient inhibition of platelet aggregation with aspirin was determined using three different whole blood tests: Multiplate electrical impedance aggregometry , Verify Now Aspirin, and collagenepinephrine closure time PFA-100. Platelet aggregation was assessed with multiplate electrical impedance aggregometry,and was defined as the area under curve (AUC,AUxmin).Maximal 6,4 microM collagen-induced AUC were used to quantify platelet aggregation due to ASA.The ASA response was defined as > 30 % reduction in basal platelet aggregation with multiplate electrical impedance aggregometry.Collagen induced platelet aggregation at the Verify Now Aspirin assay quantitated the ASA-induced platelet inhibition as aspirin reaction units (ARU).According to manifacturer insert ARU > 550 indicates aspirin resistance. ASA platelet function studies were assessed twice at baseline (pre-aspirin), and after 7 day(post-aspirin) were performed. Results: After ASA intake none of the patients was found aspirin resistant with PFA-100. (CEPI-CT (129 ± 36 vs 289 ± 18). None of the patients was found aspirin resistant with PFA-100. As > 30 % reduction in bazal platelet aggregation with multiplate electrical impedance aggregometry is selected all of the patients have been stratified as responders.(COL TEST 688±230 vs 169 ± 131 AU) None of the patients with Verify Now Aspirin found resistance to ASA(594 ± 62 vs 446 ± 43).Prior to ASA intake 15 of all patients with VN(501 ± 16) and 2 of all patients with multiplate electrical impedance aggregometry (223 ± 40 AUC)aggregation levels below the cut off label before ingestion of ASA.None of the patients was above the cut off label with PFA-100 (129 ± 36). Conclusions: Verify Now ASA assay, multiplate electrical impedance aggregometry and PFA-100 seem to be reliable tests in reflecting ASA effect on platelets. Cut off labels for the defining the responsiveness given by manıfacturer may show significant interindividual variabiliy with Verify Now ASA assay and multiplate electrical impedance aggregometry, and these test may show platelet inhibition despite the absence of ASA intake. Consideration of the pretreatment values may eliminate the risk of overestimation in the assessment of platelet inhibtion by ASA.
Scandinavian journal of clinical and laboratory investigation, 2017
Dual antiplatelet therapy with clopidogrel is a regimen used before and after drug-eluting stent (DES) implantation. Point-of-care platelet reactivity assays are easy-to-use methods to determine adequate response to the drug. The aim of this study was a comparison of the two platelet reactivity assays: Multiplate(®) and VerifyNow(®) and an identification of factors potentially influencing the results of these tests, including common genetic polymorphisms. The study included 39 patients receiving 75 mg clopidogrel daily before angioplasty with DES implantation. Platelet reactivity was measured with Multiplate and P2Y12 VerifyNow assays. Genetic polymorphisms of CYP2C19*2, ABCB1 3435C > T, and CYP3A4*1G were determined with PCR-RFLP method and CYP2C19*17 was determined by means of an allele-specific PCR. Agreement between Multiplate and VerifyNow assays was poor (Cohen's κ = 0.056, p = .273). Hematocrit significantly negatively correlated with VerifyNow assayed platelet reactiv...
Platelet Aggregometry Testing: Molecular Mechanisms, Techniques and Clinical Implications
International Journal of Molecular Sciences, 2017
Platelets play a fundamental role in normal hemostasis, while their inherited or acquired dysfunctions are involved in a variety of bleeding disorders or thrombotic events. Several laboratory methodologies or point-of-care testing methods are currently available for clinical and experimental settings. These methods describe different aspects of platelet function based on platelet aggregation, platelet adhesion, the viscoelastic properties during clot formation, the evaluation of thromboxane metabolism or certain flow cytometry techniques. Platelet aggregometry is applied in different clinical settings as monitoring response to antiplatelet therapies, the assessment of perioperative bleeding risk, the diagnosis of inherited bleeding disorders or in transfusion medicine. The rationale for platelet function-driven antiplatelet therapy was based on the result of several studies on patients undergoing percutaneous coronary intervention (PCI), where an association between high platelet reactivity despite P2Y12 inhibition and ischemic events as stent thrombosis or cardiovascular death was found. However, recent large scale randomized, controlled trials have consistently failed to demonstrate a benefit of personalised antiplatelet therapy based on platelet function testing.
Haematologica, 2010
Assays to evaluate platelet function are often interchangeably used to assess "resistance" to aspirin. We compared different platelet function assays in patients treated or untreated with aspirin. Design and Methods Platelet function was evaluated in 162 subjects, 85 of whom were not being treated with any antiplatelet drug and 77 of whom were receiving chronic therapy with low-dose aspirin. Platelet Function Analyzer collagen/ADP-and collagen/epinephrine closure times, as well as light transmittance aggregometry in response to ADP, collagen and arachidonic acid (this last in 47 aspirin-treated patients) were determined. In 43 aspirin-treated patients, serum thromboxane B2 levels were also measured. Results In untreated patients, collagen/ADP-and collagen/epinephrine-closure times were correlated with each other (r=0.5, P=0.0001), but did not correlate with ADP-or collagen-induced aggregation. In patients treated with aspirin, collagen/ADP-closure time values were not different from those in untreated patients, while the collagen/epinephrine-closure time was prolonged. ADP-induced aggregation was unaffected by aspirin, while collagen-induced aggregation was reduced. Arachidonic acid-induced aggregation was almost completely suppressed (% maximum light transmittance aggregometry=5±13%). There was, however, no correlation between the various platelet function tests. Serum thromboxane B2, an index of platelet cyclooxygenase-1 activity, was almost completely suppressed (down to 8±17 ng/mL) in treated patients, and was not correlated with arachidonic acid-, ADP-and collagen-induced aggregation or with collagen/ADP-closure time, but was inversely correlated with collagen/epinephrine-closure time. Conclusions There is a high heterogeneity of results of tests evaluating inhibition of platelet function by aspirin, and the results of functional tests do not match biochemical measurement of cyclooxygenase-1 activity. Extreme caution should, therefore, be used in defining "resistance" to aspirin on the basis of the results of these tests.