Serum uric acid levels during dual antiplatelet therapy with ticagrelor or clopidogrel: Results from a single-centre study.

BACKGROUND AND AIMS: New antithrombotic therapies have significantly improved the outcomes of patients with acute coronary syndrome (ACS), where the introduction of ticagrelor has provided the greatest mortality benefits. However, ticagrelor treatment has been associated with a potential increase in the serum uric acid (SUA) levels, which may influence endothelial dysfunction and prothrombotic status, thereby affecting the risk of acute cardiovascular events in patients requiring dual antiplatelet therapy (DAPT). The present study aimed to compare the impact of antiplatelet agents such as ticagrelor or clopidogrel on SUA levels and their effect on platelet reactivity. METHODS AND RESULTS: We included patients admitted for ACS or elective percutaneous coronary intervention (PCI) and discharged with ASA (acetylsalicylic acid; 100-160 mg) and clopidogrel (75 mg) or ticagrelor (90 mg twice a day). Chemistry was assessed at admission (baseline) and after a 30-90-day period of DAPT (together with platelet reactivity). The absolute and percentage variations of SUA after DAPT introduction were considered. Multiple-electrode aggregometry was used to assess platelet function. A total of 378 patients were enrolled, with 145 treated with aspirin and clopidogrel (AC) and 233 with aspirin and ticagrelor (AT). The AC patients were older (p = 0.003) and more often showed elective PCI as an indication to DAPT (<0.001); they received chronic therapy with ARB (angiotensin II receptor blocker; p = 0.001), nitrates (p = 0.044), CCB (calcium channel blocker; p = 0.005) and diuretics (p = 0.044). The AT patients displayed a higher percentage of ACS diagnosis (p < 0.001) and received chronic therapy with ACE (angiotensin-converting enzyme) inhibitors (p = 0.001), beta blockers (p = 0.001) and statins (p = 0.013). The AC patients displayed higher platelet reactivity at COL (collagen) test, ASPI test and ADP (adenosine diphosphate) test (p = 0.03, 0.001 and <0.001, respectively) and a higher percentage of HRPR (high residual platelet reactivity) in the ADP test (p = 0.001). No difference was found in the baseline uric acid and creatinine levels between AC and AT patients. At 30-90 days, a significant absolute and percentage increase in the SUA levels was found in AT as compared to AC patients (0.204 mg/dl vs. -0.165 mg/dl, p = 0.034; 6.26% vs. -0.005%, p = 0.018, respectively). Results were not influenced by variations in renal function. At multivariate analysis, in fact, ticagrelor therapy emerged as an independent predictor of increase in the uric acid levels (odds ratio (OR; 95% confidence interval (CI)) = 2.79 (1.66-4.67), p < 0.001). However, the variation in the SUA levels did not affect platelet reactivity or HRPR in both AC and AT patients. CONCLUSION: An increase in the SUA levels at 30-90 days was observed in patients receiving chronic DAPT with ticagrelor, but not clopidogrel treatment. However, the changes in the SUA levels do not influence platelet aggregation.

Uric acid and high-residual platelet reactivity in patients treated with clopidogrel or ticagrelor.

BACKGROUND AND AIM: High residual platelet reactivity (HRPR) is still an important challenge, despite the advent of new potent ADP-antagonists. Therefore it is of extreme importance to identify factors that can influence platelet activation. Serum uric acid (SUA) has been largely addressed in the past as a possible risk factor for coronary artery disease, with a possible association with platelets hyperreactivity. So far no studies have assessed the role of serum uric acid on the response to dual antiplatelet therapy. Therefore, the aim of our study was to evaluate the impact of uric acid levels on platelet function in patients treated with dual antiplatelet therapy (DAPT) with clopidogrel or ticagrelor. METHODS AND RESULTS: We scheduled for platelet function assessment at 30-90 days post-discharge patients treated with DAPT (ASA + clopidogrel or ticagrelor) for an ACS or elective percutaneous coronary intervention (PCI). Platelet function was assessed by whole blood impedance aggregometry (Multiplate(®)-Roche Diagnostics AG), HRPR was considered for ASPI test >862 AU(∗)min (for ASA) and ADP test values ≥417 AU* min (for ADP-antagonists). RESULTS: We included a total of 493 patients (262 were on ASA and clopidogrel and 231 on ASA and ticagrelor). Patients were divided according to quartiles of serum uric acid levels measured at the time of platelet aggregation assessment (Group 1 <4.6 mg/dL, n = 114; Group 2, 4.7-5.8 mg/dL, n = 133; Group 3, 5.9-6.8 mg/dL, n = 124; Group 4, >6.9, n = 122). Patients with higher uric acid levels were older, more often smokers, with history of hypertension and previous coronary artery bypass surgery and renal failure and were more often on therapy with diuretics at admission. Patients with higher SUA had higher triglycerides and fibrinogen. Uric acid levels did not influence ASPI, COL, TRAP and ADP tests. High residual platelet reactivity (HRPR) was observed in 1.5% of patients treated with ASA, with no difference according to SUA quartiles (p = 0.60), confirmed at multivariate analysis after correction for baseline confounders (adjusted OR[95%CI] = 1.05 [0.44-2.52], p = 0.90). HRPR for ADP-antagonists was observed in 23.6% of patients, with no difference according to SUA quartiles (p = 0.47); this result was confirmed also after correction for baseline confounders (adjusted OR[95%CI] = 1.04 [0.84-1.28], p = 0.73). Moreover, no association was found between HRPR and uric acid levels both among patients treated with clopidogrel (p = 0.35) or ticagrelor (p = 0.74), that was confirmed after correction for baseline confounding factors (adjusted OR[95%CI] = 1.18 [0.90-1.55], p = 0.23) and (adjusted OR[95%CI] = 0.96 [0.63-1.47], p = 0.85). The absence of association between SUA and platelet reactivity was confirmed at linear regression analysis both with clopidogrel (r = 0.03, p = 0.55) or ticagrelor (r = -0.01, p = 0.85). CONCLUSION: This is the first large study showing that in patients receiving DAPT, uric acid levels do not influence response to ticagrelor and clopidogrel or the effectiveness of ASA.

Advanced age and high-residual platelet reactivity in patients receiving dual antiplatelet therapy with clopidogrel or ticagrelor.

UNLABELLED: ESSENTIALS: Dual antiplatelet therapy (DAPT) in elderly patients requires balancing bleedings and thrombosis. Impact of age on high residual on-treatment platelet reactivity (HRPR) on DAPT was studied. A reduced effectiveness of adenosine diphosphate antagonists was observed over 70 years of age. The occurrence of HRPR was increased among elderly patients with both clopidogrel and ticagrelor. BACKGROUND: The aim of the present study was to evaluate the impact of age on platelet function and the occurrence of high residual on-treatment platelet reactivity (HRPR) in patients treated with dual antiplatelet therapy (DAPT) using acetylsalicilic acid (ASA) and clopidogrel or ticagrelor. METHODS: Patients treated with DAPT (ASA and clopidogrel or ticagrelor) were scheduled for platelet function assessment at 30-90 days post-discharge. By whole blood impedance aggregometry, HRPR was considered for ASPI test values > 862 AU*min (for ASA) and adenosine diphosphate (ADP) test values > 417 AU*min (for ADP antagonists). Elderly patients were defined as those aged ≥ 70 years. RESULTS: Among 494 patients on DAPT, 224 (45.3%) were ≥ 70 years old. ADP-mediated platelet aggregation increased with decades of age (279.3 ± 148.6 vs. 319.6 ± 171.1 vs. 347.3 ± 190.1 vs. 345.7 ± 169.2), whereas no difference was observed for ASA response. A reduced effectiveness of ADP antagonists was observed among elderly patients; in fact, among the 117 patients displaying HRPR (23.7%), a higher prevalence was observed among patients over 70 years old (30.4% vs. 18.1%; adjusted odds ratio (OR) [95% confidence interval (CI)] = 2.19 [1.29-3.71]). Similar results were obtained among the 266 clopidogrel-treated patients (38.5% vs. 27.9%; adjusted OR [95% CI] = 2.91 [1.46-5.8]) and in the 228 patients receiving ticagrelor (19.1% vs. 8.1%; adjusted OR [95% CI] = 2.55 [1.02-8.59]). CONCLUSION: In patients receiving dual antiplatelet therapy, advanced age is independently associated with a reduced effectiveness of ADP antagonists and a higher rate of HRPR with both clopidogrel and ticagrelor.

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.

Antibodies against oxidized phospholipids in laboratory tests exploring lupus anti-coagulant activity.

Lupus anti-coagulants (LA) are a variety of anti-phospholipid antibodies characterized by their capacity to interfere with phospholipid-dependent coagulation assays. LA are increasingly recognized as important predictors of thrombosis. However, the antigen specificity of LA is still poorly characterized. Growing evidence indicates that oxidized phospholipids are among the targets of anti-phospholipid antibodies. This prompted us to investigate the role of IgG directed against different oxidized phospholipids in 164 subjects without clotting factor defects that were tested for the presence of LA using a LA-sensitive activate partial thromboplastin time (aPTT-FSL) and a screening/confirmation assay based on diluted Russell's viper venom test (dRVVT-PL). The response to aPTT-FSL was significantly (P < 0.0005) associated with high titres of IgG against oxidized phosphatidylserine, phosphatidylethanolamine and phosphatidylinositol, whereas positivity to dRVVT-PL was associated with the elevation of IgG against oxidized phosphatidylserine, phosphatidylcholine, phosphatidylethanolamine (P < 0.0005) and phosphatidylinositol (P < 0.01). No difference in reactivity against oxidized cardiolipin was evident between the different groups. Positivity to the dRVVT-PL test was also associated significantly (P < 0.005) with the elevation of anti-cardiolipin and anti-beta(2)-glycoprotein-1 IgG. However, stepwise logistic regression demonstrated that IgG recognizing oxidized phosphatidylethanolamine and oxidized phosphatidylcholine were the only independent predictors of the response to dRVVT-PL assay, while IgG recognizing oxidized phosphatidylethanolamine and oxidized phosphatidylinositol were independent predictors of the response to aPTT-FSL test. In conclusion, autoantibodies against defined oxidized phospholipids are independent predictors of LA detection by aPTT-FSL or dRVVT-PL assays and might contribute to the variability often observed in the responses to the functional tests detecting LA.

Multicenter evaluation of five assays for myoglobin determination.

BACKGROUND: Lacking assay standardization, different myoglobin methods may produce results that differ significantly. METHODS: A multicenter study was carried out to compare the analytical performance of five commercially available assays for myoglobin measurement. Linearity, imprecision, interferences, and method comparison were studied according to NCCLS guidelines, whereas reference values were determined following IFCC recommendations. RESULTS: The BNA and Opus showed relatively high imprecision (all but one total CV >7.4%). Other assays showed lower CVs, but they varied among laboratories, particularly at a normal myoglobin concentration (Access, 6.0-11%; Hitachi, 3.8-5.8%; Stratus, 3.4-6.5%). Results were lower in anticoagulated samples on the Access, in heparin and citrate samples on the Stratus, and in citrate samples on the BNA and Opus, and increased in heparin and EDTA samples on the Hitachi. Use of separator gel produced results significantly lower (P <0.001) on the Hitachi and higher (P = 0.016) on the Opus. Bilirubin, turbidity, and hemoglobin had no effect on evaluated methods, but rheumatoid factor affected the Access. In method comparisons, high correlation coefficients (>/=0.98) were obtained. The Stratus gave higher results; however, the Access and BNA gave the lowest. The following upper reference limits (microgram/L) for men and women, respectively, were obtained: Access, 70 and 52; BNA, 51 and 49; Hitachi, 67 and 58; Opus, 80 and 50; and Stratus, 86 and 63. CONCLUSION: The possibility of high imprecision and marked disagreement among commercial myoglobin assays should be carefully considered in clinical practice.