ABSTRACT Objective: Low platelet reactivity levels are associated with higher risk of bleeding in patients receiving dual antiplatelet therapy relative to patients with optimal platelet blockade. This study set out to evaluate the prevalence of low platelet reactivity in patients with acute myocardial infarction treated with ticagrelor and aspirin. Methods: Patients admitted with acute myocardial infarction who were already undergoing dual antiplatelet therapy with aspirin and ticagrelor were enrolled. Blood samples were collected 1 hour before and 2 hours after the maintenance dose of ticagrelor to investigate trough and the peak effects of the drug respectively. Platelet reactivity was measured by three methods: Multiplate®, PFA-100® with Innovance® PFA-P2Y cartridge and PFA-100® with Collagen/ADP cartridge. Platelet reactivity was assessed in the presence of peak levels of ticagrelor and defined according to previously validated cut-offs for each method (<19 AUC, >299 seconds and >116 seconds respectively). The level of significance was set at p<0.05. Results: Fifty patients were enrolled (44% with ST-elevation). Median duration of DAPT was 3 days (interquartile range, 2-5 days). On average, peak and trough platelet reactivity were markedly low and did not differ between different methods. Low platelet reactivity was common, but varied according to analytic method (PFA-100®/Innovance®PFA-P2Y: 86%; Multiplate®: 74%; PFA-100®/Collagen/ADP: 48%; p<0.001). Conclusion: Low platelet reactivity was very common in patients with acute myocardial infarction submitted to dual antiplatelet therapy with ticagrelor and aspirin. Findings of this study justify the investigation of less intensive platelet inhibition strategies aimed at reducing the risk of bleeding in this population, such as lower dose regimens or monotherapy with P2Y12 inhibitors.

A água é um reagente utilizado na maioria dos testes laboratoriais e por isso deve seguir um padrão de controle de qualidade rigoroso. O fornecimento urbano de água apresenta moléculas orgânicas, íons inorgânicos, partículas, coloides, gases, bactérias e seus produtos, que podem alterar os resultados dos exames laboratoriais e causar eventuais erros e falhas mecânicas em equipamentos analíticos. Para remover essas impurezas, é necessário recorrer a uma combinação de tecnologias de purificação. Há várias organizações que especificam normas sobre a água reagente, a fim de minimizar sua interferência nos ensaios laboratoriais. A maioria dos laboratórios utiliza as normas estabelecidas pelo Clinical and Laboratory Standards Institute (CLSI) que classifica a água em: clinical laboratory reagent water (CLRW), special reagent water (SRW) e instrumental feed water (IFW). O monitoramento da qualidade é realizado pela determinação de resistividade, condutividade, carbono orgânico total (TOC), controle microbiológico e endotoxinas. Os parâmetros são avaliados de acordo com a periodicidade estabelecida pela norma utilizada. Neste artigo, discutem-se a importância da água utilizada nos procedimentos laboratoriais, o controle da qualidade e as interferências nos ensaios laboratoriais.

Water is a reagent used in most laboratory tests and, therefore, must follow stringent quality control standards. The urban water supply has organic molecules, inorganic ions, particles, colloids, gases, bacteria and their products, which may alter laboratory test results and cause occasional errors and mechanical failures in diagnostic equipment. To remove these impurities, it is necessary to use a combination of purification technologies. There are several organizations that specify reagent water standards to minimize its interference in laboratory assays. Most laboratories set standards established by the Clinical and Laboratory Standards Institute (CLSI), which classifies the type of water as follows: clinical laboratory reagent water (CLRW), special reagent water (SRW) and instrumental feed water (IFW). The quality monitoring is performed by means of assessing the resistivity, conductivity, total organic carbon (TOC), microbial control and endotoxins. The parameters are evaluated in accordance with the frequency determined by the standard used. In this article we discuss the importance of water employed in laboratory procedures, its quality control and its interference in laboratory assays.