Determinants of the interindividual variability in response to antiplatelet drugs

The aim of this review article is to discuss the main determinants of the interindividual variability in response to antiplatelet agents. The main sources of pharmacokinetic and pharmacodynamic variability are reviewed, with particular emphasis on aspirin and clopidogrel. The term 'resistance' is uninformative of the mechanism(s) underlying interindividual variability in response to these antiplatelet agents, and is potentially misleading. Increased awareness of the distinct factors potentially interfering with the desired antiplatelet effects of aspirin or clopidogrel, particularly avoidable drug interactions, may ultimately result in better patient management than requesting unnecessary costly tests of platelet function. Similarly, new studies addressing the interindividual variability in response to these antiplatelet agents should rely upon mechanism-based biochemical end-points rather than platelet aggregation measurements. As with any drug used to prevent atherothrombosis, treatment 'failure' can occur with aspirin or clopidogrel perhaps not surprisingly, given the multifactorial nature of atherothrombosis. There is no scientific basis for changing antiplatelet therapy in the face of a treatment 'failure', as we cannot be sure whether a second vascular event occurring in the same patient will reflect the same pathophysiological event that led to the first. Moreover, we have no controlled evidence that changing therapy is a more effective strategy than maintaining an evidence-based therapy.     

Frequency and specificity of the Trima Accel "verify WBCs" advisory: considerations for product management

BACKGROUND: The Trima Accel displays a “verify WBCs” message if the plateletpheresis product (PLT) may not be leukoreduced (LR). Most blood banks require sensitive white blood cell (WBC) testing of these PLTs by flow or Nageotte. We evaluated how often these PLTs were non‐LR by European or US Food and Drug Administration (FDA) criteria and whether sensitive WBC testing is necessary. STUDY DESIGN AND METHODS: Phase 1 reviewed the frequency of this message with various procedure types and the flow WBC results for PLTs with or without the message. Phase 2 assessed how many FDA LR failures were detectable by a hematology analyzer. In Phase 3, PLTs were managed by hematology analyzer results. RESULTS: In Phase 1, 3.8% of PLT‐only and 11.1% of PLT‐plasma collections had the “verify WBCs” message. Only 1% of “verify” PLTs contained more than 1 × 10⁶ WBCs and only 0.5% were FDA LR failures. In Phase 2, 10 of 670 “verify” PLTs and one nonflagged PLT were FDA LR failures. Six of 11 LR failures had hematology analyzer WBC concentrations of 0.4 × 10⁹/L or higher. In Phase 3, “verify” PLTs were allowed in inventory if hematology analyzer WBC concentration was below 0.4 × 10⁹/L; inventory quality control showed no FDA LR failures by flow. Trima Version 6.0 software lowered the “verify” message frequency in PLT‐plasma procedures but not in PLT‐only procedures. CONCLUSION: Four percent of Trima PLT collections have the “verify WBCs” message but almost all of these are LR by European and FDA criteria. Fifty percent of FDA LR failures were detectable by a hematology analyzer. Sensitive WBC testing of all “verify WBCs” PLTs may not be necessary to satisfy LR quality assurance requirements.     

Do EMS Providers Accurately Ascertain Anticoagulant and Antiplatelet Use in Older Adults with Head Trauma?

Objective: Prehospital provider assessment of the use of anticoagulant or antiplatelet medications in older adults with head trauma is important. These patients are at increased risk for traumatic intracranial hemorrhage and therefore field triage guidelines recommend transporting these patients to centers capable of rapid evaluation and treatment. Our objective was to evaluate EMS ascertainment of anticoagulant and antiplatelet medication use in older adults with head trauma. Methods: A retrospective study of older adults with head trauma was conducted throughout Sacramento County. All 5 transporting EMS agencies and all 11 hospitals in the county were included in the study, which ran from January 2012 to December 2012. Patients ≥55 years who were transported to a hospital by EMS after head trauma were included. We excluded patients transferred between two facilities, patients with penetrating head trauma, prisoners, and patients with unmatched hospital data. Anticoagulant and antiplatelet use were categorized as: warfarin, direct oral anticoagulants (DOAC; dabigatran, rivaroxaban, and apixaban), aspirin, and other antiplatelet agents (e.g., clopidogrel and ticagrelor). We calculated the percent agreement and kappa statistic for binary variables between EMS and emergency department (ED)/hospital providers. A kappa statistic ≥0.60 was considered acceptable agreement. Results: After excluding 174 (7.6%) patients, 2,110 patients were included for analysis; median age was 73 years (interquartile range 62–85 years) and 1,259 (60%) were male. Per ED/hospital providers, the use of any anticoagulant or antiplatelet agent was identified in 595 (28.2%) patients. Kappa statistics between EMS and ED/hospital providers for the specific agents were: 0.76 (95% CI 0.71–0.82) for warfarin, 0.45 (95% CI 0.19–0.71) for DOAC agents, 0.33 (95% CI 0.28–0.39) for aspirin, and 0.51 (95% CI 0.42–0.60) for other antiplatelet agents. Conclusions: The use of antiplatelet or anticoagulant medications in older adults who are transported by EMS for head trauma is common. EMS and ED/hospital providers have acceptable agreement with preinjury warfarin use but not with DOAC, aspirin, and other antiplatelet use.     

Novice nurses’ experiences from teamwork in the emergency department: A qualitative content analysis

Background and aimTeamwork is assumed crucial in nursing. Nevertheless, nursing shortages in medical centers have thus far compelled nurse managers to use novice nurses. The present study aimd to explaining the challenges and experiences of novice nurses regarding teamwork in emergency departments.Materials and methodsUsing qualitative content analysis, 11 novice nurses working at emergency department, participated in this study. Data were collected with semi structured interview and analyzed by Graneheim and Lundman.ResultsThe data analysis led to the emergence of four themes of “essential teamwork skills development”, “contradictory relationships between team members”, “unpleasant feelings and experiences”, and, “personal growth and maturation during teamwork”.ConclusionFostering different personal aspects as prerequisites for teamwork, novice nurses will be able to deal with unpleasant feelings and experiences as well as contradictory relationships between team members in an effective manner. This challenging experience will thus give rise to personal growth and maturation during teamwork among them in emergency department.     

Mechanism of action and clinical development of platelet thrombin receptor antagonists

Atherothrombotic disease is the leading cause of death worldwide. Currently, dual antiplatelet therapy with aspirin and ADP receptor antagonists has shown improved short- and long-term clinical outcomes but is associated with increased bleeding risk, and the rates of recurrent ischemic events still remain high. Selective inhibition of the principal protease-activated receptor (PAR)-1 for thrombin, the most potent platelet activator, represents a promising novel strategy to reduce ischemic events without increasing the risk of bleeding. Two PAR-1 antagonists are currently being tested in clinical trials: SCH 530348 and E5555. Both have demonstrated an antiplatelet effect without increasing bleeding time in preclinical trials. Results of Phase II trials showed that SCH 530348, in addition to standard antiplatelet therapy, was well tolerated and not associated with increased bleeding risk. The safety and tolerability of E5555 is being evaluated in patients with coronary artery disease and non-ST-segment elevation acute coronary syndrome in four Phase II clinical trials. Two large-scale Phase III trials assessing the efficacy of SCH 530348 in addition to the standard of care are currently ongoing. This article provides an overview of the current status of knowledge on platelet thrombin receptor antagonists, focusing on pharmacologic properties and clinical development.     

Update on the clinical development of cangrelor

Antiplatelet drugs represent the cornerstone of treatment for cardiovascular atherothrombotic disease. Dual oral antiplatelet therapy with aspirin and oral ADP-receptor antagonists, such as clopidogrel, has been the standard choice for prevention of ischemic events in patients with acute coronary syndrome and in those undergoing percutaneous coronary intervention. However, due to the limitations of clopidogrel, such as interindividual-response variability, drug–drug interactions, slow onset of action and irreversible inhibitory effects, novel antiplatelet agents are under clinical development. Cangrelor is a reversible, potent, competitive inhibitor of the ADP P2Y₁₂ receptor that is administered intravenously and rapidly achieves near complete inhibition of ADP-induced platelet aggregation. These pharmacological properties make cangrelor a promising drug for clinical use. However, recent large-scale Phase III clinical investigations failed to show significant clinical benefit on the primary end point with cangrelor. This article provides an overview of the current status of knowledge on cangrelor, focusing on its pharmacologic properties and clinical development.     

Effect of Aspirin and Antiplatelet Drugs on the Outcome of the Fecal Immunochemical Test

ObjectiveTo evaluate the effect of aspirin and nonaspirin antiplatelet agents (NAAAs) on the performance of the fecal immunochemical test (FIT).Participants and MethodsWe performed a post hoc analysis of results from a clinical trial that involved 28,696 asymptomatic average-risk men and women aged 50 to 69 years invited to participate in a colorectal cancer screening program with FIT between November 1, 2008, and June 31, 2011.ResultsThe test was returned by 6390 individuals (22.3%), of whom 5821 (91.1%) reported not using antiplatelet drugs (nonusers group) and 569 (8.9%) reported using these drugs at the time of testing (users group). The FIT result was positive in 48 of 569 users (8.4%) and 365 of 5821 nonusers (6.3%) (P=.05). A positive FIT result was found in 7.3% (28/384) of aspirin users, 7.1% (10/140) of NAAA users, and 22.2% (10/45) of those undergoing dual antiplatelet therapy (DAPT) (aspirin plus an NAAA). The DAPT subgroup had a significantly higher positive FIT rate than the nonuser group (odds ratio, 3.5; 95% CI, 1.7-7.3; P<.05). The positive predictive value (PPV) for advanced neoplasia (AN) in nonusers was 50.4% vs 50.0% in users (P = .40). The PPV for AN was 57.0% in aspirin users, 30.0% in NAAA users, and 50.0% in DAPT users, without statistically significant differences between the user and nonuser groups.ConclusionThe use of DAPT increased the rate of positive FIT results. Use of aspirin, NAAAs, or both did not modify the PPV for AN in this population-based colorectal screening program.Trial Registrationclinicaltrials.gov Identifier: NCT00906997     

Current controversies in the use of aspirin and ticagrelor for the treatment of thrombotic events

Introduction: A P2Y₁₂ inhibitor plus aspirin is the most widely used antiplatelet strategy to prevent adverse outcomes in the setting of atherothrombotic vascular disease.

Areas covered: A paucity of robust evidence for an optimal dose, gastrointestinal toxicity, ineffectiveness in high-risk patients and interactions with other antiplatelet agents, are major controversies associated with aspirin therapy. Ticagrelor is a reversibly binding oral P2Y₁₂ receptor blocker that mediates potent inhibition of adenosine diphosphate-induced platelet function. It is more effective than clopidogrel in preventing thrombotic events in acute coronary syndrome patients. The absence of a beneficial effect for ticagrelor versus clopidogrel in ACS observed in the North American subgroup of the PLATelet inhibition and patient Outcomes (PLATO) trial has been attributed to a higher concomitant aspirin dose.

Expert commentary: Ongoing studies are now investigating the plausibility of removing aspirin therapy in the setting of potent P2Y₁₂ receptor blockade via ticagrelor monotherapy or replacing aspirin with an oral anticoagulant.     

Living with chronic headache: a qualitative study exploring goal management in chronic headache

Abstract

Objectives: Effective goal management may potentially prevent or reduce disability in chronic pain. The aim of this study was to gain insight into the nature of goal management in the context of chronic headache (CH).

Methods: Interviews with 20 patients were conducted, coded, and analyzed using a combined data-driven and theory-driven approach. The dual process model (DPM) was used as a theoretical framework for this study.

Results: Participants used a combination of strategies to regain and maintain a balance between personal goals and resources available for goal pursuit. Furthermore, their retrospective reports indicated a development in strategy use of time. Three goal management phases were identified: (1) a “persistence phase,” characterized by the use of “resource-depleting” assimilative strategies to remain engaged in goals, (2) a “reorientation phase” in accommodative strategies were used to regain balance, and (3) a “balancing phase” in which a combination of “resource-depleting” and “resource-replenishing” assimilative strategies was used to maintain balance.

Conclusions: Goal management is a dynamic process that may contribute to the development of, and recovery from, headache-related disability. Rehabilitation services offered to individuals with CH should target this process to promote optimal functioning.

• Implications for Rehabilitation

• Individuals with chronic headache use assimilative and accommodative goal management strategies to be able to pursue personal goals despite the limitations of chronic headache.

• Before accommodating goals to the limitations of chronic headache, many patients go through a phase of persistence, characterized by the use of resource-depleting assimilative strategies.

• A reorientation phase, characterized by accommodation of goals to the limitations of chronic headache, allows patients to adopt a more balanced way of pursuing personal goals.

     

A review on adherence management in patients on oral cancer therapies

PurposeThere is currently an ongoing paradigm shift in cancer treatment from intravenous (IV) chemotherapeutics to oral therapies. Additionally, the increased use of long-term maintenance therapy with oral targeted agents or chemotherapy is contributing to a shift toward a chronic-disease model. This shift is creating challenges and responsibilities for health care professionals in patient adherence management. This article will inform health care professionals of current trends and describe ways that they can overcome common barriers to adherence. A comprehensive review of recommendations and evidence derived from oncological studies describing adherence to oral targeted therapies and maintenance chemotherapy will provide guidance for the use of emerging oral maintenance therapies.MethodsArticles in the scientific literature were reviewed if published between January 1985 and November 2010. Searches were conducted using the PubMed database—search terms included “oral therapy,” “chemotherapy,” “cancer,” and “adherence” or “compliance.”ResultsThe change from IV therapy administered and monitored in hospitals or clinics to self-administered outpatient oral treatments decreases the likelihood of adherence. Methods, such as patient education and monitoring and involvement of family or caretakers, can improve adherence in patients undergoing treatment.ConclusionsAt treatment onset, oncology nurses can engage patients directly in a collaborative dialogue, and when issues affecting adherence arise, oncology nurses may limit nonadherence by providing individually tailored educational material. A practical approach to patient education, along with building strong health care provider–patient relationships, can help patients overcome nonadherence to new oral anticancer therapies and treatment paradigms.     

Aspirin, 110 years later

Summary.  Although conceived at the end of the 19th century as a synthetic analgesic agent with improved gastric tolerability vs. naturally occurring salicylates, acetylsalicylic acid (marketed as aspirin in 1899) turned out to be an ideal antiplatelet agent about 90 years later, following the understanding of its mechanism of action, the development of a mechanism-based biomarker for dose-finding studies, and the initiation of a series of appropriately sized, randomized clinical trials to test its efficacy and safety at low doses given once daily. At the turn of its 110th anniversary, aspirin continues to attract heated debates on a number of issues including (i) the optimal dose to maximize efficacy and minimize toxicity; (ii) the possibility that some patients may be 'resistant' to its antiplatelet effects; and (iii) the balance of benefits and risks in primary vs. secondary prevention.     

Utilization of antithrombotic therapy for stroke prevention in atrial fibrillation: a cross‐sectional baseline analysis in general practice

What is known and objective: Antithrombotics for stroke prevention in atrial fibrillation (AF) are reportedly underutilised. Since the burden of care lies within general practice, attention must be paid to identifying and addressing practice gaps in this setting. The objective of this study was to determine the contemporary utilisation of antithrombotic therapy for stroke prevention in AF within Australian general practice (GP). Methods: Data pertaining to AF patients’ (aged ≥65 years) were collected from GP surgeries in New South Wales, Australia, using purpose‐designed data collection forms; extracted data comprised patients’ medical histories, current pharmacotherapy, and relevant characteristics. Results and Discussion: Data pertaining to 393 patients (mean age 78·0 ± 7·0 years) were reviewed. Overall, most (98·5%) patients received antithrombotic therapy. Among the 387 patients using antithrombotics, most (94·1%) received mono‐therapy. “Warfarin ± antiplatelet” was most frequently used (81·7%); 77·5% used “warfarin” as a monotherapy, followed by “dabigatran ± clopidogrel” (11·6%), “aspirin” (5·9%) and “clopidogrel” alone (0·8%). High stroke risk and low bleeding risk were associated with increased use of “warfarin ± antiplatelet” therapy. Older patients (≥80 years) were more likely to receive ‘nil therapy’ (P = 0·04), and less likely to receive dual and triple antithrombotic therapy. Conclusion: We found an encouraging improvement compared to previous studies in the utilisation of antithrombotic therapy for stroke prevention in AF within general practice. Warfarin is now utilised as the mainstay therapy, followed by aspirin, although the novel oral anticoagulants are entering the spectrum of therapies used. Consideration needs to be given to the potential impact of the newer agents and their scope of use.     

Convection-enhanced delivery of 131I-chTNT-1/B mAB for treatment of high-grade adult gliomas

Introduction: Despite treatment advances for malignant gliomas in adults, prognosis remains poor, largely due to the infiltrative and heterogeneous biology of these tumors. Response to adjuvant therapy is not always uniform and the blood–brain barrier prevents the majority of chemotherapeutics from adequately reaching primary tumor sites. These obstacles necessitate development of novel delivery methods and agents.

Areas covered: ¹³¹I-chTNT-1/B mAB (Cotara) is a genetically engineered chimeric monoclonal antibody that binds to the DNA–histone H1 complex. It carries ¹³¹I, which delivers sufficient energy to kill adjacent tumor cells. Through convection-enhanced delivery (CED) it provides radioimmunotherapy directly to the resection cavity. We review the pharmacology and clinical experience with ¹³¹I-chTNT-1/B mAB, detailing results of completed Phase I and II trials.

Expert opinion: Novel agents and therapeutic modalities, such as ¹³¹I-chTNT-1/B mAB, are of interest for treatment of malignant glioma, for which the prognosis continues to be dismal. ¹³¹I-chTNT-1/B mAB targets tumor cells and radioisotope labeling allows radiation delivery to the tumor with sharp fall-off. Data from Phase I and II trials of CED delivery of ¹³¹I-chTNT-1/B mAB shows it is well tolerated. Phase II trial data suggests it could be promising therapeutically, though conclusions about efficacy require further trials and clinical experience. The compound is currently in a Phase II trial for dose confirmation in patients with malignant gliomas.     

Interleukin-21: updated review of Phase I and II clinical trials in metastatic renal cell carcinoma,metastatic melanoma and relapsed/refractory indolent non-Hodgkin's lymphoma

Importance to the field: In advanced renal cell cancer and malignant melanoma, the current FDA approved immune modulators, such as IL-2, are the only agents which provide a durable complete remission. These responses, however, occur in < 10% of treated patients and their applicability is limited to selected patients because of their toxicity. The identification of new immunotherapeutic agents with an improved response rate and toxicity profile would represent a significant advancement in the treatment of these malignancies.

Areas covered in this review: This is a comprehensive review of IL-21 including its pharmacology and current developmental status. A literature review was performed using all PubMed listed publications involving IL-21, including original research articles, reviews and abstracts. It also includes a review of current ongoing trials and information from the official product website.

What the reader will gain: Recombinant IL-21 (rIL-21) is a new immune modulator currently undergoing Phase I and II testing. It is a cytokine with a four helix structure that has structural and sequence homology to IL-2 and -15, but also possesses many unique biological properties. In this review, we evaluate the development, pharmacologic properties, safety profile and current clinical efficacy of rIL-21.

Take home message: rIL-21 has an acceptable safety profile and encouraging single agent activity in early phase renal cell carcinoma and melanoma clinical trials.     

Modification and Initial Psychometric Evaluation of the Physical Health Attitude Scale for Use in the Canadian Mental Health and Addictions Context

Introduction: The Physical Health Attitude Scale (PHASe) tool was developed to better understand mental health nurses’ attitudes towards their involvement and confidence in physical health care. This tool has been used in the United Kingdom and Australia; however, it has not been used in Canada.

Aim: This study aims to modify and provide an initial psychometric evaluation of the PHASe tool for use in a Canadian mental health and addictions context.

Methods: In Phase 1, clinical experts (n?=?8) were consulted to provide feedback on the content and face validity of the PHASe tool. In Phase 2, the PHASe tool was piloted with nurses at a large urban mental health and addiction organization in Ontario, Canada (n?=?77).

Results: In Phase 1, 4 items were added and 5 items were removed from the tool based on feedback provided by experts. In Phase 2, 12 poorly correlated items were removed. A two-factor solution was identified, with subscales “confidence” and “barriers and attitudes”.

Discussion: Initial psychometric evaluation suggests that a revised 15-item version of the PHASe tool is valid and reliable in a Canadian mental health and addictions context; however, more testing is recommended in larger, more diverse samples.     

Pharmacogenomics in cardiovascular disease: focus on aspirin and ADP receptor antagonists

Antiplatelet agents like aspirin and adenosine diphosphate receptor antagonists are effective in reducing recurrent ischemic events. Considerable inter‐individual variability in the platelet inhibition obtained with these drugs has initiated a search for explanatory mechanisms and ways to improve treatment. In recent years, numerous genetic polymorphisms have been linked with reduced platelet inhibition and lack of clinical efficacy of antiplatelet drugs, particularly clopidogrel and aspirin. Consequently, attempts to adjust antiplatelet treatment according to genotype have been made, but the clinical benefit has been modest in studies performed so far. The progress in genome science over the last decade and the declining cost of sequencing technologies hold the promise of enabling genetically tailored antiplatelet therapy. However, more evidence is needed to clarify which polymorphisms may serve as targets to improve treatment. The present review outlines the panel of polymorphisms affecting the benefit of aspirin and adenosine diphosphate receptor antagonists, including novel and ongoing studies evaluating whether genotyping may be beneficial in tailoring antiplatelet therapy.     

Aspirin for the primary prevention of cardiovascular disease: latest evidence

ABSTRACT

Introduction: While the clinical merits of aspirin in secondary cardiovascular disease (CVD) prevention remain undisputed, its role in primary prevention is controversial. Recently, three trials of primary prevention reported neutral net benefit results or evidence of harm for aspirin in patients with no overt CVD.

Areas covered: This article aims to inform clinical practitioners by appraising the current body of evidence on the use of aspirin for primary CVD prevention, ranging from general pharmacology to clinical outcomes and future directions.

Expert opinion: Based on meta-analyses incorporating latest trials in the field of primary prevention, the modest reduction in ischemic events with aspirin, if any, is offset by a modest increase in nonfatal bleeding. Improved control of CVD risk factors and broader use of statins may have reduced the thrombotic complications of atherosclerosis, thus limiting the opportunity for aspirin to prevent clinical CVD events in the contemporary era. As such, decision-making about aspirin for primary prevention is challenging even when selected patients are considered and involves careful weighing of risks and benefits. Ongoing investigations conducted in patients with cancer could rapidly modify the current perception of the unfavorable benefit-risk ratio of aspirin in patients with no overt CVD.     

Taking back a little of what you have lost: the meaning of using an Environmental Control System (ECS) for people with high cervical spinal cord injury

Abstract

Purpose: Assistive technologies have deep and personal meanings for people with disabilities. This study sought to provide an in-depth exploration of the subjective meaning of Environmental Control System (ECS) use for people with high cervical spinal cord injury.

Materials and method: Interpretative Phenomenological Analysis (IPA) was used to explore the personal meaning of ECS. In-depth interviews with five participants were analyzed according to recommended IPA guidelines to produce a rich phenomenological account of lived experience.

Results: This study identified two overarching themes, one of which was the subject of an earlier publication. This paper focuses on the second theme “taking back a little of what you have lost” and its two main components “reclaiming a little doing” and “feeling enabled”. Doing everyday things, being less dependent on others and feeling safer and less needy all contributed to participants experience of regaining something important of what had been lost.

Conclusions: A nuanced range of meanings, demonstrating how “a little can mean a lot” emerged from this study. For those with high cervical spinal cord injury, “reclaiming a little doing” resulted in subtle, but subjectively significant, improvements in identity, relationships and well-being, while “feeling enabled” was both enjoyable and empowering and led to an increased sense of safety and reduced neediness. The potentially powerful impact on individuals with life-altering injuries of reclaiming a little of what they had lost, supports the value of more widespread access to and provision of ECS.

• Implications for rehabilitation

• While ECS use produces only a “little” objective change in activity levels, it subjectively means “a lot” to people with high level injuries.

• ECS enable people to “do” everyday things as well help in supporting them to “feel” less dependent and needy.

• Using ECS facilitates much more than functional tasks and a sense of security. It helps promote positive self-perception and continuity of being.

• It is important for those with high cervical spinal cord injuries to have access to ECS to ensure they can enjoy both psychological and physical benefits.

     

Laboratory signs of aspirin response in haemodialysis patients

Abstract

Introduction. Aspirin is effective in the secondary prevention and high-risk primary prevention of cardiovascular events. However, clinical and laboratory evidence demonstrates diminished or no response to aspirin in some patients. This study was designed to assess aspirin response in haemodialysis patients. Methods. We prospectively enrolled 78 haemodialysis patients (28 female; 58.4 ± 12.6 years old) and 79 patients (29 female; 58.4 ± 10.6 years old) with normal renal function (glomerular filtration rate (GFR) >60 mL/min/1.73 m²). All subjects in both the haemodialysis patient group and the control group were taking aspirin (80–300 mg) for at least 30 days and were not taking other antiplatelet agents. Platelet function was assessed by arachidonic acid-induced aggregometry with a Multiplate analyser (Dynabyte Medical, Munich, Germany). Multiplate electrode aggregometry values below 300 AU were applied as a cut-off for response to aspirin. Results. Aspirin non-response was two-fold more prevalent in haemodialysis patients (42.3%) than in patients with normal renal function (21.5%), and this difference was statistically significant (p = 0.005). The two groups were similar in terms of sex, age, tobacco use, the presence of diabetes mellitus, and platelet count. Conclusions. The frequency of aspirin non-response as defined in this study was higher in haemodialysis patients than in patients with normal renal function. However, larger subsets of patients are needed to confirm the present study.