Platelet function assays for the diagnosis of aspirin resistance

Prevalence of risk factors for venous thromboembolism and aspirin resistance in Australian patients undergoing total hip and knee arthroplasty

INTRODUCTION

Aspirin is used for venous thromboembolism (VTE) prophylaxis after total hip and knee arthroplasty (THA/TKA). However, its efficacy is unclear in patients with multiple VTE risk factors and at risk of aspirin resistance (AR).

BACKGROUND AND AIMS

To determine the prevalence of risk factors for VTE and AR in patients after THA/TKA and to determine the relationship between risk factors and drugs prescribed for thromboprophylaxis.

METHODS

A retrospective cohort study of elective-THA/TKA in six Australian hospitals over a 1-year period. Medical records were manually reviewed to determine demographics, thromboprophylaxis regimen and presence of risk factors. The relationship between individual and cumulative risk factors with the thromboprophylaxis regimen was determined.

RESULTS

In total, 1011 patients were included with a mean (SD) age of 65.9 (±11.0) years, and 56.4% were female. The five most prevalent risk factors were obesity (59.1%), age ≥65 years (58.2%), hypertension (45.3%), dyslipidaemia (35.9%) and diabetes (19.7%). Most patients had ≥1 risk factor for VTE (93.6%) and AR (93.6%), with 49.0% and 35.0% having ≥3 concurrent VTE and AR risk factors, respectively. The only significant relationship between risk factors and drugs was diabetes (P < 0.01). Rivaroxaban was more commonly used as the number of concurrent VTE risk factors increased (P < 0.05).

CONCLUSION

Patients had a high prevalence of VTE and AR risk factors, suggesting aspirin may not be beneficial in many patients. Only diabetes was linked to the selection of thromboprophylaxis. Patients who received rivaroxaban had a greater average number of VTE risk factors. Guidelines should promote individualised prescribing in higher-risk patients.

Genetic factors related to aspirin resistance using the Multiplate® device in Hong Kong Chinese patients with stable coronary heart disease

Objective

Associations between single nucleotide polymorphisms (SNPs) and aspirin resistance (AR) have been studied with variable results. The associations of genetic variants with AR may be helpful to explain why some individuals demonstrate aspirin insensitivity with this anti-platelet therapy. The purpose of this research was to investigate the effect of different genotypes in candidate genes on aspirin response in patients taking long-term aspirin therapy by measuring the serum thromboxane B2 (TXB2) and platelet function using the Multiplate® analyser.

Methods

A total of 266 patients with stable coronary heart disease (CHD) taking low-dose aspirin for long periods of time and without any other anti-platelet drugs medications were enrolled into the study. They were required to take 80 mg of aspirin every morning for a week including the day before blood tests. Blood samples were collected 24 h after the last dose. The 80 mg dose of aspirin was taken orally and blood samples were collected again 1 h later. The serum TXB2 levels were measured in samples at 24 h post-dose and 1 h post-dose using the EIA kit and platelet activity was determined using the Multiplate® Impedance Platelet Aggregometry (ASPI) assay. Genotyping assays were performed by the TaqMan SNP genotyping technique.

Results

Of the 266 patients, only 251 patients were enrolled in the present study. The PTGS1/COX1-1676 A > G (rs1330344) and the PTGS2/COX2-765 G > C (rs20417) SNPs showed significant associations with the ASPI measurements in samples taken at 24 h post-dose, but not with the values at 1 h post-dose or with the TXB2 levels (P < 0.05).

Conclusions

Our results suggest that polymorphisms in the PTGS1/COX1 and the PTGS2/COX2 genes may be associated with reduced anti-aggregatory effects and increased the risk of AR, but future larger-scale cohort studies are necessary for further validation.

Advances in Platelet-Dysfunction Diagnostic Technologies

The crucial role of platelets in hemostasis and their broad implications under various physiological conditions underscore the importance of accurate platelet-function testing. Platelets are key to clotting blood and healing wounds. Therefore, accurate diagnosis and management of platelet disorders are vital for patient care. This review outlines the significant advancements in platelet-function testing technologies, focusing on their working principles and the shift from traditional diagnostic methods to more innovative approaches. These improvements have deepened our understanding of platelet-related disorders and ushered in personalized treatment options. Despite challenges such as interpretation of complex data and the costs of new technologies, the potential for artificial-intelligence integration and the creation of wearable monitoring devices offers exciting future possibilities. This review underscores how these technological advances have enhanced the landscape of precision medicine and provided better diagnostic and treatment options for platelet-function disorders.

Monitoring of Antiplatelet Therapy

In the late 1990s, the antithrombotic antiplatelet agent, clopidogrel, a P2Y12 inhibitor, was introduced. Around the same time, there was an increase in a number of new methods to measure platelet function (e.g., PFA-100 in 1995), and this has continued. It became evident that not all patients responded to clopidogrel in the same way and that some patients had a relative "resistance" to therapy, termed "high on-treatment platelet reactivity." This then led to some publications to advocate platelet function testing being used for patients on antiplatelet therapy. Platelet function testing was also suggested for use in patients awaiting cardiac surgery after stopping their antiplatelet therapy as a way of balancing thrombotic risk pre-surgery and bleeding risk perioperatively. This chapter will discuss some of the commonly used platelet function tests used in these settings, particularly those that are sometimes referred to as point-of-care tests or that require minimal laboratory sample manipulation. The latest guidance and recommendations for platelet function testing will be discussed following several clinical trials looking at the usefulness of platelet function testing in these clinical settings.

Genetic Association Study and Machine Learning to Investigate Differences in Platelet Reactivity in Patients with Acute Ischemic Stroke Treated with Aspirin

Aspirin resistance (AR) is a pressing problem in current ischemic stroke care. Although the role of genetic variations is widely considered, the data still remain controversial. Our aim was to investigate the contribution of genetic features to laboratory AR measured through platelet aggregation with arachidonic acid (AA) and adenosine diphosphate (ADP) in ischemic stroke patients. A total of 461 patients were enrolled. Platelet aggregation was measured via light transmission aggregometry. Eighteen single-nucleotide polymorphisms (SNPs) in ITGB3, GPIBA, TBXA2R, ITGA2, PLA2G7, HMOX1, PTGS1, PTGS2, ADRA2A, ABCB1 and PEAR1 genes and the intergenic 9p21.3 region were determined using low-density biochips. We found an association of rs1330344 in the PTGS1 gene with AR and AA-induced platelet aggregation. Rs4311994 in ADRA2A gene also affected AA-induced aggregation, and rs4523 in the TBXA2R gene and rs12041331 in the PEAR1 gene influenced ADP-induced aggregation. Furthermore, the effect of rs1062535 in the ITGA2 gene on NIHSS dynamics during 10 days of treatment was found. The best machine learning (ML) model for AR based on clinical and genetic factors was characterized by AUC = 0.665 and F1-score = 0.628. In conclusion, the association study showed that PTGS1, ADRA2A, TBXA2R and PEAR1 polymorphisms may affect laboratory AR. However, the ML model demonstrated the predominant influence of clinical features.

The Translation and Commercialisation of Biomarkers for Cardiovascular Disease—A Review

As a leading cause of mortality and morbidity worldwide, cardiovascular disease and its diagnosis, quantification, and stratification remain significant health issues. Increasingly, patients present with cardiovascular disease in the absence of known risk factors, suggesting the presence of yet unrecognized pathological processes and disease predispositions. Fortunately, a host of emerging cardiovascular biomarkers characterizing and quantifying ischaemic heart disease have shown great promise in both laboratory settings and clinical trials. These have demonstrated improved predictive value additional to widely accepted biomarkers as well as providing insight into molecular phenotypes beneath the broad umbrella of cardiovascular disease that may allow for further personalized treatment regimens. However, the process of translation into clinical practice – particularly navigating the legal and commercial landscape – poses a number of challenges. Practical and legal barriers to the biomarker translational pipeline must be further considered to develop strategies to bring novel biomarkers into the clinical sphere and apply these advances at the patient bedside. Here we review the progress of emerging biomarkers in the cardiovascular space, with particular focus on those relevant to the unmet needs in ischaemic heart disease.

Comparative Study of Ex Vivo Antiplatelet Activity of Aspirin and Cilostazol in Patients with Diabetes and High Risk of Cardiovascular Disease

BACKGROUND

The role of aspirin in primary cardiovascular disease prevention in patients with diabetes remains controversial. However, some studies have suggested beneficial effects of cilostazol on cardiovascular disease in patients with diabetes. We prospectively investigated the antiplatelet effects of cilostazol compared with aspirin in patients with diabetes and cardiovascular risk factors.

METHODS

We randomly assigned 116 patients with type 2 diabetes and cardiovascular risk factors but no evident cardiovascular disease to receive aspirin at a dose of 100 mg or cilostazol at a dose of 200 mg daily for 14 days. The primary efficacy outcome was antiplatelet effects of aspirin and cilostazol assessed with the VerifyNow system (aspirin response units [ARU]) and PFA-100 (closure time [CT]). Secondary outcomes were changes of clinical laboratory data (ClinicalTrials.gov Identifier: NCT02933788).

RESULTS

After 14 days, there was greater decrease in ARU in aspirin (-28.9%±9.9%) compared cilostazol (-0.4%±7.1%, P<0.001) and was greater increase in CT in aspirin (99.6%±63.5%) compared cilostazol (25.7%±54.1%, P<0.001). The prevalence of aspirin resistance was 7.5% according to VerifyNow (defined by ARU ≥550) and 18.9% according to PFA-100 (CT <192 seconds). Compared with aspirin, cilostazol treatment was associated with increased high density lipoprotein cholesterol (7.1%±12.7% vs. 4.2%±18.0%, P=0.006) and decreased triglycerides (-9.4%±33.7% vs. 4.4%±17.57%, P=0.016). However, there were no significant changes in total and low density lipoprotein cholesterol, C-reactive protein level, and cluster of differentiation 40 ligand between cilostazol and aspirin groups.

CONCLUSION

Aspirin showed better antiplatelet effects assessed with VerifyNow and PFA-100 compared with cilostazol. However, there were favorable changes in atherogenic dyslipidemia only in the cilostazol.