Utility of in vitro closure time test for evaluating platelet-related primary hemostasis in dialysis patients

Clinical Impact of the Use of Warfarin in Patients with Atrial Fibrillation Undergoing Maintenance Hemodialysis

Background: We evaluated the impact of warfarin use on the clinical outcomes of patients with atrial fibrillation who were undergoing hemodialysis (HD). Methods: A retrospective analysis was conducted utilizing data from patients undergoing maintenance HD who participated in HD quality assessment programs. Patients who were assigned the diagnostic code for atrial fibrillation (n = 4829) were included and divided into two groups based on the use of warfarin: No group (no warfarin prescriptions (n = 4009)), and Warfarin group (warfarin prescriptions (n = 820)). Results: Cox regression analyses revealed that the hazard ratio for all-cause mortality in the Warfarin group was 1.15 (p = 0.005) in univariate analysis and 1.11 (p = 0.047) in multivariable analysis compared to that of the No group. Hemorrhagic stroke was significantly associated with warfarin use, but no significant association between the use of warfarin and ischemic stroke or cardiovascular events was observed. The subgroup results demonstrated similar trends. Conclusions: Warfarin use is associated with a higher risk of all-cause mortality and hemorrhagic stroke, and has a neutral effect on ischemic stroke and cardiovascular events in patients with atrial fibrillation who are undergoing HD, compared to those who are not using warfarin.

The use of a low-flux hemo-dialyzer is associated with impaired platelet aggregation in patients undergoing chronic hemodialysis

In patients with chronic hemodialysis (HD), both abnormal thrombotic and bleeding events are commonly observed. Uremic platelet dysfunction is one of the important attributing factors. Moreover, HD may also result in aggregation dysfunction of platelets during the therapeutic procedure. However, how the HD process affects platelet and coagulation function is unknown and dialyzer membrane flux could have an impact on it. We aimed to compare the impacts of low-flux and high-flux HD on the platelet function of patients undergoing chronic HD. This was a cross-sectional study conducted in the HD unit of E-Da hospital in Taiwan. A total of 78 patients with maintenance HD three times per week for more than one year, including 40 with high- and 38 with low-flux hemodialysis, were recruited. Their platelet functions were evaluated using an in vitro platelet function analyzer (PFA-100) before and after the HD session. Of the 78 patients undergoing HD, 60 (76%) had prolonged pre-dialysis collagen/epinephrine (CEPI) and collagen/adenosine diphosphate closure times. Those receiving low-flux dialyzer had a significant increase in CEPI closure time (pre-dialysis 212.3 ± 62.1 seconds. post-dialysis 241.5 ± 64.3 seconds, P = .01), but not collagen/adenosine diphosphate closure time, after HD. After adjusting confounding factors, only the low-flux dialyzer demonstrated an independent association with the prolonged CEPI closure time after HD therapy (odds ratio = 23.31, 95% CI: 1.94-280.61, P = .01). We observed that impaired platelet aggregation is prevalent in patients undergoing chronic HD. Therefore, the use of low-flux dialyzers may further worsen platelet aggregation after dialysis. Patients with uremic bleeding diathesis should take precautions. We suggest that further studies using flow cytometry should be conducted to explore the mechanism of dialysis flux and platelet activity during HD.

Role of Platelets in Chronic Kidney Disease

Platelet-dependent mechanisms for excessive clotting and bleeding in CKD remain undefined. Moreover, platelets' contribution to inflammation, and specifically to CKD, are equally elusive. To date, descriptions of changes in the functional properties of circulating platelets during CKD have provided confusing interpretations. Experimental approaches that can advance our understanding of platelet dysfunction in CKD are needed, and studies that provide mechanistic insights into the dynamic relationships between thrombosis, bleeding, and inflammation associated with CKD will be essential to improve clinical management and outcomes for this vulnerable population. This article summarizes existing literature characterizing platelets in CKD and identifies areas that need further investigation.

In Vitro Closure Times (PFA-100) Are Different Between Peritoneal Dialysis and Hemodialysis

INTRODUCTION

 Platelet dysfunction is not uncommon in patients with end-stage renal disease (ESRD). Type of renal replacement therapy may have an effect on platelet functions, which has not been well investigated. We evaluated in vitro closure time (CT) differences between peritoneal dialysis (PD) and hemodialysis (HD) patients using platelet function analyzer (PFA-100)and observed a significant difference between these renal replacement therapies.

METHODS

 Patients with ESRD undergoing PD (n = 24) or HD (n = 23) for more than 6 months were included. Blood samples for collagen/epinephrine (Col/EPI) and collagen/adenosine diphosphate (Col/ADP) measurements were obtained before HD at a mid-week session for HD patients and at an outpatient control time for PD patients.

RESULTS

 Three of 24 (12.5%) PD patients and 16 of 23 (69.5%) HD patients had prolonged PFA-100 Col/EPI, p< 0.001. Likewise, 4.2% of PD patients and 87.0% of HD patients had prolonged PFA-100 Col/ADP, p< 0.001. Moreover, the median times of PFA-Col/EPI and PFA-100 Col/ADP were significantly lower in PD patients compared with those of HD patients (p< 0.001). Multivariate analysis showed that the type of renal replacement was a risk factor for both elevated PFA-100 Col/ADP and PFA-100 Col/EPI after adjusted for platelets, hematocrit, and urea (p< 0.001).

CONCLUSIONS

 The type of renal replacement therapy may have an effect on in vitro CTs; therefore, studies including more patients with long-term follow-up are needed to investigate if the difference has any impact on clinical outcomes.

Kidney disease and venous thromboembolism: Does being woman make the difference?

The risk of venous thromboembolism (VTE) is increased across the spectrum of chronic kidney disease (CKD), from mild to more advanced CKD, and typically characterizes nephrotic syndrome (NS). VTE risk in patients with kidney disease may be due to underlying hemostatic abnormalities, including activation of pro-thrombotic factors, inhibition of endogenous anticoagulation systems, enhanced platelet activation and aggregation, and decreased fibrinolytic activity. The mechanisms involved differ depending on the cause of the kidney impairment (i.e. presence of NS or CKD stage). Sex and gender differences, as well as, environmental factors or comorbidities may play a modulating role; however, specific sex and gender data on this topic are still rare. The aim of the present review is to discuss the VTE risk associated with impairment of kidney function, the potential mechanism accounting for it and the impact of sex differences in this clinical setting.

Effects of increased von Willebrand factor levels on primary hemostasis in thrombocytopenic patients with liver cirrhosis

In patients with liver cirrhosis procoagulant and anticoagulant changes occur simultaneously. During primary hemostasis, platelets adhere to subendothelial structures, via von Willebrand factor (vWF). We aimed to investigate the influence of vWF on primary hemostasis in patients with liver cirrhosis. Therefore we assessed in-vitro bleeding time as marker of primary hemostasis in cirrhotic patients, measuring the Platelet Function Analyzer (PFA-100) closure times with collagen and epinephrine (Col-Epi, upper limit of normal ≤ 165 s) or collagen and ADP (Col-ADP, upper limit of normal ≤ 118 s). If Col-Epi and Col-ADP were prolonged, the PFA-100 was considered to be pathological. Effects of vWF on primary hemostasis in thrombocytopenic patients were analyzed and plasma vWF levels were modified by adding recombinant vWF or anti-vWF antibody. Of the 72 included cirrhotic patients, 32 (44.4%) showed a pathological result for the PFA-100. They had mean closure times (± SD) of 180 ± 62 s with Col-Epi and 160 ± 70 s with Col-ADP. Multivariate analysis revealed that hematocrit (P = 0.027) and vWF-antigen levels (P = 0.010) are the predictors of a pathological PFA-100 test in cirrhotic patients. In 21.4% of cirrhotic patients with platelet count ≥ 150/nL and hematocrit ≥ 27.0%, pathological PFA-100 results were found. In thrombocytopenic (< 150/nL) patients with cirrhosis, normal PFA-100 results were associated with higher vWF-antigen levels (462.3 ± 235.9% vs. 338.7 ± 151.6%, P = 0.021). These results were confirmed by multivariate analysis in these patients as well as by adding recombinant vWF or polyclonal anti-vWF antibody that significantly shortened or prolonged closure times, respectively. In conclusion, primary hemostasis is impaired in cirrhotic patients. The effect of reduced platelet count in cirrhotic patients can at least be partly compensated by increased vWF levels. Recombinant vWF could be an alternative to platelet transfusions in the future.

Haemostasis in chronic kidney disease

The coagulation system has gained much interest again as new anticoagulatory substances have been introduced into clinical practice. Especially patients with renal failure are likely candidates for such a therapy as they often experience significant comorbidity including cardiovascular diseases that require anticoagulation. Patients with renal failure on new anticoagulants have experienced excessive bleeding which can be related to a changed pharmacokinetic profile of the compounds. However, the coagulation system itself, even without any interference with coagulation modifying drugs, is already profoundly changed during renal failure. Coagulation disorders with either episodes of severe bleeding or thrombosis represent an important cause for the morbidity and mortality of such patients. The underlying reasons for these coagulation disorders involve the changed interaction of different components of the coagulation system such as the coagulation cascade, the platelets and the vessel wall in the metabolic conditions of renal failure. Recent work provides evidence that new factors such as microparticles (MPs) can influence the coagulation system in patients with renal insufficiency through their potent procoagulatory effects. Interestingly, MPs may also contain microRNAs thus inhibiting the function of platelets, resulting in bleeding episodes. This review comprises the findings on the complex pathophysiology of coagulation disorders including new factors such as MPs and microRNAs in patients with renal insufficiency.

Platelet-Related Hemostasis before and after Hemodialysis with Five Different Anticoagulation Methods

Purpose

To evaluate platelet-related hemostasis during hemodialysis performed with five different anticoagulation methods.

Methods

31 chronic hemodialysis patients, 71% men, aged 57.5 ∓ 17.4 years, participated in our prospective study. Platelet function analyzer PFA -100 closure time (collagen/epinephrine -CEPI, collagen/adenosine diphosphate -CADP) was measured before and after hemodialysis, which was performed consecutively with five different anticoagulation methods: full-dose unfractionated heparin (UFH) and low-molecular weight heparin (LMWH): 31 patients, regional citrate anticoagulation (RCA): 28 patients, low-dose heparin: 25 patients and “heparin-free” dialysis: 9 patients. The degree of clotting in the dialysis system was graded on a 5 point scale.

Results

CEPI (mean ∓ SD, reference range 80-160 sec) before vs. after hemodialysis: UFH: 171.7 ∓ 62.1 vs. 170.8 ∓ 67.3; LMWH: 167.4 ∓ 56.9 vs. 159.4 ∓ 56.4; low-dose heparin: 175.3 ∓ 69.0 vs. 183.1 ∓ 60.5; RCA: 172.6 ∓ 57.4 vs. 161.6 ∓ 57.0; “heparin-free”: 181.7 ∓ 56.8 vs. 209.0 ∓ 66.5; all differences nonsignificant. CADP (mean ∓ SD, reference range: 68-121 sec) before vs. after hemodialysis: UFH: 132.0 ∓ 56.6 vs.146.3 ∓ 68.4; LMWH: 132.4 ∓ 57,0 vs. 123.1 ∓ 50.8; low-dose heparin: 137.2 ∓ 64.2 vs. 143.8 ∓ 55.5; RCA: 140.7 ∓ 48.2 vs. 132.9 ∓ 48.1; “heparin-free”: 137.1 ∓ 68.0 vs.139.2 ∓ 29.7; all differences nonsignificant. Before hemodialysis procedure CEPI was increased in 51.2% and CADP in 48.4% of the patients. The best dialysis system clotting score was found with UFH, LMWH and RCA.

Conclusions

Platelet dysfunction was demonstrated in approximately half of the chronic hemodialysis patients and was not improved after hemodialysis, regardless of the anticoagulation regimen used.

Prevalence and associations for abnormal bleeding times in patients with renal insufficiency

Platelet dysfunction and associated hemorrhagic complications are often encountered in patients with chronic kidney disease. This study aimed to evaluate the prevalence and associations for abnormal bleeding time (BT) in patients with renal dysfunction. Hemoglobin, hematocrit, platelet, blood urea nitrogen, creatinine, and parathyroid hormone levels were determined in 1716 patients (55.18 ± 17.19 years, men 50.8%). For these patients, BTs were estimated using a platelet function analyzer-100. Glomerular filtration rates (GFRs) were estimated using the Chronic Kidney Disease Epidemiology Collaboration equation. The study population was divided into six groups according to the estimated GFR (eGRF): group I, eGFR ≥ 90 ml/min/1.73 m(2); group II, 60 ≤ eGFR < 90 ml/min/1.73 m(2); group III, 30 ≤ eGFR < 60 ml/min/1.73 m(2); group IV, 15 ≤ eGFR < 30 ml/min/1.73 m(2); group V, eGFR < 15 ml/min/1.73 m(2); and group VI, undergoing regular hemodialysis. Renal insufficiency was defined as eGFR < 60 ml/min/1.73 m(2). To further investigate the role of inflammatory cytokines, nitric oxide (NO) and tumor necrosis factor alpha (TNF-α) were measured in a 327-patient subset of the total patient population (52.82 ± 18.3 years, men 60.9%). Abnormal BT occurred in 11.8% of group I, 15.3% of group II, 29.1% of group III, 37.5% of group IV, 35.0% of group V, and 32.1% of group VI. By Pearson correlation coefficient, eGFR (r = -0.089), hemoglobin (r = -0.127), platelet (r = -0.054) were correlated with BT. Multivariate analysis revealed that age [odds ratio (OR), 1.013; 95% CI, 1.004-1.022], renal insufficiency (eGFR < 60 ml/min/1.73 m(2); OR, 2.271; 95% CI, 1.672-3.083), anemia (hemoglobin < 120 g/l; OR, 1.486; 95% CI, 1.089-2.027), and thrombocytopenia (platelet < 150 × 10(9)/l; OR, 1.445; 95% CI, 1.089-1.918) were independently associated with prolonged BT. Plasma levels of NO and TNF-α were increased in patients with renal insufficiency (eGFR < 60 ml/min/1.73 m(2)). Plasma levels of NO in renal insufficiency group were higher in prolonged BT than those in normal BT. A significant positive correlation was noted between BTs and NO levels (r = 0.152, p = 0.009) but not with TNF-α levels. The prevalence of abnormal BTs was higher as eGFR declined. Old age, renal insufficiency, anemia, and thrombocytopenia were independent associations for abnormal BT.

Skin bleeding time for the evaluation of uremic platelet dysfunction and effect of dialysis

INTRODUCTION

In patients with chronic kidney disease (CKD) predisposition to bleeding is frequently seen due to disturbances in platelet adhesion and aggregation. Various tests have been utilized to evaluate the disturbance of hemostasis in end-stage renal disease patients. In this trial; we evaluated skin bleeding time in patients admitted to our hospital with uremic symptoms and having hemodialysis (HD) for the first time. We also examined the effects of HD and uremia on this test and investigated its effectiveness in predicting the hemorrhagic complications before implementation of invasive procedures in uremic patients.

MATERIAL-METHOD

Twenty nine patients (13 men,16 women; mean age 59.7 ± 18.1) with CKD who presented with symptoms of uremia and treated with HD for the first time were enrolled in this trial. The skin bleeding time were measured before initiation of first hemodialysis and after the second hemodialysis session.

RESULTS

The skin bleeding time after the second dialysis was significantly shorter when compared to pre-dialysis values (p < 0.05). Correlation analysis between the skin bleeding time and urea, creatinine, hemoglobin, platelet, and bicarbonate showed no correlation.

CONCLUSIONS

Skin bleeding time could reveal the uremic platelet dysfunction and beneficial effect of dialysis in the patients who presented with uremic symptoms and treated with HD for the first time. We suggest that skin bleeding time may be an appropriate test for the evaluation of hemostasis disturbance in uremic patients and prediction of the bleeding risk before invasive procedures.

Bleeding and thrombotic complications of kidney disease

With the rising prevalence of kidney disease, clinicians are increasingly faced with concerns about potential thrombotic and bleeding complications. Thrombotic risk, both arterial and venous, predominates with all severities of kidney disease but bleeding manifestations become an additional concern particularly with uraemia. This article reviews these contrasting problems and discusses strategies for prevention and management in the context of renal impairment, renal replacement therapy and renal transplantation.

Association between platelet-related hemostasis impairment and functional iron deficiency in hemodialysis patients

Hemostasis impairment and iron deficiency are relatively frequent in hemodialysis patients. Both conditions may contribute to anemia. The aim of our study was to explore possible associations between hemostasis impairment and iron deficiency by employing recently introduced methods for measurement of both conditions. Sixty-three hemodialysis patients were studied, with 30 age-matched, healthy controls. Hemostasis impairment was detected by in vitro closure time tests (collagen/epinephrine cartridge: CEPI; collagen/adenosine diphosphate (ADP) cartridge: CADP), whereas (functional) iron deficiency was measured by reticulocyte hemoglobin content (CHr) and the percentage of hypochromic red cells (HRC). We found that the patient group (N=14) with functional iron deficiency (CHr<29) had significantly delayed in vitro closure times in comparison to the patients (N=49) without functional iron deficiency. Furthermore, both types of closure time (CEPI and CADP) correlate highly significantly with CHr (P=0.002, and P=0.001). Such an association was not observed between in vitro closure time and HRC. We found a significant correlation between hemostasis impairment (measured by in vitro closure time) and iron deficiency (measured by CHr) in hemodialysis patients. This correlation has not previously been reported. It seems that in hemodialysis patients the hemostasis impairment affects (functional) iron deficiency, most likely by facilitating excessive blood loss and consequent iron deficiency. Thus, it appears that a delayed in vitro closure time along with decreased CHr may identify hemodialysis patients who suffer (occult) blood loss and/or excessive blood loss during hemodialysis procedure. The clinical value of this finding should be tested in larger studies.

Diagnostic performance of the platelet function analyzer (PFA-100®) for the detection of disorders of primary haemostasis in patients with a bleeding history–a systematic review and meta-analysis

The Platelet Function Analyzer (PFA-100) is increasingly being used in the workup of patients with a bleeding diathesis. A profound knowledge of the possible diagnostic performance of this test is essential in order to make sound clinical decisions based on its results. It was the aim of this study to systematically review the published literature and provide valid estimates of the diagnostic performance of the PFA-100 for detecting disorders of primary haemostasis in newly presenting patients with a bleeding diathesis. A comprehensive literature search was performed for studies published between January 1994 and February 2006. Studies were eligible for the systematic review if they provided data supposed to be applicable to the determination of the diagnostic performance of the PFA-100. Furthermore, they were included in a meta-analysis if study reporting allowed calculation of sensitivity and specificity and if study quality ensured minimized biases of these estimates for the described clinical setting. Pooled weighted sensitivity, specificity and diagnostic odds ratio were calculated applying random effects modelling and constructing summary operator characteristic curves. This was done separately for the available test modifications using either collagen/epinephrine (PFA-EPI) or collagen/adenosine-diphosphate (PFA-ADP) for platelet activation. Thirty-six articles were included in the systematic review. Six studies met our eligibility criteria for a meta-analysis. The major reason for exclusion from the meta-analysis was a case-control design. A total of 1486 and 1259 patients were included in the meta-analysis of the diagnostic performance of the PFA-EPI and PFA-ADP, respectively. Pooled weighted sensitivity and specificity of the PFA-EPI/PFA-ADP in detecting a disorder of primary haemostasis were: 82.5/66.9% (95%-confidence interval (95%-CI): 76.0-88.9%/57.9-75.9%), and 88.7/85.5% (95%-CI: 84.3-93.1%/82.0-89.1%). 83/75% of patients with a positive PFA-EPI/PFA-ADP result do have a disorder of primary haemostasis whereas 88/79% with a negative PFA-EPI/PFA-ADP result do not. The PFA-EPI appeared to have a higher sensitivity and better predictive values than the PFA-ADP in detecting disorders of primary haemostasis, although a rigorous gold standard definition for a disorder of primary haemostasis, particularly for platelet disorders, was not applied in most studies. The majority of the studies lacked important requirements for quality and reporting, precluding a more precise and definitive characterization of the clinical utility of the PFA-100. This emphasizes the need for an evidence-based critical appraisal of diagnostic studies in haemostasis research in order to promote the conducting of studies that produce clinically relevant results.

The effect of uremia on platelet contractile force, clot elastic modulus and bleeding time in hemodialysis patients

INTRODUCTION

Uremic bleeding frequently occurs in dialysis patients. Although its mechanism is not well characterized, acquired platelet dysfunction has been implicated in its pathogenesis. Skin bleeding time has been used to characterize platelet dysfunction in this population. However, the bleeding time is prone to error. The goal of this study was to compare the bleeding time to the novel platelet function parameters platelet contractile force and clot elastic modulus as well as platelet aggregation studies in controls and patients receiving maintenance hemodialysis.

MATERIALS AND METHODS

Forty-five subjects completed this study (25 controls, 20 dialysis). All subjects had the Ivy skin bleeding time procedure performed, as well as the collection of whole blood samples for the determination of platelet contractile force, clot elastic modulus, % von Willebrand Factor antigen, and platelet aggregation studies. Pearson's correlation determined the relationships between skin bleeding time and platelet function and clot structure parameters and markers of renal dysfunction.

RESULTS

Bleeding time was significantly prolonged in the dialysis group relative to controls. The platelet function parameters were not significantly different between groups. There was a significant relationship between bleeding time and creatinine concentration, however, no relationship existed between bleeding time and platelet function parameters.

CONCLUSIONS

Skin bleeding time poorly correlates with measurements of platelet function. There were no significant differences noted in platelet function between the groups despite the prolongations in bleeding time in the dialysis group. These data may suggest that the bleeding time reflects perturbations in platelet adhesion or secretion, and not aggregation. Further study is needed to characterize platelet function in dialysis patients.