Platelet Closure Time Research Articles

Enhanced platelet function through CAR-T cell therapy in relapsed/refractory multiple myeloma

The influence of chimeric antigen receptor T (CAR-T) cell therapy on platelet function in relapsed/refractory (R/R) multiple myeloma (MM) has not been thoroughly investigated. Our cohort comprised fifty MM patients treated with CAR-T cells. The mean platelet closure time (PCT) induced by collagen/adenosine diphosphate (CADP) in peripheral blood was significantly prolonged before lymphodepletion (195.24 ± 11.740 s) and notably reduced post-CAR-T cell therapy (128.02 ± 5.60 s), with a statistically significant improvement (67.22, 95% CI 46.91–87.53, P < 0.001). This post-treatment PCT was not significantly different from that of healthy controls (10.64, 95% CI 1.11–22.40, P > 0.05). Furthermore, a pronounced enhancement in PCT was observed in patients with a response greater than partial remission (PR) following CAR-T cell infusion compared to pre-treatment values (P < 0.001). An extended PCT was also associated with a less favorable remission status. In patients with cytokine release syndrome (CRS) grades 0–2, those with a PCT over 240.5 s exhibited a shorter progression-free survival (PFS), with median PFS times of 10.2 months for the PCT > 240.5 s group versus 22.0 months for the PCT ≤ 240.5 s group. Multivariate analysis revealed that a PCT value exceeding 240.5 s is an independent prognostic factor for overall survival (OS) in R/R MM patients after CAR-T cell therapy. The study demonstrates that CAR-T cell therapy enhances platelet function in R/R MM patients, and PCT emerges as a potential prognostic biomarker for the efficacy of CAR-T cell therapy.

The hemostatic profile of cold-stored whole blood from non-greyhound and greyhound dogs over 42 days

To compare the hemostatic characteristics of cold-stored whole blood (CSWB) from non-greyhound dogs (NGD) and greyhound dogs (GD) over 42 days of storage, notably, platelet closure time (PCT) (NGD only), manual platelet count (PLT) (GD only), ellagic acid (INTEM) and tissue factor activated (EXTEM) rotational thromboelastometry, prothrombin (PT) and activated partial thromboplastin time (aPTT), fibrinogen concentration (FIB), and the activities of factors (F) FII, FV, FVII, FVIII, FIX, FX, FXIII antigen (FXIII:Ag), and von Willebrand factor antigen (vWF:Ag). Whole blood from 10 NGD and 10 GD, was refrigerated in CPD blood bags at 4°C for 42 days. Blood was analyzed before refrigeration (day 0) and at day 1 (d1), 3, 5, 7, 10, 14, 17, 21, 24, 28, 31, 35, 38, and 42. Multivariate linear mixed effects models were created to evaluate coagulation parameters over time and compare NGD and GD. Data are summarized as estimated marginal means with 95% confidence intervals. Significance was set at P < 0.05. The PCT for all NGD CSWB was above the device limit by d7. The PLT for GD CSWB did not change during storage. The mean alpha-angle for INTEM and EXTEM decreased to <50% of baseline at d38 and d31 for NGD, and d31 and d17 for GD CSWB. The mean maximum clot firmness (MCF) for INTEM and EXTEM reduced to <50% of baseline at d42 and d28 for both GD and NGD. PT and aPTT for NGD and GD increased over time. For NGD CSWB, the mean FVIII and vWF:Ag activities decreased to <50% of baseline at d7 and d28, respectively, and FIB reached 0.982 g/dL by d24. For GD CSWB, FVIII, FXIII:Ag and FV activities decreased to <50% of baseline by d3, d38, and d38, respectively, and FIB was 0.982 g/dL at baseline. Alpha-angle and MCF for both INTEM and EXTEM, and activities for FII, FV, FIX, FXIII:Ag were significantly lower, and vWF:Ag was significantly higher overall in GD CSWB compared with NGD. A significant difference in the pattern of change over time was detected between NGD and GD in EXTEM alpha-angle, INTEM and EXTEM MCF, FII, and FVIII activities. The in vitro viscoelastic parameters of GD and NGD CSWB declines over 42 days, but numerous hemostatic parameters (INTEM and EXTEM alpha-angle and MCF, activity of FII, FV, FV, FVII, FIX, FX, FXIII:Ag, vWF:Ag, and FIB) remain within 50% of baseline for more than 14 days. CSWB from GD compared to NGD has reduced hemostatic activity overall, but a similar pattern of decline for most parameters over time.

Hemostatic Responses to Multiple Bouts of Firefighting Activity: Female vs. Male Differences in a High Demand, High Performance Occupation.

While the fire service has long been a male-dominated occupation, women’s participation in this strenuous, high risk, high performance activity has increased in recent years. Firefighting induces significant cardiovascular strain, including hemostatic disruption; however, the effect of sex on hemostatic responses has not been investigated despite evidence that there are sex-related differences in hemostatic variables at rest and following exercise. Thus, we investigated hemostatic responses in age- and BMI-matched male and female firefighters who performed 3–4 evolutions of firefighting drills over a 3 h period. Venous blood samples were collected before and after the firefighting training drills and hemostatic variables were assessed. Firefighting significantly increased platelet count and factor VIII, tissue plasminogen activator (t-PA) antigen, and t-PA activity, and decreased activated partial thromboplastin time and plasminogen activator inhibitor (PAI-1) activity. Females had lower values for epinephrine-induced platelet closure time, antithrombin III, PAI-1 activity, and PAI-1 antigen. There were no interactions between sex and time for any variables assessed. In conclusion, multiple bouts of firefighting activity resulted in a procoagulatory state. Although there were sex differences for several hemostatic variables, male and female firefighters did not differ in their hemostatic response to multiple bouts of firefighting.

Clopidogrel resistance in elderly hospitalized patients detected by platelet closure time

Clopidogrel resistance in elderly hospitalized patients detected by platelet closure time

Influence of long-stay jugular catheters on hemostatic variables in healthy dogs.

To compare hemostatic variables performed on blood samples obtained from indwelling jugular catheters or direct venipuncture over a 72-hour period. Prospective experimental study. University research laboratory. Five healthy neutered male purpose-bred Beagle dogs. Each dog was sedated to facilitate placement of a long-stay 20-Ga polyurethane IV catheter into the jugular vein. Blood samples were obtained from the preplaced catheters at 4 time points corresponding to 0, 24, 48, and 72hours relative to placement. Blood samples were also obtained by direct venipuncture of a peripheral vein using a 21-Ga butterfly catheter and evacuated blood tubes at the same time points. Platelet count, platelet closure time, prothrombin time, activated partial thromboplastin time, fibrinogen, and kaolin-activated thromboelastography were performed on these paired samples at each time point. The patency of the indwelling catheters was maintained by flushing every 6hours with heparinized saline. No significant differences were identified in any of the hemostatic variables obtained by either blood collection technique at any time point during the study (P>0.05). There was also no significant day-to-day variation in any catheter-derived hemostatic variable obtained from individual dogs identified over the course of the study. These data suggest that accurate hemostatic variables may be obtained using blood collected from indwelling jugular catheters, maintained with heparinized saline for at least 72hours, in healthy dogs.

Clinical Significance of Platelet Closure Time in Patients with Multiple Myeloma

To explore the clinical significance of platelet closure time (PCT) in patients with multiple myeloma (MM). Peripheral blood samples of 50 newly diagnosed MM patients treated in our hospital from July 2018 to November 2019 and 34 healthy persons underuent physical at the same time were collected. PCT induced by collagen/epinephrine (CEPI) and collagen/adenosinediphosphate (CADP) in peripheral blood were detected by PFA-200，and the clinical data included age, sex, leukocyte count, hemoglobin level, platelet count and level of serum creatinine, cystatin c, blood calcium, β2-microglobulin (β2-MG), bone marrow plasma cells, light chain protein, as well as the MM types, ISS stage of patients were collected. The level of PCT in MM patients was significantly higher than that in healthy persons; the level of PCT were significantly increased with the increasing of ISS stage in newly diagnosed MM patients; After chemotherapy with bortezomib/dexamethasone (BD), the level of PCT in 15 patients who were responded to the treatment was significantly lower than those before treatment. The platelet closure time is abnormal in MM patients, moreover, relates to the progress of the disease. It has an important clinical significance for the evaluation of diagnostic stage and therapeutic efficacy evaluation of MM patients.

The effect of high-flux hemodialysis and post-dilution hemodiafiltration on platelet closure time in patients with end stage renal disease.

We aimed to compare prospectively the effect of high-flux hemodialysis and post-dilution hemodiafiltration on platelets. Twenty-two hemodialysis patients were treated with one high-flux hemodialysis and one post-dilution hemodiafiltration procedure. PFA-100 closure times (collagen/epinephrine-CEPI and collagen/adenosine diphosphate-CADP) were measured before and after the procedure, as well as platelet count, hemoglobin, hematocrit, and red blood cell count. All pre-dialysis and post-dialysis samples were taken from the afferent line. The platelet count after vs. before hemodialysis did not change significantly (229.3 ± 55.0 x109 /L vs. 233.6 ± 55.8 × 109 /L; P = 0.269), but was significantly lower after post-dilution hemodiafiltration (215.5 ± 51.7 × 109 /L vs. 245.3 ± 59.9 × 109 /L; P < 0.0001). CEPI after vs. before hemodialysis was not significantly prolonged (192.9 ± 60.8 s vs. 173.4 ± 52.5 s; P = 0.147), and the same applied to CADP (143.6 ± 40.3 s vs. 142.6 ± 38.4 s; P = 0.897). CEPI after vs. before post-dilution hemodiafiltration was significantly prolonged (268.3 ± 41.3 s vs. 176.4 ± 54.0 s; P < 0.0001) as was CADP (221.0 ± 53.9 s vs.133.9 ± 31.1 s; P < 0.0001). Only after post-dilution hemodiafiltration, we found a lower platelet count and prolonged platelet closure times.

Hypocoagulability and Platelet Dysfunction Are Exacerbated by Synthetic Colloids in a Canine Hemorrhagic Shock Model.

Background: Hemorrhagic shock and volume replacement can alter coagulation. Synthetic colloids, hydroxyethyl starch (HES), and gelatin, may enhance hypocoagulability. Our primary objective was to describe the effect of four fluid products on coagulation in canine hemorrhagic shock. Our secondary objective was to compare measurements of coagulation during shock to baseline in all dogs.Methods: Anesthetized greyhounds subjected to atraumatic hemorrhage for 60 min were administered 20 mL kg−1 of either fresh whole blood (FWB), 6% HES 130/0.4, 4% succinylated gelatin (GELO), or 80 mL kg−1 of isotonic crystalloid over 20 min (n = 6 per group). Platelet closure time (PCT), rotational thromboelastometry (ROTEM) and plasma coagulation assays were measured at baseline, end of hemorrhage (shock), and 40 (T60), and 160 (T180) min after study fluid. ROTEM parameters included clotting time (CT), clot formation time (CFT), alpha angle, maximum clot firmness (MCF), lysis index at 60 min (LI60), and thrombodynamic potential index (TPI) for INTEM, EXTEM, FIBTEM (MCF only), and APTEM (LI60 only) profiles. Plasma coagulation assays included prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen concentration and activities of factor VII (FVII), factor VIII (FVIII), and von Willebrand Factor antigen (vWF). Between-group differences were tested using linear mixed models with post-hoc between-group comparisons (Bonferroni-Holm corrected). Differences between baseline and shock were tested using paired t-tests. Significance was set at P < 0.05.Results: GELO showed longer PCT at T60, compared with FWB and CRYST, and at T180, compared with all other groups. HES showed longer EXTEM CT at T60, compared with all other groups. HES showed lower INTEM and EXTEM MCF at T60 and lower INTEM MCF at T180, compared with FWB. Some plasma coagulation assays showed greater hypocoagulability with HES. Comparing shock to baseline, EXTEM CT, INTEM CFT, EXTEM CFT, PT, and FVIII significantly increased and PCT, INTEM CT, INTEM MCF, EXTEM MCF, EXTEM LI60, EXTEM TPI, FIBTEM MCF, APTT, fibrinogen, FVII, and vWF significantly decreased.Conclusions: In dogs with hemorrhagic shock, volume replacement with GELO caused mild platelet dysfunction and HES was associated with coagulation changes consistent with hypocoagulability, beyond effects of hemodilution. Shock alone produced some evidence of hypocoagulability.

Platelet function and activation in Cavalier King Charles Spaniels with subclinical chronic valvular heart disease.

OBJECTIVE To assess platelet closure time (CT), mean platelet component (MPC) concentration, and platelet component distribution width (PCDW) in dogs with subclinical chronic valvular heart disease. ANIMALS 89 Cavalier King Charles Spaniels (CKCSs) and 39 control dogs (not CKCSs). PROCEDURES Platelet count, MPC concentration, PCDW, and Hct were measured by use of a hematology analyzer, and CT was measured by use of a platelet function analyzer. Murmur grade and echocardiographic variables (mitral valve regurgitant jet size relative to left atrial area, left atrial-to-aortic diameter ratio, and left ventricular internal dimensions) were recorded. Associations between explanatory variables (sex, age, murmur grade, echocardiographic variables, platelet count, and Hct) and outcomes (CT, MPC concentration, and PCDW) were examined by use of multivariate regression models. RESULTS A model with 5 variables best explained variation in CT (R(2), 0.74), with > 60% of the variance of CT explained by mitral valve regurgitant jet size. The model of best fit to explain variation in MPC concentration included only platelet count (R(2), 0.24). The model of best fit to explain variation in PCDW included platelet count and sex (R(2), 0.25). CONCLUSIONS AND CLINICAL RELEVANCE In this study, a significant effect of mitral valve regurgitant jet size on CT was consistent with platelet dysfunction. However, platelet activation, as assessed on the basis of the MPC concentration and PCDW, was not a feature of subclinical chronic valvular heart disease in CKCSs.

Platelet closure time in anesthetized Greyhounds with hemorrhagic shock treated with hydroxyethyl starch 130/0.4 or 0.9% sodium chloride infusions.

To measure platelet closure time (PCT) in dogs during controlled hemorrhagic shock and after fluid resuscitation with hydroxyethyl starch (HES) 130/0.4 or 0.9% sodium chloride. Experimental interventional study. University veterinary teaching hospital. Eleven healthy Greyhounds. Dogs were anesthetized and had 48 mL/kg of blood removed to induce hemorrhagic shock. Dogs received 20 mL/kg of HES 130/0.4 (n = 6) or 80 mL/kg of 0.9% sodium chloride (NaCl; n = 5) intravenously over 20 minutes. PCT was measured using the Platelet Function Analyzer-100 with collagen and adenosine-diphosphate cartridges at: T0 = 60 minutes after induction of anesthesia prior to hemorrhage, T1 = during hemorrhagic shock, and T2 = 40 minutes after completion of fluid bolus. Packed cell volume and platelet count were concurrently measured. Hemorrhagic shock did not significantly change PCT, with no difference between T0 and T1. Both the HES 130/0.4 and 0.9% NaCl group had a significantly increased mean PCT at T2 of 91.4 seconds (95% CI 69.3-113.4) and 95.5 seconds (95% CI 78.2-112.8), respectively, compared to T1. The magnitude of change was significantly greater for the 0.9% NaCl group than the HES 130/0.4 group. There was no difference in the magnitude of change in PCV and platelet count between the 2 groups. The PCV and platelet count were >25% and >100,000/μL, respectively, in all dogs, except for dogs in the HES 130/0.4 group at T2 where platelet counts were <100,000/μL. Controlled hemorrhagic shock in Greyhounds under anesthesia did not cause a significant change in PCT. Both HES 130/0.4 and 0.9% NaCl administration after induction of shock increased PCT. These results do not support that HES 130/0.4 causes relevant platelet dysfunction beyond hemodilution.

A Randomized Controlled Trial of Aspirin and Exertional Heat Stress Activation of Platelets in Firefighters during Exertion in Thermal Protective Clothing

Purpose. Platelet aggregation is enhanced in firefighters following short bouts of work in thermal protective clothing (TPC). We sought to determine if aspirin therapy before and/or following exertion in TPC prevents platelet activation. Methods. In a double-blind, placebo-controlled study, 102 firefighters were randomized to receive daily therapy (81 mg aspirin or placebo) for 14 days before and a single dose (325 mg aspirin or placebo) following exercise in TPC resulting in four potential assignments: aspirin before and after exercise (AA), placebo before and after exercise (PP), aspirin before and placebo after exercise (AP), and placebo before and aspirin after exercise (PA). Platelet closure time (PCT) was measured with a platelet function analyzer before the 2-week treatment, after the 2 week treatment period, immediately after exercise, and 30, 60, and 90 minutes later. Results. Baseline PCT did not differ between groups. PCT changed over time in all four groups (p < 0.001) rising to a median of >300 seconds [IQR 99, 300] in AA and >300 [92, 300] in AP prior to exercise. Following exercise, median PCT decreased to in all groups. Median PCT returned to >300 seconds 30 minutes later in AA and AP and rose to 300 seconds in PA 60 minutes after exercise. Conclusions. Daily aspirin therapy blunts platelet activation during exertional heat stress and single-dose aspirin therapy following exertional heat stress reduces platelet activation within 60 minutes. Key words: firefighter; uncompensable heat stress; thermoregulation; emergency incident rehabilitation

Effects of in vitro hemodilution of canine blood on platelet function analysis using the PFA‐100

The platelet function analyzer (PFA)-100 is a point-of-care instrument previously evaluated in humans and dogs. In both species, artificially prolonged platelet closure time (CT) occurs with anemia. Reliability of the analyzer in dogs becomes a concern when the HCT is between 0.25 and 0.35 L/L. The objective of this study was to further define the level of HCT at which CT is prolonged, using in vitro diluted canine blood. Citrated whole blood samples were collected from 22 healthy dogs. Initial HCT was determined and autologous platelet-rich plasma was added to samples to achieve HCTs of 0.33, 0.30, and 0.27 L/L. CT was determined in duplicate on the PFA-100 using collagen/adenosine-5'-diphosphate cartridges. Compared with the initial CT in samples with HCT 0.39-0.54 L/L (CT mean+/-SD=57.8+/-5.75 seconds), significantly prolonged CTs were found in hemodiluted samples with HCT 0.33 L/L (61.1+/-4.64 seconds), 0.30 L/L (64.3+/-6.79 seconds), and 0.27 L/L (70.8+/-7.90 seconds) (P=0.029; repeated measures ANOVA). Although statistical differences were found, further studies are needed to determine the clinical significance of the mild prolongation in CT associated with mild anemia. Until then, dogs with HCTs slightly <0.35 L/L should be evaluated cautiously for platelet dysfunction using the PFA-100.

The effect of Hetastarch (670/0.75) in vivo on platelet closure time in the dog

To evaluate the effect of 6% hydroxyethyl starch (HES) solution in vivo, with an average molecular weight of 670 kDa and degree of substitution of 0.75, on canine platelet function. Prospective, controlled-experimental study. University of California, Davis, Veterinary Medical Teaching Hospital. Seven healthy employee-owned dogs. Seven dogs were included in the treatment group. Four of these dogs also served as the control group. Platelet closure time (CT) was measured using a platelet function analyzer and collagen/ADP cartridges. Dogs were given 20 mL/kg of either sodium chloride 0.9% (control group, n=4) or HES (treatment group, n=7) IV over 1 hour. CT was measured before the infusion, and at 1, 3, 5, and 24 hours after the start of the infusion. There was a significant change over time from 0 to 24 hours (P<0.001), a significant difference between groups across time (P<0.001), and a significant group-by-time interaction (P=0.007). At 3 hours, mean CT for the treatment group was 122.3+/-18.1 seconds, which was significantly different (P<0.001) from the control group (71.0+/-3.5 s). At 5 hours, mean CT for the treatment group was 142.7+/-33.9 seconds, which was significantly different (P=0.001) from the control group (75.0+/-8.6 s). Mean CT at 24 hours was within the reference interval for both the control and treatment group (66.0+/-2.9 and 81.8+/-11.9 s, respectively); however, CT in 3 individual dogs in the treatment group at this time point remained prolonged. A clinically relevant dose of HES 670/0.75 prolongs CT in dogs for up to 24 hours. This may be due to platelet dysfunction in addition to the effects of hemodilution, and therefore, may increase the risk of bleeding.

Clinical and laboratory aspects of the Aspirin-like defect as hereditary thrombocytopathy

The Aspirin-like defect (ALD) is caused by defects in the intraplatelet arachidonic acid (AA)-metabolism. We here present the characteristics of a larger cohort in a single centre. Based on 17 ALD index patients bleeding symptoms, agonist-induced platelet aggregation and closure times in the PFA-100 test were analysed in a family cohort of altogether 52 individuals from 17 families. Absent aggregation to AA (maximal aggregation <or= 10%) was the main diagnostic criterion. A mild ALD was diagnosed when aggregation was 11-40%. In addition to 17 ALD index patients, 13 family members displayed ALD. 4 family members were diagnosed with a mild ALD. Epistaxis, easy bruising, menorrhagia and perioperative hemorrhage were the most common bleeding symptoms, whereas three quarters of ALD patients presented with >or=1 bleeding symptoms. In case of a bleeding tendency diagnostic procedures should rule out primary haemostatic defects. Hereditary platelet function defects including ALD are an important differential diagnosis. Family studies are reasonable.

INTRAVENOUS ADMINISTRATION OF CHOLINE OR CDP-CHOLINE IMPROVES PLATELET COUNT AND PLATELET CLOSURE TIMES IN ENDOTOXIN-TREATED DOGS

This study was performed to assess the effects of intravenous choline chloride and cytidine-5'-diphosphate choline (CDP-choline) treatments on circulating platelet, white blood cell, and red blood cell counts and platelet functions in response to endotoxin. Saline (0.2 mL/kg), choline chloride (20 mg/kg), or CDP-choline (70 mg/kg) were given intravenously three times at 4-h intervals, and endotoxemia was induced by endotoxin (E. coli 055:B5, 20 microg/kg) infusion, 5 min after the first treatment. Blood samples were collected before and at multiple time points after the challenge, for a panel of hematologic parameters and platelet closure times measured by PFA-100. In saline-treated dogs, circulating platelet counts decreased by 85% (P < 0.001) at 0.5 h and remained low by 36%-80% (P < 0.5-0.001) 1-12 h after endotoxin. Circulating WBC counts decreased by 80%-90% (P < 0.001) at 0.5-2 h, and increased (P < 0.001) by 190% 12 h after the endotoxin. In response to endotoxin, RBCs increased by 10%-13% (P < 0.05) at 1-12 h. Endotoxin-induced decline in circulating platelets was attenuated at 0.5 h (P < 0.05-0.01) and reversed at 1-12 h (P < 0.05-0.001) by choline. Platelet closure times were shortened from 81 +/- 10 s and 135 +/- 10 s to 29 +/- 5 s (P < 0.001) and 60 +/- 3 s (P < 0.001) at 0.5 h, and prolonged (P < 0.001) at 1-8 h after endotoxin induction. Endotoxin-induced shortening in platelet closure times was attenuated (P < 0.05) and blocked (P < 0.01) by choline and CDP-choline, respectively. These results showed that choline and CDP-choline treatments improved circulating platelet counts and platelet function during endotoxemia in dogs.