scholarly journals Acquired Platelet GPVI Dysfunction As Possible Predictor for Early Sepsis Diagnosis and Poor Outcome

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3609-3609
Author(s):  
Lukas J Weiss ◽  
Georgi Manukjan ◽  
Nils Nagler ◽  
Markus Kredel ◽  
Thien-Tri Lam ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Early Time ◽  
Bacterial Isolates ◽  
Vascular Integrity ◽  
Platelet Counts ◽  
Sepsis Diagnosis ◽  
Bona Fide ◽  
Early Sepsis

Introduction: Sepsis is a major contributor to the global disease burden with estimated 20 million cases per year. With every hour prior to begin of therapy mortality increases by over 7%. Hence, early diagnosis is indispensable for patient survival, though it is hampered by the lack of known pathognomonic symptoms. Sepsis diagnosis is set according to an increase of the sequential organ failure assessment (SOFA) score, reflecting organ dysfunction. Severe symptoms comprising dysfunctional hemostasis are disseminated intravascular coagulation and formation of massive edema due to loss of vascular integrity. Functional hemostasis and maintenance of vascular integrity depends particularly on the platelet surface receptor glycoprotein (GP)VI that dimerizes upon activation and transduces its signals via the associated immunoreceptor tyrosine activation motif (ITAM) of the Fc-gamma chain. Sepsis-associated thrombocytopenia has been extensively investigated and low platelet counts are implemented in the SOFA score.Platelet function during sepsis, however, remains ill-defined with few reports using ADP or thrombin receptor activating peptide (TRAP) and overall conflicting results. Objectives: We assessed platelet function in patients with sepsis III criteria in a single center study at three times during disease: (I) intensive care unit (ICU) admission day; (II) day five to seven at ICU; (III) day of ICU discharge. Methods: Fifteen patients were recruited from the ICU of the University Hospital Würzburg, Germany (m:f ratio 9:6; median age 70; mortality: 40%). Platelets in whole blood were stimulated with ADP, TRAP, or the GPVI agonist collagen-related peptide (CRP). Activation was detected flow cytometrically by P-selectin (CD62P) exposure and integrin GPIIb/IIIa activation (PAC-1 binding). Results were correlated with light transmission aggregometry (LTA) and immunoblotting of phospho-Syk and -LAT. Co-incubation experiments were performed with plasma, whole blood or patient-borne bacterial isolates comprising Gram-negative (E. coli, K. pneumoniae) or Gram-positive (E. faecalis) strains. Results: Platelet function was markedly reduced in all patients assessed by flow cytometry and LTA despite overall unaltered receptor expression. The defect was most prominent after GPVI stimulation with CRP(Mean Geo-MFI ± SD; Control: 9356 ± 3460; Sepsis: 1438 ± 2090; p<.0001). In 14/15 patients GPVI-dysfunction was already present at time (I). In contrast, only 7/15 patients were thrombocytopenic at this early time. We did not consistently find elevated GPVI ectodomain plasma levels, low platelet counts, increased mean platelet volume, or elevated reticulated platelet levels in our cohort at early time points and minor alterations only late during disease progression. We conclude that none of these is a bona fide biomarker, neither for early sepsis diagnosis nor as a prognostic marker. Sepsis platelets failed to transduce the GPVI signal to induce tyrosine phosphorylation of Syk kinase or LAT. ITIM receptor-based tyrosine phosphatases SHP1 and SHP2 were neither preactivated in resting platelets nor responsive to GPVI stimulation. Of note, platelet aggregation upon GPVI stimulation increased in those patients whose condition ameliorated. We found a strong correlation of restored platelet aggregation by LTA with survival and could distinguish survivors from non-survivors using this marker for stratification (%max aggregation ± SD; survivors: 25 ± 8%; non-survivors: 4 ± 3%; p<0.01). Responsiveness to CRP was unaltered when platelets of healthy donors were co-incubated with patient blood borne bacterial isolates. Platelet reactivity was also unaltered when they were pre-incubated in plasma of sepsis patients. However, pre-incubation in whole blood clearly diminished the response toward CRP,suggesting that the abrogated GPVI signaling is in part mediated by cellular components. Conclusion: Our results strongly imply that GPVI hypo-responsiveness could serve as a bona fide marker for early sepsis diagnosis and also bears potential to act as a prognostic indicator for therapy monitoring, independent from the source of infection. Acknowledgement: Financial support was granted by the Deutsche Forschungsgemeinschaft (374031971 - TRR 240). Disclosures No relevant conflicts of interest to declare.

Enhanced platelet aggregation and activation under conditions of hypothermia

2007 ◽  
Vol 98 (12) ◽  
pp. 1266-1275 ◽  
Author(s):  
Ruben Xavier ◽  
Ann White ◽  
Susan Fox ◽  
Robert Wilcox ◽  
Stan Heptinstall
Keyword(s):  
Cardiac Surgery ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Baseline Levels ◽  
Spontaneous Aggregation ◽  
High Concentrations ◽  
Induced Aggregation ◽  
P2y12 Antagonist

SummaryThe effects on platelet function of temperatures attained during hypothermia used in cardiac surgery are controversial. Here we have performed studies on platelet aggregation in whole blood and platelet-rich plasma after stimulation with a range of concentrations of ADP, TRAP, U46619 and PAF at both 28°C and 37°C. Spontaneous aggregation was also measured after addition of saline alone. In citrated blood, spontaneous aggregation was markedly enhanced at 28°C compared with 37°C. Aggregation induced by ADP was also enhanced. Similar results were obtained in hirudinised blood. There was no spontaneous aggregation in PRP but ADP-induced aggregation was enhanced at 28°C. The P2Y12 antagonist AR-C69931 inhibited all spontaneous aggregation at 28°C and reduced all ADP-induced aggregation responses to small, reversible responses. Aspirin had no effect. Aggregation was also enhanced at 28°C compared with 37°C with low but not high concentrations of TRAP and U46619. PAF-induced aggregation was maximal at all concentrations when measured at 28°C, but reversal of aggregation was seen at 37°C. Baseline levels of platelet CD62P and CD63 were significantly enhanced at 28°C compared with 37°C. Expression was significantly increased at 28°C after stimulation with ADP, PAF and TRAP but not after stimulation with U46619. Overall, our results demonstrate an enhancement of platelet function at 28°C compared with 37°C, particularly in the presence of ADP.

Rapid Assessment of Platelet Function Using Thromboelastography and Small Volumes of Citrated Whole Blood.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3995-3995 ◽  
Author(s):  
Fred G. Pluthero ◽  
Margaret L. Rand ◽  
Victor S. Blanchette ◽  
Walter H. Kahr
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Function Analysis ◽  
Maximum Amplitude ◽  
Ease Of Use ◽  
Platelet Response ◽  
Platelet Function Disorders ◽  
Wide Range

Abstract Platelet function disorders are a key cause of abnormal bleeding, and diagnosis is challenging because: platelet abnormalities are diverse, affecting many aspects of function; variability in platelet function testing in clinical laboratories makes it difficult to compare results; large blood volumes required for platelet function analysis make it difficult to perform in neonatal patients; manipulation of platelet rich plasma used for platelet aggregation can lead to test variability; platelet aggregation curves are difficult to interpret in thrombocytopenic patients. We describe a method of testing platelet function using citrated whole blood and thromboelastography (TEG) that overcomes some of these limitations. Commercially-available platelet mapping kits allow the effects of the platelet agonists adenosine diphosphate (ADP) and arachidonic acid (AA) to be assessed via a TEG assay where reptilase and activated factor XIII produce fibrin clots independent of thrombin in heparinized whole blood. The activation and aggregation of platelets is quantified by measuring the difference in maximum amplitude (MA) between unstimulated samples, which form weak fibrin-only clots, and samples with agonists added, which form stronger clots containing fibrin and activated/aggregated platelets. Platelet mapping was used as the basis for a TEG assay which can be used to assess platelet responses to a wide range of stimuli - including ADP, AA, epinephrine, collagen, U46619 (thromboxane-A2 receptor agonist), SFLLRN (PAR-1 thrombin receptor activating peptide) and AYPGKF (PAR-4 activating peptide) - in small samples (330μL) of citrated native (CN) blood or plasma to which heparin is added to a concentration of 20U/mL. Samples were recalcified by adding calcium chloride to 10mM (necessary for the function of reptilase and FXIIIa), and other reagent volumes were the same as in platelet mapping assays, with fibrin activator prepared at 1/2 regular strength. The concentrations of platelet agonists were: collagen 51μg/ml, epinephrine 0.27μM, ADP 5.4μM, arachidonic acid 135μg/mL, U46619 2.6μM, SFLLRN 6.76μM and AYPGKF 34μM. These concentrations produced TEG MA values in heparinated fibrin-activated CN blood from a panel of normal individuals comparable to those obtained from recalcified CN blood in the absence of heparin (the fibrin/platelet response control). The platelet response was rapid with maximum amplitudes reached within 10 minutes for all agonists except collagen, which required >30 minutes to produce maximum amplitude. We have found this TEG platelet-response assay to be useful in detecting platelet function abnormalities, producing results which correlate with and extend those of other platelet function tests. For example in one patient a weak response to epinephrine corresponded to similar platelet aggregation results, and in another the TEG assay detected a weak PAR-1 response not specifically detected in other tests. The assay has also proven useful in assessing platelet function in blood and plasma having low platelet concentrations (<50 x 10E9/L) from experimental or pathological causes (e.g. thrombocytopenia), in titrating platelet responses to agonists and in assessing the effects of antiplatelet agents in vivo and in vitro. Thus this TEG platelet function assay has the advantages of speed, ease of use, flexibility, adaptability to low platelet concentrations and sample economy, requiring small volumes of citrated blood which can be used for other coagulation assays and platelet response tests.

Influence of Nanopolymers with Different End-Functionalities on Platelet Function and the Coagulation Cascade - An Ex-Vivo Study.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4038-4038
Author(s):  
Meera Chitlur ◽  
Erin Ware ◽  
Sujata Kannan ◽  
Wendy Hollon ◽  
Steve Buck ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Aggregation ◽  
Surface Charge ◽  
Platelet Function ◽  
Whole Blood ◽  
Clot Formation ◽  
Coagulation Cascade ◽  
Cancer Drug ◽  
Dendritic Polymers ◽  
Drug Concentrations

Abstract Dendritic polymers are branched nanopolymers with a central core and multiple peripheral functional groups that offer great potential as high payload delivery vehicles carrying multiple copies of drug molecules, targeting ligands and imaging agents to their site of action. Their nanoscopic dimensions offer exciting possibilities for achieving high intracellular drug concentrations in many therapeutic areas including anti-cancer drug delivery. Biocompatibility and biodistribution of dendritic polymers may be influenced by surface charge and concentration. One of the major challenges in their use is the effect on coagulation. The objective of this study was to determine the effect of change in surface charge and concentration of dendritic polymer on cellular and enzymatic components of coagulation. Materials and Methods: The effect of increasing concentrations (1, 10, 100, and 1000mcg/ml) of polyamidoamine (PAMAM) dendrimers with -COOH (anionic), -OH (neutral), and -NH2 (cationic) end functionalities, on platelet function and coagulation was evaluated using thromboelastography, whole blood aggregation, and flow cytometry. The thromboelastographic profile and platelet aggregation studies were obtained on samples of whole blood incubated for thirty minutes with dendrimer. Platelets were incubated with FITC labelled dendrimer for 30,60 and 120 mins, to determine uptake and platelet activation using flow cytometry. All tests were performed in triplicate. RESULTS: Thromboelastography: No significant effect on clot formation (time to clot formation and size) was seen with PAMAM-COOH (COOH) or PAMAM-OH (OH). Prolonged time to initiation of clot and decreased size were noted with 100 and 1000mcg/ml of PAMAM-NH2(NH2) as shown in figure1, indicating impairment of both the enzymatic and cellular components of the coagulation system. Whole Blood Aggregation: Neither platelet aggregation nor secretion were significantly affected by COOH or OH. Platelet aggregation was significantly decreased with NH2 at 100 and 1000mcg/ml. Flow Cytometry: Spontaneous CD62 activation was seen in platelets incubated with NH2. No spontaneous CD62 activation was noted with COOH or OH even at 1000mcg/ml. Platelet uptake of FITC labeled dendrimer was assessed at 30, 60 and 120mins of incubation. Increased uptake of FITC labeled dendrimer was noted at 2 hours with NH2. TEG clotting Profiles with PAMAM-NH2. TEG clotting Profiles with PAMAM-NH2. CONCLUSIONS: Surface charge of the dendritic nanopolymers plays a significant role on its effect on coagulation and platelet function. The anionic -COOH terminated and neutral -OH terminated dendrimers had no effect on hemostasis even at the highest concentrations while the cationic-NH2 was associated with inhibition of platelet aggregation and delayed clot initiation at higher concentrations. This would indicate that the anionic and neutral dendrimers would serve as better vehicles than cationic dendrimers for targeted delivery of therapeutic agents.

Assessment of ADP-induced platelet aggregation with light transmission aggregometry and multiple electrode platelet aggregometry before and after clopidogrel treatment

2008 ◽  
Vol 99 (01) ◽  
pp. 121-126 ◽  
Author(s):  
Siegmund Braun ◽  
Stefan Jawansky ◽  
Wolfgang Vogt ◽  
Julinda Mehilli ◽  
Albert Schömig ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Light Transmission ◽  
Platelet Rich Plasma ◽  
Platelet Aggregometry ◽  
Light Transmission Aggregometry ◽  
Before And After ◽  
Standardized Method ◽  
Multiple Electrode

SummaryThe level of platelet aggregation, measured with light transmission aggregometry (LTA) in platelet rich plasma (PRP), has been shown to predict outcomes after percutaneous coronary intervention (PCI). However, measuring parameters of platelet function with LTA is time consuming and weakly standardized. Thus, a fast and standardized method to assess platelet function after clopidogrel treatment would be of great value for clinical practice. A new method, multiple electrode platelet aggregometry (MEA), to rapidly measure platelet aggregation in whole blood has recently been developed. The aim of this study was to assess parameters of platelet function with MEA and LTA before and after administration of 600 mg clopidogrel. Blood samples from 149 patients scheduled for coronary angiography were taken after clopidogrel treatment; in addition, in 60 of the patients samples were available before clopidogrel treatment. ADP-induced platelet aggregation was measured with LTA and simultaneously in whole blood with MEA on the Multiplate analyzer. Platelet aggregation measured with MEA decreased significantly after clopidogrel treatment (P<0.0001). ADP-induced platelet aggregation assessed with MEA and LTA correlated significantly (Spearman rank correlation coefficient=0.71; P<0.0001).The results of MEA, a fast and standardized method to assess the platelet response to ADP prior to and after clopidogrel treatment, correlate well with LTA.

Acquired platelet GPVI receptor dysfunction in critically-ill patients with sepsis

Blood ◽  
2021 ◽  
Author(s):  
Lukas Johannes Weiss ◽  
Georgi Manukjan ◽  
Annerose Pflug ◽  
Nadine Winter ◽  
Mathis Leonard Weigel ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Aggregation ◽  
Pilot Study ◽  
Animal Models ◽  
Disease Onset ◽  
Vascular Integrity ◽  
Sepsis Diagnosis ◽  
Syk Kinase ◽  
Healthy Donors ◽  
Icu Discharge

GPVI, the platelet immunoreceptor tyrosine activating motif (ITAM) receptor for collagen plays a striking role on vascular integrity in animal models of inflammation and sepsis. Understanding ITAM-receptor signaling defects in humans suffering from sepsis may improve our understanding of the pathophysiology, especially during disease onset. In a pilot study, platelets from fifteen septic patients were assessed consecutively at day of admission, day 5-7 and the day of ICU-discharge, and subjected to comprehensive analyses by flow cytometry, aggregometry and immunoblotting. Platelet function was markedly reduced in all patients. The defect was most prominent after GPVI stimulation with collagen-related peptide. In 14/15 patients GPVI-dysfunction was already present at time of ICU admission, considerably before the critical drop in platelet counts. Sepsis platelets failed to transduce the GPVI-mediated signal to trigger tyrosine phosphorylation of Syk kinase or LAT. GPVI deficiency was in part inducible in platelets of healthy donors through co-incubation in whole blood, but not in plasma from sepsis patients. Platelet aggregation upon GPVI stimulation increased only in those patients whose condition ameliorated. As blunted GPVI signaling occurred early at sepsis onset this defect could be exploited as an indicator for early sepsis diagnosis, which needs to be confirmed in prospective studies.

Comparison of Rapid Platelet Function Assay with Whole Blood Platelet Impedance Aggregometry for the Definition of Aspirin Resistance.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4018-4018
Author(s):  
Anna M. Dyszkiewicz-Korpanty ◽  
Anne Kim ◽  
James D. Burner ◽  
Eugene P. Frenkel ◽  
Ravindra Sarode
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Blood Platelet ◽  
Aspirin Resistance ◽  
Impedance Aggregometry ◽  
Definition Of ◽  
Induced Aggregation

Abstract The reported incidence of aspirin (ASA) resistance ranges from 5 to 30%. Various platelet function assays have been employed to detect aspirin resistance in patients with cardio- and cerebrovascular disease. Such a high proposed incidence of ASA resistance poses a critical need for a rapid point-of -care (POC) platelet function test. Unfortunately, no uniformly accepted definition of ASA resistance exists. Platelet aggregation studies that have been used to define ASA resistance are time consuming and require special technical expertise. The Ultegra Rapid Platelet Function -ASA (RPFA-ASA) has been developed as a POC test that is performed without sample processing. This optical method measures agglutination of fibrinogen-coated beads upon platelet activation with arachidonic acid. In the presence of aspirin effect, however, the agglutination of the beads is inhibited. The described cutoff of ≥ 550 Aspirin Reaction Units (ARU) is termed non-responsiveness to ASA based on a preclinical study and subsequent correlation with epinephrine-induced platelet aggregation in platelet rich plasma. Since RPFA-ASA uses whole blood, we validated its performance characteristics against a classic whole blood platelet aggregation assay (WBA). We studied 50 healthy volunteers, aged 25–75 (24 men, 26 women) with normal CBC, who had not ingested anti-platelet drugs for 14 days prior to the study. Baseline studies included WBA (dual channel aggregometer, Chrono-log Inc., Havertown, PA) using both arachidonic acid (AA -0.5; 0.25 mM) and collagen (1; 2 μg/mL) as well as an RPFA-ASA assay (Accumetrics Inc., San Diego, CA). These studies were repeated after 3 days of ASA (325 mg/d) intake. Based on a review of the literature, we defined an adequate ASA response as a completely inhibited AA-induced platelet aggregation and at least 30% inhibition of collagen-induced aggregation (both concentrations of the agonist). Thus, those with &lt; 30% inhibition of aggregation response to collagen were considered ASA resistant. Eleven subjects were ASA resistant by WBA (20%; 8 females and 3 males (aged 25–63). In contrast, since all 50 subjects achieved ARU values of &lt; 550 ARU, none were recognized as an ASA non-responder by the RPFA-ASA. While the current cutoff of &lt; 550 ARU posed by the Ultegra RPFA-ASA does identify those who have taken ASA, the assay is unable to recognize ASA non-responders. Thus, based on these data, the appropriate cutoff for the recognition of ASA resistance by the RPFA-ASA should be re-adjusted to a significantly lower level to ensure appropriate assay results.

Whole Blood Impedance Aggregometry: A New Tool for Severe Inherited Platelet Disorder Diagnosis?

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 5266-5266 ◽  
Author(s):  
Celine Desconclois ◽  
Vincent Valarche ◽  
Tewfik Boutekedjiret ◽  
Martine Raphael ◽  
Marie Dreyfus ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Von Willebrand Disease ◽  
Fast Method ◽  
Normal Ranges ◽  
Platelet Function Disorders ◽  
Platelet Disorder ◽  
Platelet Disorders ◽  
Von Willebrand

Abstract Abstract 5266 Diagnosis and characterization of platelet function disorders may be challenging. It requires multiple laboratory data including the assessment of platelet functions. Platelet function analysis is most commonly performed using light transmission aggregometry (LTA). LTA is a time-consuming method requiring centrifugation steps and large blood volumes. It is difficult to perform in children and in cases of thrombocytopenia. In contrast, platelet aggregation in whole blood using impedancemetry (WBI) is a fast method, allows omission of centrifugation steps and performance of platelet function studies under more physiological conditions with small samples size. It is based on the change of resistance proportional to the amount of platelets sticking to two electrodes where an alternating current is applied. Multiplate® (for “multiple electrode aggregometry”, Dynabite Medical) is a new generation of WBI aggregometer using diluted blood and single-use test cells containing twin electrodes that reduce the variation of results. We have already showed the good Multiplate® performance concerning ristocetin-induced platelet aggregation in a population of 30 patients with characterized von Willebrand disease (Valarche et al, 2011). Our aim in this ongoing study was to assess the performance of WBI in patients with inherited platelet function disorders. We tested 8 patients including 2 unrelated patients with Glanzmann Thrombasthenia (GT), 2 unrelated patients with Bernard-Soulier Syndrome (BSS), 1 patient with Gray Platelet Syndrome (GPS) and 3 patients from the same family with a platelet type von Willebrand disease (PTVWD). GT, BSS, and PTVWD diagnosis were confirmed using genotyping. BSS and GPS patients had chronic thrombocytopenia. GT, BSS, GPS and 1/3 PTVWD had platelet function tests with LTA in parallel. WBI was performed on heparinized whole blood diluted at ½ in NaCl at 37°C and triggered using high (0.77 mg/mL, WBI RH) and low (0.5 mg/mL, WBI RL) final ristocetin concentrations, ADP (6.5 Âμ Mol, WBI ADP) and collagen (3.2 Âμg/mL, WBI Coll). Results were expressed in arbitrary unit (AU) corresponding to the area under the aggregation curve observed during 6 min. Normal ranges indicated in brackets were based on the mean +/− 2 SD of 30 healthy volunteers' results. Results highlighted in grey are those out of the normal ranges (Table 1).Table 1:Results of the 8 patients with inherited platelet disorders.PatientsPlatelet count (109/L)WBI RH (AU) [>500]WBI RL (AU) [<150]WBI ADP (AU) [>550]WBI Coll (AU) [>500]GT 116923441443GT 224955417ND7BSS 134371119129BSS 230254733582GPS7916217ND42PTVWD22099493ND338PTVWD231116560ND1092PTVWD2341174168ND852 All patients except those with PTVWD had decreased results with WBI. However, as expected, patients with GT had flat traces using WBI ADP and WBI Coll but normal or only decreased curves (234 – 554 AU) using WBI RH. On the opposite, BSS patients had flat traces using WBI RH but detectable curves using WBI ADP (191 – 335 AU) despite decreased platelet count. The thrombocytopenic GPS patient has a flat trace using WBI Coll and decreased WBI RH (162 AU). Members of the PTVWD family had normal results except a slightly increased result with WBI RH in 1/3 patients. Finally, LTA results performed in 6/8 patients were all in accordance with those of the WBI. In conclusion, in 8 patients with well characterized inherited platelet disorders, WBI was able to detect all abnormalities except PTVWD. In such cases, different ristocetin concentrations use might be critical to increase sensitivity. In our hands, WBI was able to discriminate disorders involving platelet glycoprotein (GP) IIb-IIIa from GP Ib-IX-V: GT patients exhibited flat traces using WBI ADP and WBI Coll, whereas patients with BSS exhibited flat traces with ristocetin. These preliminary results need to be confirmed on a larger population of patients with various characterized platelet function disorders. They suggest that WBI using the Multiplate® analyzer, which is a fast, easy and blood-preserving test, could be a valuable extra step before or in addition to the classic LTA for the diagnosis of severe inherited platelet disorders. Disclosures: No relevant conflicts of interest to declare.

An evaluation of methods for determining reference intervals for light transmission platelet aggregation tests on samples with normal or reduced platelet counts

2008 ◽  
Vol 100 (07) ◽  
pp. 01-12 ◽  
Author(s):  
Karen A. Moffat ◽  
Menaka Pai ◽  
Yang Liu ◽  
Jodi Seecharan ◽  
Heather McKay ◽  
...  
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Light Transmission ◽  
Reference Intervals ◽  
Platelet Counts ◽  
Healthy Control ◽  
Parametric Analyses ◽  
Control Samples ◽  
Non Parametric

SummaryLight transmission platelet aggregation tests are important for diagnosing platelet function defects. However, uncertainties exist about the best procedures to determine aggregation reference intervals. We investigated methods for determining reference intervals for light transmission aggregation tests, using the % maximal aggregation values for prospectively collected data on healthy control samples. Reference intervals for samples tested at 250 x 109 platelets/l were determined by mean ± 2 standard deviations and non-parametric analyses. To establish reference intervals for tests on thrombocytopenic subjects, regression analyses were used to estimate 95% confidence limits for % maximal aggregation, according to sample platelet counts, using data for control samples diluted to match the platelet count of undiluted thrombocytopenic patient platelet-rich plasma samples. For samples tested at 250 x 109 platelets/l, non-parametric analyses described 95% of data for healthy control samples better than mean ± 2 standard deviations. For samples tested at lower counts, to match thrombocytopenic samples, the % maximal aggregation was influenced by platelet count and derived limits were wider at very low platelet counts for almost all agonists. With ristocetin, it proved feasible to test samples with very low platelet counts to exclude Bernard-Soulier syndrome and type 2B von Willebrand disease. Non-parametric analyses should be the preferred method to establish light transmission aggregation reference intervals for samples tested at normal platelet counts. The derived limits for thrombocytopenic samples provide guidance for evaluating thrombocytopenic platelet function disorders, including which agonists to test, based on the sample platelet count.

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