Monitoring Unfractionated Heparin Treatments. Stability of Plasma Anti-Xa Activity up to 4 Hours in Citrated Tubes

Background: Unfractionated heparin (UFH) has been in clinical use for more than half a century. Monitoring UFH treatments is mandatory due to large inter- and intra-individual variations in its anticoagulant activity, with a risk of thrombosis in case of under-dosing and a risk of hemorrhage in case of over-dosing. Laboratory monitoring of UFH treatments is usually based on the prolongation of activated partial thromboplastin time (aPTT), or on the measurement of plasma anti-Xa activity. As UFH present in the patient's blood sample could be neutralized by platelet factor 4 (PF4) released by in-vitro activated platelets, it is recommended to perform the tests aimed at evaluating its anticoagulant activity as soon as possible after blood collection. Actually, the current guidelines recommend a maximum delay of 2 hours between blood sampling and testing for anti-Xa activity or aPTT prescribed for monitoring treatments by UFH, when blood is collected into citrated tubes. As such a short delay could be an issue, particularly for multisite centres, we evaluated the potential impact of a longer delay on test results. Design of the study: For that purpose, 2 citrated evacuated tubes containing 0.109 M tri-Na citrate (1 vol./9 vol.) were collected from patients on UFH: one was centrifuged and tested within 1h after blood collection (T1h) and one was stored for 4h at room temperature (+22°C) before being centrifuged and immediately analyzed (T4h). Methods: Anti-Xa activity was evaluated using 2 reagents: Biophen Heparin LRT (Hyphen Biomed, Neuville-sur-Oise, France) and HemosIL Liquid Heparin (Instrumentation Laboratory, IL, Bedford, MA, USA). aPTT was evaluated using the HemosIL SynthASil reagent (IL). All assays were automated on an ACL TOP 700 CTS (IL). As the distributions of the data were not found to be normal, anti-Xa and aPTT results were expressed as the median values (with ranges), and comparison of test results obtained at T1h and T4h performed using the Wilcoxon test. Test results were also compared according to Bland-Altman. Results: A total of 123 paired tubes were investigated. Analytical comparison of anti-Xa activity demonstrated a significant decrease (p<0.0001) after a 4 h-storage at room temperature (T4h) vs. a <1h-delay (T1h), for the two evaluated reagents (Table). The mean bias between test results obtained at T4h and T1h, evaluated according to Bland and Altman, was <0.05 IU/mL (in absolute value) for the two reagents, and identical for anti-Xa activities below or above 0.50 IU/mL. Such a value was below the imprecision of the techniques. There were 12 cases of discrepancy as whether test results were within the therapeutic range (0.30 - 0.70 IU/mL) or not when evaluated at T4h vs. T1h using the Hyphen reagent (9.8%), and 12.9% with the IL reagent. In most cases, these discrepancies were found for anti-Xa activities close to the lower limit of the therapeutic range, and would not have induced any change in the management of anticoagulation in these patients. APTT was significantly shortened (p<0.0001) after a 4h- vs. a 1h-storage at room temperature, with a mean bias of -8.1 sec, corresponding to a -0.25 decrease in ratio [relative change of -12.1% (95%CI= -34.8 +10.6)]. If considering the aPTT therapeutic range corresponding to anti-Xa activity between 0.30 and 0.70 IU/ml, 29 cases of discordant test results (23.6%) were observed that could have induced changes in the management of anticoagulation in 10% of the patients. Finally, the concordance whether test results measured at T4h and T0 were within or outside the therapeutic range was excellent for anti-Xa activity (kappa=0.813) and good for aPTT (kappa=0.661). Conclusions: These results suggest that extending to 4h the delay between blood sampling and measurement of anti-Xa activity prescribed for monitoring UFH treatments when blood is collected into citrated tubes is acceptable and safe, at least when evaluated with the two tested reagents. As change in aPTT results was found to be of a greater order of magnitude and more relevant, it could be justified recommending a shorter delay. Table Disclosures No relevant conflicts of interest to declare.

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Disruption of PF4/Hep Multimolecular Complex Assembly Using a Minimally Anticoagulant Heparin (ODSH)

Blood ◽

10.1182/blood.v116.21.723.723 ◽

2010 ◽

Vol 116 (21) ◽

pp. 723-723

Author(s):

Manali Joglekar ◽

Pedro Quintana ◽

Stephen Marcus ◽

Jian Liu ◽

Gowthami M. Arepally

Keyword(s):

Complex Formation ◽

Electrostatic Interactions ◽

Conflicts Of Interest ◽

Anticoagulant Activity ◽

Neutralization Assay ◽

Cross Reactivity ◽

Antibody Binding ◽

Fixed Amount ◽

Platelet Factor ◽

Molar Ratios

Abstract Abstract 723 Recent studies indicate that multimolecular complexes of platelet factor 4 (PF4) and heparin (H) are central to the pathogenesis of Heparin-Induced Thrombocytopenia (HIT). PF4/H multimolecular complexes are recognized preferentially by HIT antibodies (Rauova, Blood 2005) and are potently immunizing in a murine immunization model (Suvarna, Blood 2005). Because PF4/H multimolecular complexes assemble through non-specific electrostatic interactions, we hypothesized that disruption of PF4/H charge-dependent interactions could reduce immune mediated complications. To test this hypothesis, we employed a minimally anticoagulant compound (2-O, 3-O desulfated heparin, or ODSH, ParinGenix, Inc.) and characterized the charge-dependent interactions of murine PF4 (mPF4), ODSH and unfractionated heparin (UFH). In chromogenic assays of thrombin (IIa) generation, UFH was >80-fold more potent than ODSH in inactivating heparin (IC50 of residual IIa generation for UFH=3.1 nM v. ODSH= 259 nM, (Figure 1A). However, when equimolar amounts of UFH or ODSH (1.7 mM) were tested in a PF4 neutralization assay (Saggin, Thrombosis and Haemostasis 1992), the amount of mPF4 required to neutralize 50% of the anticoagulant activity of ODSH (IC50) was 25μg/mL, as compared to 73μg/mL for UFH (~3-fold difference), indicating that charge-dependent interactions, but not anticoagulant activity, were preserved between PF4 and ODSH (Figure 1B). When ODSH was added at 2.5, 5 or 10 fold molar excess to a fixed amount of UFH (6nM) in the PF4 neutralization assay, a proportionate increase in the amount of PF4 was needed to neutralize UFH, indicating that ODSH promotes the anticoagulant effect of UFH through preferential binding of PF4. To further characterize the biophysical interactions of PF4, ODSH and UFH, we used spectrophotometry and zeta potential to study the multimolecular complex formation (Suvarna, Blood 2007). We noted that mPF4 and ODSH formed multimolecular complexes at molar ratios of 2:1, whereas mPF4 and UFH complexes occurred at molar ratios of 1:1. When increasing concentrations of ODSH were added to pre-formed PF4/H multimolecular complexes, we noted a decrease in absorbance with increasing amounts of ODSH, indicating disruption of PF4/H multimolecular complexes (Figure 1C). However, when increasing amounts of UFH was added to preformed PF4/ODSH multimolecular complexes, a plateau in signal was noted, suggesting a higher affinity of ODSH for PF4. In PF4/H immunoassays, incubation of ODSH (1μg/mL) with HIT antibodies was effective in reducing antibody binding by >50% as compared to wells without ODSH. HIT antibodies did not recognize hPF4 (10mg/mL) in complex with ODSH (0.4-3.2 mg/mL), indicating minimal cross-reactivity of HIT antibodies with PF4/ODSH complexes (Figure 1D). In summary, we show that ODSH, a minimally anticoagulant heparin, can disrupt PF4/H multimolecular complex formation through charge dependent interactions and interfere with HIT antibody binding. These studies suggest that manipulation of PF4:H charge interactions can be a potential therapeutic strategy in the management of HIT. Disclosures: No relevant conflicts of interest to declare.

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Monitoring Treatments with Unfractionated Heparin: CTAD Must Be Used Instead of Citrate as the Anticoagulant Solution When Using Partial-Draw Collection Tubes.

Blood ◽

10.1182/blood.v114.22.2091.2091 ◽

2009 ◽

Vol 114 (22) ◽

pp. 2091-2091

Author(s):

Pierre A. Toulon ◽

Lién Abecassis ◽

Motalib Smahi ◽

Catherine Ternisien

Keyword(s):

Unfractionated Heparin ◽

Platelet Activation ◽

Conflicts Of Interest ◽

Vitamin K Antagonists ◽

Heparin Therapy ◽

Factor V ◽

Test Results ◽

Coagulation Testing ◽

Coagulation Tests ◽

Routine Coagulation

Abstract Abstract 2091 Poster Board II-68 Collecting small volumes of blood may be necessary, particularly in pediatrics, or in case of difficult or recurrent sampling. The aim of this multicenter study, involving four hemostasis laboratories, was to compare hemostasis test results in plasma samples obtained using partial- and full-draw evacuated polymer collection tubes containing 0.109 M sodium citrate (1 vol./9 vol.) as the anticoagulant solution (VenoSafeTM, Terumo Europe, Leuven, Belgium). For that purpose, blood was collected into one full- and one partial-draw tube from patients on vitamin K antagonists (VKA, n=100), unfractionated heparin (UFH, n=89), or a low molecular weight derivative (LMWH, n=52), as well as from 136 untreated patients, including 13 hemophiliacs. Routine coagulation tests i.e. PT/INR, aPTT, fibrinogen, and factor V, as well as factor VIII and anti-FXa activity when applicable, were measured using the routine techniques at each participating center. In addition, plasma PF-4 level, evaluated using an ELISA, was investigated in a subset of 36 healthy controls. In untreated patients incl. hemophiliacs as well as in those on either VKA or LMWH, no significantly relevant discrepancy (Bland-Altman) was found between tests results obtained using full- and partial-draw tubes. In contrast, anti-FXa activity in patients on UFH was significantly lower in partial- than in full-draw tubes [median=0.33 IU/mL (range: 0.00-1.11) vs. 0.39 (range: 0.05-1.32) respectively, p<0.0001]. Similarly, aPTT was significantly shorter in partial- than in the full-draw tubes, whereas other test results were not significantly different in the two tubes. That discrepancy was likely to be related to higher amount of PF4 released in plasma after increased platelet activation in partial-draw than in full-draw tubes [392 U/mL (range: 138-971) vs. 177 (range: 52-460) respectively, n=36; p<0.005)]. To further support that hypothesis, blood was collected, from 101 patients on UFH and from 104 untreated patients, into one partial-draw collection tube containing CTAD, a mixture of citrate and inhibitors of platelet activation, as the anticoagulant solution and one full-draw citrated tube, obtained from the same manufacturer. Comparison performed according to Bland-Altman of anti-FXa obtained in the two tubes failed to demonstrate any relevant difference, with a mean bias of +0.02 IU/mL that was identical throughout the measuring range of values [median=0.22 IU/mL (range: 0.06-1.16) vs. 0.20 (range: 0.03-1.15) respectively, n=101]. Moreover, in those patients on UFH, aPTT and other routine coagulation tests were not significantly different in the two tubes and the same applied to test results obtained in the plasma from untreated patients. These results suggest that samples collected into partial-draw citrated tubes allow accurate routine coagulation testing in all patients but those requiring UFH assessment, in which their use could lead to a significant underestimation of anticoagulation. In such cases, partial-draw tubes containing CTAD could be validly used to monitor heparin therapy, as well as to perform routine coagulation testing. Disclosures: No relevant conflicts of interest to declare.

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Heparin-Induced Thrombocytopenia Testing: ELISA Based Anti-Platelet Factor 4 Polyspecific and IgG-Specific Antibody Detection Assays Compared to the Unfractionated Heparin Serotonin Release Assay

Blood ◽

10.1182/blood-2021-145373 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3209-3209

Author(s):

Edward C.C. Wong ◽

Laura A. Worfolk ◽

Caixia Bi ◽

Lina J. Noh ◽

Andrew Espinoza ◽

...

Keyword(s):

Unfractionated Heparin ◽

Specific Antibody ◽

Serotonin Release ◽

Test Results ◽

Platelet Factor ◽

Heparin Induced Thrombocytopenia ◽

Specific Antibodies ◽

Functional Assays ◽

Antibody Assays ◽

Release Assay

Abstract Introduction: Antibodies that cause heparin-induced thrombocytopenia (HIT) can be detected with either antigenic or functional assays. Previously, it has been shown that antigenic (ELISA based) assays that detect anti-platelet factor 4 (anti-PF4) IgG, IgM, or IgA (polyspecific) antibodies are more sensitive but less specific than functional assays such as the unfractionated serotonin release assay (UFH SRA), and that the use of anti-PF4 assays that detect IgG antibodies only, would increase the specificity but decrease the sensitivity of these assays for the detection of HIT antibodies that are prothrombotic (associated with positive functional assay). To date large epidemiologic studies have not confirm these findings. To evaluate the relative performance of anti-PF4 polyspecific and IgG-specific antibodies in their ability to detect prothrombotic HIT antibodies, we evaluated results of non-reflexive HIT panels that contained either anti-PF4 polyspecific or IgG-specific assays and unfractionated heparin serotonin release assays over an eight-year period at a U.S. reference laboratory. Methods: Test results for 2 HIT detection panels were compared: 1 panel had UFH SRA plus the polyspecific PF4 ENHANCED® assay (GTI Diagnostics, Waukesha, WI) and 1 panel had UFH SRA plus the IgG-specific Zymutest HIA IgG assay (Hyphen Biomed, France). Test results were from the last 4 years of use for each panel (2009 to 2012 for the polyspecific panel; 2017 to 2020 for the IgG-specific panel). UFH SRA was performed as described by Sheridan et al, (1986) with positivity defined as ≥20% serotonin release by low dose UFH and >50% suppression of release at high dose (100 U/mL) UFH. For each year and assay, test results were stratified by optical density (OD) results, and the percent of results positive by UFH SRA was determined for each OD range. Median yearly UFH SRA positivity rates for each OD interval were compared for anti-PF4 polyspecific vs IgG-specific antibody assays using non-parametric statistical testing, Mann-Whitney U test, two-tailed, with significance defined as <0.05. Results: HIT panels with either ELISA based assays detecting either anti-PF4 polyspecific or IgG specific antibodies demonstrated increasing UFH SRA positivity rates as OD increased. Approximately 50% UFH SRA positivity occurred when OD was in the 2.000 to range. No significant differences in SRA positivity were seen at any positive OD interval when comparing anti-PF4 polyspecific vs IgG-specific assays. A small but significant difference was seen when OD results were considered This observation may have been due to a in the review process (2017-2020): when a UFH SRA result was positive with a negative OD result, repeat UFH SRA testing was performed. Conclusions: Our study demonstrates that the correlations of UFH SRA positivity and OD measurements are similar for anti-PF4 IgG-specific and polyspecific antibody assays. These results suggest the assay types may perform similarly for the detection of HIT and importantly provide important predictive information as to when an optical density value will lead to a positive UFH SRA result. Figure 1 Figure 1. Disclosures Wong: Quest Diagnostics: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Worfolk: Quest Diagnostics: Current Employment. Bi: Quest Diagnostics: Current Employment. Noh: Quest Diagnostics: Current Employment. Espinoza: Quest Diagnostics: Current Employment. Wu: Quest Diagnostics: Current Employment. Sahud: Quest Diagnostics: Current Employment. Racke: Quest Diagnostics: Current Employment. Dlott: Quest Diagnostics: Current Employment.

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Dermatan Sulfate and LMW Heparin Enhance the Anticoagulant Action of Activated Protein C

Thrombosis and Haemostasis ◽

10.1055/s-0037-1614856 ◽

1999 ◽

Vol 82 (11) ◽

pp. 1462-1468 ◽

Cited By ~ 22

Author(s):

José Fernández ◽

Jari Petäjä ◽

John Griffin

Keyword(s):

Molecular Weight ◽

Unfractionated Heparin ◽

Protein C ◽

Dermatan Sulfate ◽

Anticoagulant Activity ◽

Activated Protein C ◽

Factor V ◽

Factor Va ◽

Anticoagulant Action

SummaryUnfractionated heparin potentiates the anticoagulant action of activated protein C (APC) through several mechanisms, including the recently described enhancement of proteolytic inactivation of factor V. Possible anticoagulant synergism between APC and physiologic glycosaminoglycans, pharmacologic low molecular weight heparins (LMWHs), and other heparin derivatives was studied. Dermatan sulfate showed potent APC-enhancing effect. Commercial LMWHs showed differing abilities to promote APC activity, and the molecular weight of LMWHs correlated with enhancement of APC activity. Degree of sulfation of the glycosaminoglycans influenced APC enhancement. However, because dextran sulfates did not potentiate APC action, the presence of sulfate groups per se on a polysaccharide is not sufficient for APC enhancement. As previously for unfractionated heparin, APC anticoagulant activity was enhanced by glycosaminoglycans when factor V but not factor Va was the substrate. Thus, dermatan sulfate and LMWHs exhibit APC enhancing activity in vitro that could be of physiologic and pharmacologic significance.

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Comparison of the Non-Specific Binding of Unfractionated Heparin and Low Molecular Weight Heparin (Enoxaparin) to Plasma Proteins

Thrombosis and Haemostasis ◽

10.1055/s-0038-1649639 ◽

1993 ◽

Vol 70 (04) ◽

pp. 625-630 ◽

Cited By ~ 71

Author(s):

Edward Young ◽

Benilde Cosmi ◽

Jeffrey Weitz ◽

Jack Hirsh

Keyword(s):

Molecular Weight ◽

Unfractionated Heparin ◽

Plasma Proteins ◽

Low Molecular Weight Heparin ◽

Specific Binding ◽

Anticoagulant Activity ◽

Factor Xa ◽

Low Molecular Weight ◽

Heparin Binding ◽

Fixed Amount

SummaryThe non-specific binding of anticoagulantly-active heparin to plasma proteins may influence its anticoagulant effect. We used low affinity heparin (LAH) essentially devoid of anti-factor Xa activity to investigate the extent and possible mechanism of this non-specific binding. The addition of excess LAH to platelet-poor plasma containing a fixed amount of unfractionated heparin doubled the anti-factor Xa activity presumably because it displaces anticoagulantly-active heparin from plasma proteins. Although dextran sulfates of varying molecular weights also increased the anti-factor Xa activity, less sulfated heparin-like polysaccharides had no effect. These findings suggest that the ability to displace active heparin from plasma protein binding sites is related to charge and may be independent of molecular size. In contrast to its effect in plasma containing unfractionated heparin, there was little augmentation in anti-factor Xa activity when LAH was added to plasma containing low molecular weight heparin (LMWH), indicating that LMWH binds less to plasma proteins than unfractionated heparin. This concept is supported by studies comparing the anticoagulant activity of unfractionated heparin and LMWH in plasma with that in buffer containing antithrombin III. The anti-factor Xa activity of unfractionated heparin was 2-fold less in plasma than in the purified system. In contrast, LMWH had identical anti-factor Xa activity in both plasma and buffer, respectively. These findings may be clinically relevant because the recovered anti-factor Xa activity of unfractionated heparin was 33% lower in plasma from patients with suspected venous thrombosis than in plasma from healthy volunteers. The reduced heparin recovery in patient plasma reflects increased heparin binding to plasma proteins because the addition of LAH augmented the anti-factor Xa activity. In contrast to unfractionated heparin, there was complete recovery of LMWH added to patient plasma and little increase of anti-factor Xa activity after the addition of LAH. These findings may explain why LMWH gives a more predictable dose response than unfractionated heparin.

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Clinical Evaluation of the Torq Zero Delay Centrifuge System for Decentralized Blood Collection and Stabilization

Diagnostics ◽

10.3390/diagnostics11061019 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1019

Author(s):

Kyungjin Hong ◽

Gabriella Iacovetti ◽

Ali Rahimian ◽

Sean Hong ◽

Jon Epperson ◽

...

Keyword(s):

Clinical Chemistry ◽

Blood Collection ◽

Test Results ◽

Sample Collection ◽

Rapid Separation ◽

Cell Counts ◽

Collection Device ◽

Precision Study ◽

Clinically Significant ◽

Blood Specimens

Blood sample collection and rapid separation—critical preanalytical steps in clinical chemistry—can be challenging in decentralized collection settings. To address this gap, the Torq™ zero delay centrifuge system includes a lightweight, hand-portable centrifuge (ZDrive™) and a disc-shaped blood collection device (ZDisc™) enabling immediate sample centrifugation at the point of collection. Here, we report results from clinical validation studies comparing performance of the Torq System with a conventional plasma separation tube (PST). Blood specimens from 134 subjects were collected and processed across three independent sites to compare ZDisc and PST performance in the assessment of 14 analytes (K, Na, Cl, Ca, BUN, creatinine, AST, ALT, ALP, total bilirubin, albumin, total protein, cholesterol, and triglycerides). A 31-subject precision study was performed to evaluate reproducibility of plasma test results from ZDiscs, and plasma quality was assessed by measuring hemolysis and blood cells from 10 subject specimens. The ZDisc successfully collected and processed samples from 134 subjects. ZDisc results agreed with reference PSTs for all 14 analytes with mean % biases well below clinically significant levels. Results were reproducible across different operators and ZDisc production lots, and plasma blood cell counts and hemolysis levels fell well below clinical acceptance thresholds. ZDiscs produce plasma samples equivalent to reference PSTs. Results support the suitability of the Torq System for remotely collecting and processing blood samples in decentralized settings.

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Effect of Substrate Plate Heating on the Microstructure and Properties of Selective Laser Melted Al-20Si-5Fe-3Cu-1Mg Alloy

Materials ◽

10.3390/ma14020330 ◽

2021 ◽

Vol 14 (2) ◽

pp. 330

Author(s):

Pan Ma ◽

Pengcheng Ji ◽

Yandong Jia ◽

Xuerong Shi ◽

Zhishui Yu ◽

...

Keyword(s):

Room Temperature ◽

Internal Stresses ◽

Test Results ◽

Laser Melting ◽

Microstructure And Properties ◽

Uniform Microstructure ◽

Heat Treated ◽

Fine Microstructure ◽

Plate Heating ◽

Substrate Plate

The Al-20Si-5Fe-3Cu-1Mg alloy was fabricated using selective laser melting (SLM). The microstructure and properties of the as-prepared SLM, post-treated SLM, and SLM with substrate plate heating are studied. The as-prepared SLM sample shows a non-uniform microstructure with four different phases: fcc-αAl, eutectic Al-Si, Al2MgSi, and δ-Al4FeSi2. With thermal treatment, the phases become coarser and the δ-Al4FeSi2 phase transforms partially to β-Al5FeSi. The sample produced with SLM substrate plate heating shows a relatively uniform microstructure without a distinct difference between hatch overlaps and track cores. Room temperature compression test results show that an as-prepared SLM sample reaches a maximum strength (862 MPa) compared to the heat-treated (524 MPa) and substrate plate heated samples (474 MPa) due to the presence of fine microstructure and the internal stresses. The reduction in strength of the sample produced with substrate plate heating is due to the coarsening of the microstructure, but the plastic deformation shows an improvement (20%). The present observations suggest that substrate plate heating can be effectively employed not only to minimize the internal stresses (by impacting the cooling rate of the process) but can also be used to modulate the mechanical properties in a controlled fashion.

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Saphenous vein puncture for blood sampling of the mouse, rat, hamster, gerbil, guineapig, ferret and mink

Laboratory Animals ◽

10.1258/002367798780599866 ◽

1998 ◽

Vol 32 (4) ◽

pp. 364-368 ◽

Cited By ~ 169

Author(s):

Annelise Hem ◽

Adrian J. Smith ◽

Per Solberg

Keyword(s):

Saphenous Vein ◽

Blood Sampling ◽

Blood Collection ◽

Rapid Sampling

A method is described for blood collection from the lateral saphenous vein. This enables rapid sampling, which if necessary can be repeated from the same site without a need for new puncture wounds. The method is a humane and practical alternative to cardiac and retro-orbital puncture, in species where venepuncture has traditionally been regarded as problematic.

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Cryogenic Interlaminar Properties of PBO Fiber/Epoxy Composites

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.391-392.1445 ◽

2011 ◽

Vol 391-392 ◽

pp. 1445-1449

Author(s):

Chun Hua Zhang ◽

Shi Lin Luan ◽

Xiu Song Qian ◽

Bao Hua Sun ◽

Wen Sheng Zhang

Keyword(s):

Liquid Nitrogen ◽

Room Temperature ◽

Liquid Nitrogen Temperature ◽

Epoxy Composites ◽

Bending Test ◽

Test Results ◽

Sem Images ◽

Three Point Bending ◽

Pbo Fiber ◽

Interlaminar Shear

The influences of low temperature on the interlaminar properties for PBO fiber/epoxy composites have been studied at liquid nitrogen temperature (77 K) in terms of three point bending test. Results showed that the interlaminar shear strength at 77 K were significantly higher than those at room temperature (RT). For the analysis of the test results, the tensile behaviors of epoxy resin at both room temperature and liquid nitrogen temperature were investigated. The interface between fiber and matrix was observed using SEM images.

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Moving to e-bidding

Journal of Financial Management of Property and Construction ◽

10.1108/jfmpc-05-2018-0025 ◽

2019 ◽

Vol 24 (1) ◽

pp. 2-18 ◽

Cited By ~ 1

Author(s):

Djoen San Santoso ◽

Nuttapon Bourpanus

Keyword(s):

Wilcoxon Test ◽

Test Results ◽

Public Infrastructure ◽

Senior Managers ◽

Content Type ◽

Thai Government ◽

Infrastructure Project ◽

The Difference ◽

Public Money ◽

Mean Differences

Purpose This study aims to examine the influences of shifting the bidding system of Thai public infrastructure projects from e-auction to e-bidding. Design/methodology/approach A questionnaire survey was conducted with owners or senior managers with direct responsibility in deciding the mark-up of 72 small and medium-sized contractor firms. Five senior professionals were interviewed to provide insights into and to strengthen the discussion of the findings. The Wilcoxon test was applied to analyze the difference in the importance of the factors between e-auction and e-bidding. Findings The results revealed a shift in the importance of the factors, from those related to the financial aspects in the e-auction to the situational aspects in the e-bidding. The comparison test results also suggested that the majority of factors become significantly less important in the e-bidding system, with “identity of competitors” and “general expense of the bidding process” having the most apparent mean differences. The interview results supported by data on winning prices and estimations strongly indicated that bid collusions likely exist in the e-auction. By shifting to e-bidding, the data also show that the Thai Government can save public money in its infrastructure project development. Originality/value The study provides an analysis from the perspectives of contractor firms on how e-auction and e-bidding options influence bid mark-up decisions. Many studies have focused on the issues and advantages provided by the e-procurement mainly from the owner (government)’s perspective but how the change influences the contractor’s attitude has been less explored.

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