PT Tests Research Articles

Haematological Values for Children, Adults and Geriatrics in Nnewi and Environs, Anambra State, Nigeria

Background: Haematological parameters are very important in defining the health status of individuals. Hence availability of haematological reference ranges have been used as discriminators for individuals that are healthy or ill. Some independent factors such as age, gender, ethnicity, geographical location, lifestyle and method of assays are known to affect reference ranges, therefore in establishing reference ranges one must put these factors into consideration. Methodology: A cross sectional study was conducted in Nnewi and its environ, and a total of 1,947 subjects were selected for this study using stratified random method. Whole blood sample was collected in EDTA bottle and tri-sodium citrate bottle from each subject for the haematological parameters. Kruskal Wallis and Man-Whitney statistical tool were used for the multivariable and two variables analysis respectively, using SPSS version 21 software package. Result: Significant differences (p=0.00) were observed among the different age groups; the adults had Hb, PCV and RBC values higher when compared with that of the children and the geriatrics. PT and CT tests showed significantly lower values (p=0.00) in the adults when compared to the children and geriatrics. No significant differences (p=0.276) were seen among the children, adults and geriatrics in MCV, INR and BT. Conclusion: Some of the haematological parameters vary among the age groups; children, adults and geriatrics. The haematological values obtained from this study for children, adults and geriatrics, can serve as a reference values to guide health care providers in management of patients in Nnewi and its environ.

Preclinical evaluation of point‐of‐care prothrombin time as a biomarker test to guide prothrombin replacement therapy in coagulopathic bleeding

Summary Essentials Prediction of bleeding risk in trauma patients is difficult.We evaluated a test which measures prothrombin time/ability of blood to clot.We showed the prothrombin time test reflected prothrombin concentration in blood.The test could be used in trauma patients to identify those in need of prothrombin replacement. BackgroundHemorrhage is still a common cause of death in trauma. Central lab measured prothrombin time (lab PT) is predictive of low prothrombin concentration and clinical outcome in trauma patients, however, treatment guidance is limited by slow turnaround times. Here, we have preclinically evaluated the potential of a point‐of‐care prothrombin time test (POC PT) as a faster alternative to identify patients with low prothrombin concentration.MethodsHuman whole blood was serially diluted and prothrombin time measured by POC PT (CoaguChek XS Pro, Roche) and lab PT. Recombinant human prothrombin (MEDI8111) was added to human whole blood with or without depletion of prothrombin by pretreatment with prothrombin neutralizing antibodies.ResultsThere was no observable difference in the sensitivity of either test to dilution at blood volumes of 60‐100%. At blood volumes of ≤55% (equivalent to 47 mg/L prothrombin), PT sharply increased, with greater dilutional sensitivity observed in the POC test. Both tests were insensitive to prothrombin up to 194 mg/L added MEDI8111 (equivalent to 328 mg/L prothrombin versus endogenous concentration of 129 mg/L). Depletion of endogenous prothrombin inversely correlated with an increase in PT which returned to baseline following addition of 97 mg/L MEDI8111 or above. Both assays correlated well above 48.5 mg/L added MEDI8111 (65.9 mg/L prothrombin).ConclusionsOur data supports that POC PT tests, such as the CoaguChek XS Pro, are fit for purpose to confirm a coagulopathic threshold for prothrombin and provide a fast, simple, and mobile method to guide MEDI8111 therapy in bleeding trauma patients.

Discovery of novel aminobenzisoxazole derivatives as orally available factor IXa inhibitors

Using structure based drug design, novel aminobenzisoxazoles as coagulation factor IXa inhibitors were designed and synthesized. Highly selective inhibition of FIXa over FXa was demonstrated. Anticoagulation profile of selected compounds was evaluated by aPTT and PT tests. In vitro ADMET and pharmacokinetic (PK) profiles were also evaluated.

Hypercoaguable Work up : Are We Overtesting ?

BACKGROUNDHypercoaguable states are defined as a group of inherited or acquired conditions associated with predisposition to venous thromboembolism(VTE) , arterial thrombosis or both . Of the inherited thrombophilias , Factor V Leiden mutation(FVL) is the most common, with Prothrombin mutation G20210(PT) being the second most common cause, both being inherited as autosomal dominant.FVL is a single point mutation in the gene that codes for coagulation factor V. It renders factor V resistant to inactivation by activated protein C. Heterozygosity for Factor V Leiden occurs in 3-8% of the general US and European populations, homozygosity being very rare. Approximately 10% of FVL heterozygotes develop VTE over their lifetime. The relative risk for VTE is increased three to six fold in Factor V Leiden heterozygotes. PT is a single point mutation (G to A substitution at nucleotide 20210) in the prothrombin gene. This mutation appears to result in elevated concentration of plasma prothrombin. The overall prevalence is approximately 2%. Risk of VTE in individuals who are heterozygous for PT has been estimated to be increased approximately three- to fourfold. However , the relative risk of having one of these mutations in patients presenting with a first time VTE is 15-20% and 6% for FVL and PT respectively .Although these mutations increases the chances of VTE, its association with arterial thrombosis and obstetric complications( recurrent miscarriages , still birth, Intraueterine fetal demise) are not clear. Therefore testing for these mutations is appropriate only in patients with idiopathic VTE, younger patients and or those with family history , recurrent thrombosis , thrombosis in unusual vascular bed. In our institution ,there was a concern that appropriate selections of patients to test for these mutations was not occurring and the cost of inappropriate testing may be adding to the healthcare costs. We performed a retrospective review of indications for thrombophilia testing and its costs over a period of one year at our tertiary medical center. METHODSAll patients who had testing for FVL and PT from June 2015-June 2016 were identified by screening ordered tests done in the special coagulation laboratory. Inpatients and outpatients were included .The clinical data reviewed included age, sex and indication for the tests ordered.Overall cost was calculated for each group. RESULTSWe evaluated 144 patients . The mean age of patients was 51 years (range :7 Weeks - 88 years)Males constituted 51%(74/144), females were 49%(70/144) of the cohort.Both FVL and PT tests were ordered on all the patients.Of 144 patients , only 3 patients tested positive and were heterozygous for FVL and, 1 positive patient was heterozygous for PT.The cost of the test for FVL was $348 and for PT $267 in a standard laboratory. The following table lists the common indications for the tests ordered*Other included Lung transplant workup 10%, heart transplant work up9% , VAD thrombosis 1%, MI (0.9%) miscarriage 5% and other -10% The number of tests that did not meet the standard criteria for testing were103Only 28 % of testing was done for an appropriate indication (Unprovoked VTE , Recurrent VTE , VTE at an unusal site) Cost associated of unnecessary testing$63,345 CONCLUSIONTesting for inherited risk factors for VTE when not indicated by standard criteria leads to excess costs for patients and healthcare systems .Education of healthcare providers may limit unnecessary testing and ultimately reduce healthcare costs . [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Covalent Bonding of Heparin on the Crystallized Poly(lactic acid) (PLA) Membrane to Improve Hemocompability via Surface Cross-Linking and Glycidyl Ether Reaction.

The hemocompatibility of the dialysis membrane has been considered the key factor influencing the dialysis performance for curing the kidney malfunction. In this work, the commonly used anticoagulant heparin in the clinic was directly bonded to the poly(lactic acid) (PLA) membrane to improve the hemocompatibility via the glycidyl ether reaction. A novel precopolymer P(VP-VTES-GMA) was first prepared via free radical polymerization. The surface cross-linking of the precopolymer containing GMA segments enabled the membrane to anchor heparin through the glycidyl ether reaction. The chemical structure of the precopolymer was confirmed by 1H NMR. The surface chemistry was analyzed by XPS, toluidine blue staining, and solubility tests. The crystallization behavior, heat resistance, morphology, hydrophilicity, pore size, and pure water flux were investigated. The hemocompatibility was comprehensively investigated via APTT, PRT, PT, FIB, and platelet adhesion tests. The simulated dialysis performances relating to urea, creatinine, lysozyme, and BSA clearance were measured. All results demonstrated that the covalent bonding of heparin provided the PLA membrane with excellent hemcompatibility, hydrophilicity, heat resistance, and dialysis performance as well.

Identification of Casting Conditions Influence on the Structure and Properties of Al-Si-X Alloy Castings by Experimental and Virtual Way

The paper describes influence of the structure type and its parameters on the mechanical properties of cast products (not subjected to plastic forming), made out of Al-Si-X alloys. The special attention has been focused on the dendritic structure parameters: dendritic arms spacing of the first order (DAS 1) and the second order (DAS 2). The results of investigations of mechanical properties of the test castings made using three basic casting technologies: gravity sand casting (GSC), gravity die casting (GDC) and high pressure die casting (HPDC), are presented. All the castings were made out of the same AlSi9Cu3 alloy. The test castings (adherent samples and separately cast samples) were subjected to a static tensile test and their mechanical properties were determined. In the next stage, the samples fractures and zones near the fractures (metallographic specimen) were subjected to visual testing, penetrating testing PT and metallographic microscopic tests. The microstructure, including the size of the DAS 2, was determined. Evaluation of the porosity state was also undertaken. A customer casting was also manufactured and subjected to the metallographic, tomographic (CT) and strength tests. The castings solidification simulation tests were performed for all the three casting technologies (GSC, GDC and HPDC) using the Nova Flow &Solid system. The results were used for estimation of the correlation between the cooling rate of the particular casting solidifying in the above mentioned mould types and for the DAS size. The coupled influence of the structure parameters on the mechanical properties, regarding the occurrence of porosity, was also analyzed.

Silica Nanoparticles Effects on Blood Coagulation Proteins and Platelets.

Interaction of nanoparticles with the blood coagulation is important prior to their using as the drug carriers or therapeutic agents. The aim of present work was studying of the primary effects of silica nanoparticles (SiNPs) on haemostasis in vitro. We studied the effect of SiNPs on blood coagulation directly estimating the activation of prothrombin and factor X and to verify any possible effect of SiNPs on human platelets. It was shown that SiNPs shortened coagulation time in APTT and PT tests and increased the activation of factor X induced by RVV possibly due to the sorption of intrinsic pathway factors on their surface. SiNPs inhibited the aggregation of platelet rich plasma induced by ADP but in the same time partially activated platelets as it was shown using flow cytometry. The possibility of SiNPs usage in nanomedicine is strongly dependant on their final concentration in bloodstream and the size of the particles that are used. However SiNPs are extremely promising as the haemostatic agents for preventing the blood loss after damage.

Chitosan/gelatin composite sponge is an absorbable surgical hemostatic agent

Chitosan is a versatile biological material that is very well known for its hemostatic properties. The purpose of this study was to test the hemostatic properties of a chitosan composite obtained from silkworm pupae and gelatin. This spongy porous material was cross-linked with tannins and then freeze-dried under vacuum to obtain composites containing chitosan and gelatin in different proportions. Results showed that the best blood-clotting index (BCI) was achieved in vitro by a chitosan/gelatin sponge (CG) ratio of 5/5 (W/W). Furthermore, CG had the best hemostatic effect in rabbit artery bleeding and liver model tests compared to the two components separately. The better hemostatic effect of CG may be due to its ability to absorb blood platelets easily and to the higher liquid adsorption ratio. However, no obvious differences were observed in thrombin generation with both aPTT and PT tests. Cell toxicity tests with L929 cells showed that CG caused no obvious cytotoxicity. In addition, subcutaneous transplantation of CG into rabbits resulted in almost complete degradation of CG after 6 weeks, together with rich vascular generation and proliferation in the transplanted region. Thus, CG can be considered an effective absorbable hemostatic material.

Assessment of apixaban plasma levels by laboratory tests: suitability of three anti-Xa assays

While laboratory monitoring is not required in patients treated with apixaban, a direct factor-Xa inhibitor, assessment of its concentration is useful in some critical situations. However, few data are available on its effect on coagulation tests and on the suitability of anti-Xa assays for its quantification. It was the objective of this study to identify laboratory tests suitable for apixaban concentration assessment. Coagulation tests - PT and aPTT- and anti-Xa assays were performed in apixaban-spiked plasma samples. To evaluate the sensitivity of PT and aPTT to apixaban, we conducted a first monocenter part, with a wide range of concentrations (50-1,000 ng/ml), a large panel of reagents (20 reagents), and two coagulometers (STAR®, Stago and ACL TOP®, IL), and a second multicenter part involving 13 laboratories using either a common PT reagent (RecombiPlastin2G®) or the local PT and aPTT reagents. In the multicentre part, five blinded apixaban-spiked plasma samples (0/100/200/400/800 ng/ml - checked by HPLC-MS/MS) were used; apixaban concentrations were measured with three anti-Xa assays, apixaban calibrators and controls (Stago). PT and aPTT tests using a large panel of reagents displayed a low sensitivity to a wide range of apixaban concentrations. The concentrations to double PT ranged from 400 to >1,000 ng/ml with the 10 reagents. With the three anti-Xa assays, inter-laboratory precision and accuracy were below 11% and 12%, respectively. In conclusion, whereas PT and aPTT tests were not sensitive enough to detect apixaban, the three anti-Xa assays tested using lyophilised apixaban calibrators and controls allowed to reliably quantify a wide range of apixaban concentrations.

Comparative Studies Of Purified Poloxamer 188 Using ClotBased and Viscoelastic Measurements Of Coagulation

Background Poloxamer 188 (P188; Mast Therapeutics, Inc.) is a surface-active, non-ionic block copolymer which binds to hydrophobic surfaces on damaged cells improving membrane hydration and lowering adhesion and viscosity. It is known to improve microvascular function in various pathologic states. Currently, this agent is under investigation in a phase 3 clinical trial for treatment of sickle cell disease patients experiencing acute vaso-occlusive crisis. The effect of P188 on blood coagulation and platelet function has been evaluated in several clinical trials where no clinically significant effect has been observed. In these trials, coagulation studies were based on standard clot based methods (e.g., PT and aPTT) and did not include viscoelastic measurements such as thromboelastography (TEG). Given P188 alters viscosity, we compared the effect of this agent using various clotbased, chromogenic and viscoelastic measurements of blood coagulation. Materials and Methods Whole blood activated clotting time studies were carried out in groups of healthy individuals (n=10) at a concentration range of 1.872-15.0mg/mL. TEG analysis on native and citratedwhole blood was carried out on TEG 5000 (Haemoscope Corp, Niles, IL) at concentrations of 0-0.45 mg/mL. The effect of P188 on normal plasma clotting parameters, such as PT and aPTT, was measured at a concentration range of 0-10 mg/mL. The effect of P188 on thrombin-induced clot formation was investigated using a fibrinokinetic method. The effect of P188 on thrombin generation was measured using the fluormetric method (Technoclone, Vienna, Austria). The anti-protease effects of P188 were studied using chromogenic substrate methods using isolated biochemical systems. Results At concentrations up to 10 mg/mL, P188 did not produce any modification of Celiteactivated clotting time (Celite-ACT). At all concentrations the Celite-ACT values remained comparable to saline (138-140 sec for P188 vs. 140 sec for saline). In the TEG analysis, P188 produced a concentrationdependent hypocoagulant effect in both native and citratedblood as evidenced by increased angle and shortening of maximum amplitude (MA). In standard PT and aPTT tests, P188 did not produce any effect on the clotting profile at concentrations up to 20 mg/mL. In fibrinokinetic studies, P188 produced an increase in the fibrin clot density and rate of fibrin polymerization. Discussion These studies demonstrate that even at very high concentrations, P188 does not produce an effect on whole blood clotting as measured by the Celite-ACT assay; this result was confirmed in other standard assays. Fibrinokinetic studies revealed an increase in the rate of fibrin formation and clot density. However, at relatively low concentrations, P188 exhibited a hypocoagulant profile in TEG analysis. The marked discordance between TEG and other coagulation tests suggest that P188’s effect on viscosity and adhesive interactions result in an artifact in TEG analysis and an incorrect indication of a hypocoagulant effect. This effect may be due to the viscoelastic endpoint in the TEG assay. Further studies are needed to confirm this hypothesis. Disclosures: Fareed: Mast Therapeutics: Research Funding. Emanuele:Mast Therapeutics: Employment.

Rapid purification and procoagulant and platelet aggregating activities of Rhombeobin: a thrombin-like/gyroxin-like enzyme from Lachesis muta rhombeata snake venom.

We report a rapid purification method using one-step chromatography of SVSP Rhombeobin (LMR-47) from Lachesis muta rhombeata venom and its procoagulant activities and effects on platelet aggregation. The venom was fractionated by a single chromatographic step in RP-HPLC on a C8 Discovery BIO Wide Pore, showing high degree of molecular homogeneity with molecular mass of 47035.49 Da. Rhombeobin showed amidolytic activity upon BAρNA, with a broad optimum pH (7–10) and was stable in solution up to 60°C. The amidolytic activity was inhibited by serine proteinase inhibitors and reducing agents, but not chelating agents. Rhombeobin showed high coagulant activity on mice plasma and bovine fibrinogen. The deduced amino acid sequence of Rhombeobin showed homology with other SVSPs, especially with LM-TL (L. m. muta) and Gyroxin (C. d. terrificus). Rhombeobin acts, in vitro, as a strong procoagulant enzyme on mice citrated plasma, shortening the APTT and PT tests in adose-dependent manner. The protein showed, “ex vivo”, a strong defibrinogenating effect with 1 µg/animal. Lower doses activated the intrinsic and extrinsic coagulation pathways and impaired the platelet aggregation induced by ADP. Thus, this is the first report of a venom component that produces a venom-induced consumptive coagulopathy (VICC).

Effects of extraction condition on structural features and anticoagulant activity of F. vesca L. conjugates

From the air-dried Wild strawberry (Fragaria vesca L., family Rosaceae) leaves five water-soluble glycoconjugates Fv I–V by different extraction conditions have been isolated. Effects of extraction steps/agents on chemical composition and anticoagulant activity of Fv I–V were examined. Dark brown F. vesca conjugates Fv I–V were recovered in 4.5–8.4% yields, based on dry herb. Isolates were composed of carbohydrate, phenolic and protein components. Fv I–V displayed on HPLC broad molecule-mass distribution patterns with dominance of low molecule-masses 9–14kDa. Their carbohydrate parts revealed high hexuronic acids content (35–60%) while the dominant neutral sugars – galactose, arabinose and rhamnose were found in lower amounts and indicated the presence of rhamnogalacturonans associated with arabinogalactans in all F. vesca preparations. In all Fv I–V isolates high polyphenolic contents were determined, whereas proteins were found in low amounts only. In in vitro experiments on human pooled plasma Fv I–V showed at higher concentrations complete inhibition of plasma clot formation and the most active conjugates in aPTT, PT and TT tests were shown to be Fv I and Fv III, containing the highest amounts of phenolics.

Biological activities of the sulfated polysaccharide from the vascular plant Halodule wrightii

A sulfated polysaccharide (SPSG) was successfully isolated from seagrass Halodule wrightii Asch., Cymodoceaceae, and its antioxidant and anticoagulant activities were investigated. The data presented here showed that the SPSG is a 11 kDa sulfated heterogalactan with a sulfatation degree of 20.63% and it also contains glucose and xylose. SPSG antioxidant activities were evaluated using several in vitro assays and the anticoagulant activity was evaluated by aPTT and PT tests. These assays suggested that the SPSG possessed remarkable antioxidant properties in different in vitro assays and an outstanding anticoagulant activity 2.5-fold higher than that of heparin Clexane® in the aPTT test. This data represents the first reported on the sulfated polysaccharide biological activities from seagrass. These results indicate that SPSG can be considered in the future as a drug utilized in treating diseases from these systems.

Antioxidant and antiproliferative activities of heterofucans from the seaweed Sargassum filipendula.

Fucan is a term used to denominate a type of polysaccharide which contains substantial percentages of l-fucose and sulfate ester groups. We obtained five heterofucans from Sargassum filipendula by proteolytic digestion followed by sequential acetone precipitation. These heterofucans are composed mainly of fucose, glucose, glucuronic acid, galactose and sulfate. These fucans did not show anticoagulant activity in PT and aPTT tests. Their antioxidant activity was evaluated using the follow tests; total antioxidant capacity, scavenging hydroxyl and superoxide radicals, reducing power and ferrous ion [Fe(II)] chelating. All heterofucans displayed considerable activity, especially SF-1.0v which showed the most significant antioxidant potential with 90.7 ascorbic acid equivalents in a total antioxidant capacity test and similar activity when compared with vitamin C in a reducing power assay. The fucan antiproliferative activity was performed with HeLa, PC3 and HepG2 cells using MTT test. In all tested conditions the heterofucans exhibited a dose-dependent effect. The strongest inhibition was observed in HeLa cells, where SF-1.0 and SF-1.5 exhibited considerable activity with an IC50 value of 15.69 and 13.83 μM, respectively. These results clearly indicate the beneficial effect of S. filipendula polysaccharides as antiproliferative and antioxidant. Further purification steps and additional studies on structural features as well as in vivo experiments are needed to test the viability of their use as therapeutic agents.

Polyphenolic-polysaccharide compounds from selected medicinal plants of Asteraceae and Rosaceae families: Chemical characterization and blood anticoagulant activity

The preparations from selected traditional medicinal plants in Poland ( Asteraceae and Rosaceae families), were prepared in the multi-step process of isolation and their anticoagulant activity was measured by APTT and PT tests. The most promising effect was observed for the substances extracted from Fragaria vesca ( Rosaceae) and Echinacea purpurea ( Asteraceae). They showed interesting activity with respect to the activity of 5th International Standard for Unfractionated Heparin in APTT method. The structure characterization by IR, HPLC, GLC-MS and colorimetric methods revealed that these preparations are macromolecular polysaccharide–polyphenolic conjugates, similar to cell wall acidic macromolecular fragments which are common in the higher plants. The high content of hexuronic acids, as well as phenolic glycoconjugates seems to be responsible for the observed anticoagulant activity.

Protein C, protein S and other pro- and anticoagulant activities among epileptic children using sodium valproate

This study was conducted to evaluate some anticoagulants’ (protein C, protein S and antithrombin) activities among epileptic children treated with VPA and to learn if thromboembolic events occur among these children or their parents. Twenty-five boys and 15 girls using VPA for at least 3 months were included in the VPA group. The control group consisted of 28 boys and 12 girls who had no infection and did not use any medication that could alter protein C activity. Complete blood counts, ALT, AST, PT, aPTT, fibrinogen, protein C, protein S and AT tests were studied in both groups. Serum VPA levels were determined in the VPA group. Protein C and protein S activities of the children in the VPA group were significantly lower than those in the control group (89.5 ± 19.3% vs 104.9 ± 21.7% and 44.6 ± 16.3% vs 59.4 ± 28.4%, respectively). Neither children using VPA, nor their parents had any thromboembolic events in medical history. Platelet counts, ALT and fibrinogen levels in the VPA group were significantly lower than those in the controls. A negative correlation was found between serum VPA level and platelet counts. There were also negative correlations between fibrinogen and serum VPA levels, and between fibrinogen level and protein S activity. The children in the VPA group had lower PT and higher aPTT levels than the children in the control group. Since other factors known to alter the anticoagulant activities and liver functions were eliminated initially, the decreases of protein C and protein S activities, thrombocyte counts, ALT, PT and fibrinogen levels and increase in aPTT level may be attributed to VPA. VPA hepatotoxicity can be the cause of decreased pro- and anticoagulant activities.

The need for routine pre-operative coagulation screening tests (prothrombin time PT/partial thromboplastin time PTT) for healthy children undergoing elective tonsillectomy and/or adenoidectomy

In some medical centers, the routine pre-operative evaluation of healthy children undergoing elective tonsillectomy and/or adenoidectomy (T and A) includes coagulation screening tests (PT, prothrombin Time; PTT, partial thromboplastin time; and INR, international normalized ratio). In this retrospective study, we determined whether there is a positive correlation between prolonged PT/PTT/INR tests in healthy children, with no prior medical history of coagulation problems, and bleeding during surgery and/or bleeding in the month following surgery. We reviewed the records of 416 elective T and A surgeries performed at the Soroka University Medical Center in Beer-Sheva, Israel, over the course of 1999. One hundred and twenty-one (29.1%) patients had preoperative prolonged PT values but only four (3.3%) of these patients experienced light bleeding during surgery. Seven (5.8%) of the 121 patients with prolonged PT tests experienced bleeding episodes during the 1st month subsequent to the surgery. Of the 65 (15.6%) patients who had prolonged pre-operative INR values, only three (4.6%) experienced light bleeding during surgery. Two (3.1%) patients with prolonged INR values experienced light bleeding during the 1st month subsequent to surgery. Sixty-one (14.7%) patients had prolonged first preoperative PTT values, only five of whom (8.2%) experienced light bleeding during surgery. Two (3.3%) of the 61 with prolonged PTT values experienced light bleeding during the 1st month subsequent to surgery. We therefore concluded that pre-operative coagulation screening tests provide low sensitivity and low bleeding predictive value. As such, routine coagulation tests before T &A are not indicated unless a medical history of bleeding tendency is suspected.

Similar Mechanism of Various Lupus Anticoagulants

Potent lupus inhibitors from various patients were mixed with platelet free normal plasma and were compared in activated partial thromboplastin time (APTT), dilute prothrombin time (dil. PT), kaolin clotting time (KCT), contact product clotting time (CPCT), and Russell viper venom clotting time (RVVCT) tests. In the last three tests platelets and platelet lipid substitutes were avoided to enhance the sensitivities of these tests for the lupus anticoagulant. Correlations between the KCT and the other tests were mostly good, indicating that different lupus inhibitors functioned by a similar mechanism. There was no significant trend between particular clinical symptoms and individual coagulation test combinations. The KCT was found to be the most sensitive test for the lupus inhibitor, followed by the CPCT, RVVCT, dil. PT and APTT tests. Activated platelets tended to correct the APTT lupus inhibitor defect in all except the strongest inhibitor cases.

The Effects of Hepes Buffer on Clotting Tests, Assay of Factors V and VIII and on the Hydrolysis of Esters by Thrombin and Thrombokinase

Shorter clotting times were found in the presence of 50 mM Hepes (N-2-hydroxyethylpiperazine-N1-2-ethanesulfonic acid) buffer than of 50mM Imidazole buffer in one-stage assays of factors V and VIII, in modified APTT and PT tests and in tests of the clotting of human plasma by purified human thrombin. All tests were performed at ionic strength 0.155 in the presence of either Hepes. NaOH or Imidazole. HCl buffer, pH 7.4 at 37 degrees. The faster clotting in the presence of Hepes buffer, therefore, is probably due, at least in part, to acceleration by Hepes of thrombin's enzymatic action on fibrinogen and/or of the polymerization of the fibrin monomers. Hepes may also have effects of other blood clotting reactions. Rates of hydrolysis of TAME or BAME (p-toluenesulfonyl- or benzoyl-L-arginine methyl ester) at pH 7.4 37 degrees by purified human bovine thrombin were essentially the same in 200 mM Hepes as in 250 mM Tris. HCl buffer (rates in Hepes. NaOH or Hepes. KOH buffers were compared with those in Tris. HCl plus NaCl for KCl). However, with purified bovine thrombokinase, rates of TAME hydrolysis in Hepes buffer were accelerated and rates of BAME hydrolysis slightly inhibited. Hepes, therefore, reacts with thrombokinase but whether this accelerates (or inhibits) the rate of converting prothrombin to thrombin remains to be determined. In addition, Hepes has an inhibitory effect on clotting since increasing the concentration of Hepes from 50 mM to 200 mM inhibits clotting in the PT, APTT and bovine thrombin-human plasma tests. Hepes buffer is being added to some plasmas and to some reagents used in clotting tests. It is, therefore, important to realize that its concentration must be monitored closely or erroneous results may be obtained in clotting tests and assays of clotting factors. The clotting times were the same in the presence of 50 mM Tris. HCl as in Imidazole. HCl buffers in APTT tests at three ionic strengths but they differed slightly in plasma-thrombin tests. Depending upon the ionic strength, 17 mM Barbital Sodium. HCl buffer inhibited APTT tests but accelerated plasma-thrombin tests. All the buffers tested, therefore, have individual effects on the clotting tests.