Opartkiattikul N

Activation of the coagulation cascade in patients with leptospirosis.

BACKGROUND Disseminated intravascular coagulation (DIC) is common among patients with sepsis. Leptospirosis is an important cause of sepsis in tropical areas, and pulmonary hemorrhage associated with thrombocytopenia is the major cause of death, but the coagulopathy in severe leptospirosis has not been further characterized. The aim of this study was to evaluate coagulation factors and the presence of DIC in patients with leptospirosis in northeast Thailand. METHODS We measured plasma concentrations of fibrinogen, D-dimer, thrombin-antithrombin III complexes, and prothrombin fragment 1,2 and evaluated the DIC score in 79 patients with culture-confirmed and/or serologically confirmed leptospirosis and in 33 healthy Thai control subjects. RESULTS The median concentrations of fibrinogen, D-dimer, thrombin-antithrombin III complexes, and prothrombin fragment 1,2 were significantly elevated in a cohort of 79 patients with leptospirosis, compared with healthy control subjects (P<or=.001 for all tests). Patients with leptospirosis had significantly longer prothrombin times, longer activated partial thromboplastin times, and lower platelet counts. Thrombocytopenia was present in 38% of case patients and occurred more frequently among patients with culture-negative leptospirosis; in multivariate analysis, it was the only hemostasis factor independently associated with clinical bleeding. Patients who were culture-negative for Leptospira species had higher Acute Physiology and Chronic Health Evaluation II and Sepsis-Related Organ Failure Assessment scores and more bleeding complications. Nearly one-half of patients with leptospirosis had overt DIC as defined by an International Society on Thrombosis and Hemostasis DIC score. CONCLUSIONS Activation of the coagulation system is an important feature of leptospirosis. Thrombocytopenia is an indicator of severe disease and risk of bleeding.

Guava leaf extract and topical haemostasis.

The effects of guava leaf extract on the bleeding time and the three main mechanisms of haemostasis: vasoconstriction, platelet aggregation and blood coagulation, were investigated. The water extract of guava leaves did not shorten bleeding times in rats. Guava leaf extract potentiated the vascular muscle contraction induced in rabbits by phenylephrine, and when given alone it stimulated human platelet aggregation in vitro in a dose‐dependent manner. On the other hand, it significantly prolonged blood coagulation; activated partial thromboplastin time (APTT) test (p < 0.05). The higher the concentration of the extract, the longer APTT was observed. Thus, a water extract of guava leaves showed ambiguous effects on the haemostatic system. Guava leaf extract did not affect bleeding times, it stimulated vasoconstriction and platelet aggregation but it inhibited blood coagulation. Therefore, guava leaf extract is not recommended as a haemostatic agent. Copyright

Detection of haemoglobin variants and inference of their functional properties using complete oxygen dissociation curve measurements

Complete oxygen dissociation curves for red cell suspensions of three haemoglobinopathies, namely haemoglobin (Hb) H, Hb Köln and Hb Tak/β thalassaemia diseases, were measured using automatic recording methods. These curves were left‐shifted compared with the normal red cell curve and showed a biphasic shape as a result of co‐existence of the high and normal affinity haemoglobin components. Computer‐assisted simulation of these biphasic curves enabled us to infer the curves for the pure abnormal haemoglobins and their fraction in the total haemoglobin of the red cell. The inferred values of fraction agreed with those determined by haemoglobin type analysis or the literature values. The curve for Hb Köln red cells deviated from the normal red cell curve in the whole range of oxygen saturation, whereas the curve for Hb H was close to the normal curve at the middle and upper portions. This difference in deviation was ascribed to a possible interaction between Hb Köln and Hb A through subunit exchange, and its absence between Hb H and Hb A. The present results indicate that measurement of the complete oxygen dissociation curve is important for the detection of non‐interacting variants such as Hb H and is useful for inferring the functional properties of haemoglobin components that are not easily isolated.

Detection of PF3 availability in whole blood from volunteers and beta-thalassemia/HbE patients: a promising method for prediction of thrombotic tendency.

The platelet factor 3 (PF 3) plays a very important role in activation of coagulation factors and is regarded to be available during activation of platelets. However, membrane fraction of erythrocytes is also shown to have PF 3-like activity, suggesting that the abnormal erythrocytes may accelerate the activation of platelet by forming thrombin on their abnormal membrane or by way of other factors of the abnormal erythrocytes, and may increase the availability of PF 3 in whole blood (WB). To examine this hypothesis, we developed a method for determination of PF 3 activity, because the method now available for the PF3 determination could not detect changes in PF 3 activity with time. The principles of our method were as follows: 1) The reaction system was adjusted so that the amount of thrombin generated in a fixed reaction time correlates with the amount of PF 3. 2) To avoid inhibition of thrombin activity by antithrombin III, a synthetic thrombin inhibitor, MD 805, was added to the system and the activity of thrombin generated was measured by synthetic thrombin substrate S-2238 using A405 as an indicator of the availability of PF3. The results obtained by the method were the following: WB taken from volunteers showed A405 of 0.12 +/- 0.02 at 30 minutes after blood collection and then the A405 increased to 0.27 +/- 0.03 at 90 minutes. However, one volunteer showed the value of 0.59 at 90 minutes, though the value at 30 minutes was 0.16. The platelet number in his WB did not change during the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Improvement of Coagulation Laboratory Practice in Thailand: The First-Year Experience of the National External Quality Assessment Scheme for Blood Coagulation

CONTEXT In Thailand until 2005 there had been no external quality assessment scheme at the national level for blood coagulation tests. Only a few laboratories had an external quality assessment for these tests. In the year 2005, the Thailand National External Quality Assessment Scheme for Blood Coagulation was founded. OBJECTIVES To describe the establishment of the Thailand National External Quality Assessment Scheme for Blood Coagulation (including problems encountered and solutions), its progression and expansion, and the improvement of coagulation laboratory practice in Thailand during 2 trial surveys and 4 formal surveys conducted in the first 1 1/2 years. DESIGN Between 2005 and 2006, the external quality assessment samples for prothrombin time/international normalized ratio and activated partial thromboplastin time were distributed to the participants as well as the instructions and suggestions for the improvement of laboratory practice. From the data collected, the all-method coefficient of variation of the international normalized ratio and activated partial thromboplastin time was calculated for each survey. RESULTS The number of participants increased during the first 1 1/2 years that the surveys were conducted, from 109 to 127. Survey data demonstrate an improvement in response rate and an increase in the number of laboratories that determine their own reference ranges and repeat this for every change of reagent lot, using the appropriate anticoagulant. The increased precision of tests is indicated by the decrease of the all-method coefficient of variation of the international normalized ratio and activated partial thromboplastin time. Examples of individual laboratory improvement through feedback are also described. CONCLUSIONS The improvement of coagulation laboratory practice both through the instructions provided and liaison with participants was observed during the course of this scheme.

Point-of-care glucose testing: on-site competency assessment

PURPOSE The purpose of this pilot paper is to use on-site assessment to determine common non-compliance in point-of-care (POC) glucose testing, deficiencies that should be improved by the POC team or emphasized in further training. DESIGN/METHODOLOGY/APPROACH Assessment forms for POC site and staff competency were developed and used for direct observation in four POC sites. Nurses were sampled in these sites. FINDINGS The on-site assessment demonstrated that initial operator training was insufficient. Only three of 15 nurses achieved a satisfactory score on the first assessment. In all nine participants who had been assessed at least twice improved their performance. In total, 16 (30 percent) of 53 competency items were not achieved, so these should be addressed during refresher training. Improved compliance with the checklist was observed in two of four POC sites. RESEARCH LIMITATIONS/IMPLICATIONS Medical students and residents also perform the test, so more representative samples are needed. PRACTICAL IMPLICATIONS The assessment of staff performance in the workplace with constructive input and POC site inspections to identify common deficiencies are recommended. Refresher trainings should be focussed on the deficiencies identified. SOCIAL IMPLICATIONS Assessing staff performance in the workplace with constructive input and POC site inspections to identify common deficiencies are recommended. Refresher trainings should focus on deficiencies. ORIGINALITY/VALUE This study involved directly observing POC site staff during glucose testing. The assessment forms were based on ISO 22870:2006 technical requirements.

An evaluation of prothrombin assay method using MD805 by means of warfarin-treated plasma

The prothrombin assay method using the synthetic thrombin-inhibitor MD805 was standardized by fixing the concentrations of MD805 and S-2238 through their extinction coefficients (epsilon 333 for MD805 and epsilon 316 for S-2238). The prothrombin assay was directly proportional to the concentration of plasma up to 200% of the normal level and was not significantly influenced by the variety of three kinds of commercially available tissue thromboplastin preparations. Using plasma from Warfarin-treated patients and healthy volunteers, the correlation was studied between the prothrombin assay and the conventional coagulation tests such as Prothrombin time (INR), Thrombotest and Hepaplastintest (Normotest), and the correlation coefficients of -0.85, 0.81 and 0.94 were obtained respectively. FUT-175 and MD805 in the test plasma hardly affected the prothrombin assay in the concentration ranges which affected remarkably the conventional coagulation tests. These results indicated that the prothrombin assay was useful for monitoring the hyper- or hypoprothrombin state even on anticoagulant therapy. Eighteen healthy volunteers at 18 to 20 years old showed the mean and standard deviation of 0.96 +/- 0.097.