Validation of high concentrated thrombin time assay for unfractionated heparin monitoring.

BACKGROUND: The high concentrated thrombin time (hcTT), a thrombin time modified by increasing the thrombin concentration, is a possible alternative assay to activated partial thromboplastin time (aPTT) in unfractionated heparin (UFH) monitoring. This study aimed to determine the optimal thrombin concentration used in the hcTT assay for UFH monitoring. METHODS: A total of 30 blood samples obtained from healthy volunteers were included in this study. Thrombin concentrations of 10.0, 15.0, 20.0, and 25.0 IU/ml were used in the hcTT assay. The consistency between the hcTT and anti-FXa assays was evaluated. To validate the hcTT assay, linearity, repeatability, reproducibility, and diagnostic performance of the assay were assessed. RESULTS: The hcTT assay using thrombin concentration of 15.0 IU/ml showed a strong correlation to the anti-FXa assay with R2 of 0.72 and the Spearman's correlation coefficient (rs ) of 0.97 (95% CI, 0.96-0.98). Within-run and day-to-day run variabilities of the assay were satisfactory (all coefficients of variation <10%). We found an excellent correlation between the results which were measured using different reagents with intra- or inter-laboratory instruments. Notably, as compared to the aPTT assay, the hcTT assay showed a significantly better performance in identifying the samples which contain UFH at the supratherapeutic level, with an AUC of 0.97 vs. 0.91, p = 0.049. CONCLUSION: The hcTT assay can be used as an alternative assay for UFH therapy monitoring. A further study using clinical samples is recommended to confirm the appropriateness of the hcTT assay for clinical application.

The hypoferremic response to acute inflammation is maintained in thalassemia mice even under parenteral iron loading.

BACKGROUND: Hepcidin controls iron homeostasis by inducing the degradation of the iron efflux protein, ferroportin (FPN1), and subsequently reducing serum iron levels. Hepcidin expression is influenced by multiple factors, including iron stores, ineffective erythropoiesis, and inflammation. However, the interactions between these factors under thalassemic condition remain unclear. This study aimed to determine the hypoferremic and transcriptional responses of iron homeostasis to acute inflammatory induction by lipopolysaccharide (LPS) in thalassemic (Hbbth3 /+) mice with/without parenteral iron loading with iron dextran. METHODS: Wild type and Hbbth3 /+ mice were intramuscularly injected with 5 mg of iron dextran once daily for two consecutive days. After a 2-week equilibration, acute inflammation was induced by an intraperitoneal injection of a single dose of 1 µg/g body weight of LPS. Control groups for both iron loading and acute inflammation received equal volume(s) of saline solution. Blood and tissue samples were collected at 6 hours after LPS (or saline) injection. Iron parameters and mRNA expression of hepcidin as well as genes involved in iron transport and metabolism in wild type and Hbbth3 /+ mice were analyzed and compared by Kruskal-Wallis test with pairwise Mann-Whitney U test. RESULTS: We found the inductive effects of LPS on liver IL-6 mRNA expression to be more pronounced under parenteral iron loading. Upon LPS administration, splenic erythroferrone (ERFE) mRNA levels were reduced only in iron-treated mice, whereas, liver bone morphogenetic protein 6 (BMP6) mRNA levels were decreased under both control and parenteral iron loading conditions. Despite the altered expression of the aforementioned hepcidin regulators, the stimulatory effect of LPS on hepcidin mRNA expression was blunt in iron-treated Hbbth3 /+ mice. Contrary to the blunted hepcidin response, LPS treatment suppressed FPN1 mRNA expression in the liver, spleen, and duodenum, as well as reduced serum iron levels of Hbbth3 /+ mice with parenteral iron loading. CONCLUSION: Our study suggests that a hypoferremic response to LPS-induced acute inflammation is maintained in thalassemic mice with parenteral iron loading in a hepcidin-independent manner.

Iron homeostasis in a mouse model of thalassemia intermedia is altered between adolescence and adulthood.

BACKGROUND: Iron overload is one of common complications of ß-thalassemia. Systemic iron homeostasis is regulated by iron-regulatory hormone, hepcidin, which inhibits intestinal iron absorption and iron recycling by reticuloendothelial system. In addition, body iron status and requirement can be altered with age. In adolescence, iron requirement is increased due to blood volume expansion and growth spurt. Heterozygous ß-globin knockout mice (Hbbth3 /+; BKO) is a mouse model of thalassemia widely used to study iron homeostasis under this pathological condition. However, effects of age on iron homeostasis, particularly the expression of genes involved in hemoglobin metabolism as well as erythroid regulators in the spleen, during adolescence have not been explored in this mouse model. METHODS: Iron parameters as well as the mRNA expression of hepcidin and genes involved in iron transport and metabolism in wildtype (WT) and BKO mice during adolescence (6-7 weeks old) and adulthood (16-20 weeks old) were analyzed and compared by 2-way ANOVA. RESULTS: The transition of adolescence to adulthood was associated with reductions in duodenal iron transporter mRNA expression and serum iron levels of both WT and BKO mice. Erythrocyte parameters in BKO mice remained abnormal in both age groups despite persistent induction of genes involved in hemoglobin metabolism in the spleen and progressively increased extramedullary erythropiesis. In BKO mice, adulthood was associated with increased liver hepcidin and ferroportin mRNA expression along with splenic erythroferrone mRNA suppression compared to adolescence. CONCLUSION: Our results demonstrate that iron homeostasis in a mouse model of thalassemia intermedia is altered between adolescence and adulthood. The present study underscores the importance of the age of thalassemic mice in the study of molecular or pathophysiological changes under thalassemic condition.

Prevalence of Thalassemia and Glucose-6-Phosphate Dehydrogenase Deficiency in Newborns and Adults at the Ramathibodi Hospital, Bangkok, Thailand.

Thalassemias and glucose-6-phosphate dehydrogenase (G6PD) deficiency are the most common inherited blood disorders. They are distributed among populations living in malaria endemic regions resulting in survival advantage from severe malaria disease. The aims of this study were to analyze the prevalence of thalassemias and G6PD deficiency at the Ramathibodi Hospital, Bangkok, Thailand. A total of 616 adult and 174 cord blood samples were collected and analyzed for red blood cell (RBC) parameters, hemoglobin (Hb) typing and DNA analysis for G6PD mutations and α-thalassemia (α-thal). The two most prominent types of thalassemia were heterozygous Hb E (HBB: c.79G>A), (19.5% in newborns and 35.6% in adults) followed by heterozygous α-thal-2 [-α3.7 (rightward) deletion] at 18.7% in newborns and 19.5% in adults. After performing G6PD genotyping using multiplex amplification refractory mutation system-polymerase chain reaction (multiplex ARMS-PCR) for 10 G6PD mutations, the prevalence of G6PD mutation was found in 12.0% of newborns and 11.7% of adults. The G6PD Viangchan [871 (G>A)] is the most common G6PD mutation in newborns (42.9%) and adults (52.8%). In addition, coinheritance of various types of thalassemia with G6PD deficiency were found. The results indicated that heterozygous Hb E and G6PD Viangchan are predominant both in newborns and adults in this study.

Molecular Epidemiology of Hemoglobinopathies in Cambodia.

Determining the magnitude of the thalassemia problem in a country is important for implementing a national prevention and control program. In order to acquire accurate thalassemia prevalence data, the gene frequency of α- and ß-thalassemia (α- and ß-thal) in different regions of a country should be determined. The molecular basis of thalassemia in Cambodia was performed by polymerase chain reaction (PCR)-based techniques in a community-based cross-sectional survey of 1631 unrelated individuals from three regions, Battambang, Preah Vihear and Phnom Penh. Thalassemia mutations were detected in 62.7% of the three studied population of Cambodia. Hb E (HBB: c.79G > A) was the most common ß-globin gene mutation with a frequency ranging from 0.139 to 0.331, while the most frequent α-globin gene mutation was the -α(3.7) (rightward) deletion (0.098-0.255). The other frequencies were 0.001-0.003 for ß-thal, 0.008-0.011 for α-thal-1 (- -(SEA)), 0.003-0.008 for α-thal-2 [-α(4.2) (leftward deletion)], 0.021-0.044 for Hb Constant Spring (Hb CS, HBA2: c.427T > C) and 0.009-0.036 for Hb Paksé (HBA2: c.429A > T). A regional specific thalassemia gene frequency was observed. Preah Vihear had the highest prevalence of Hb E (55.9%), α-thal-2 (24.0%) and nondeletional α-thal (15.1%), whereas Phnom Penh had the lowest frequency of thalassemia genes. Interestingly, in Preah Vihear, the frequency of Hb Paksé was extremely high (0.036), almost equivalent to that of Hb CS (0.044). Our results indicate the importance of micromapping and epidemiology studies of thalassemia, which will assist in establishing the national prevention and control program in Cambodia.

Identification of Hb Constant Spring (HBA2: c.427T > C) by an Automated High Performance Liquid Chromatography Method.

Laboratory investigation of hemoglobinopathies includes complete blood count (CBC), hemoglobin (Hb) typing by high performance liquid chromatography (HPLC) and DNA analysis. DNA analysis is the most reliable method but requires a manually laborious procedure and is time consuming. A more practical method of detecting abnormal Hbs is the HPLC technique, because it is more rapid and easier to interpret. Hb Constant Spring (Hb CS; HBA2: c.427T > C) is an abnormal variant that is labile and difficult to detect using conventional methods. To evaluate the efficiency of Hb CS determination by HPLC, blood samples from 578 subjects were analyzed using an automated cell analyzer for hematological parameters, automated HPLC for Hb identification, and polymerase chain reaction (PCR) for α-thalassemia (α-thal) and Hb CS confirmation. These included 169 normal, 119 heterozygous α-thal-2, 30 homozygous α-thal-2, 177 heterozygous α-thal-1, 59 heterozygous Hb CS, seven homozygous Hb CS and 17 compound heterozygous α-thal-2 and Hb CS subjects. The results showed that sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Hb CS by HPLC were 93.78, 99.80, 98.73 and 99.00%, respectively. The mean of misdiagnosis value of the three groups of Hb CS subjects (total 83) was 6.02% (n = 5), with percentages for heterozygous Hb CS, homozygous Hb CS, and compound heterozygous α-thal-2 and Hb CS being 6.8, 0.0 and 5.9%, respectively. The HPLC method yielded good results, although it may also lead to misdiagnosis of Hb CS due to the relatively small amount and lability.

Vascular leakage in dengue hemorrhagic Fever is associated with dengue infected monocytes, monocyte activation/exhaustion, and cytokines production.

The vascular leakage was shown by the increment of hematocrit (Hct), dengue viral infected monocyte, monocyte status, and cytokines production in patients infected with dengue virus. Dengue viral antigens were demonstrated in monocytes (CD14+) from peripheral blood mononuclear cells. The increased levels of Hct, interleukin- (IL-) 10, and tumor necrosis factor-alpha (TNF-α) were detected in dengue fever (DF), dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) patients as compared with other febrile illnesses (OFIs). The highest levels of Hct and IL-10 were detected in DSS patients as compared with other groups (P < 0.05) especially on one day before and after defervescence. The unstimulated and lipopolysaccharide- (LPS-) stimulated monocytes from DSS patients showed the significantly decreased of intracellular IL-1ß and TNF-α. In addition, the lowest level of mean fluorescence intensity (MFI) of CD11b expression on monocytes surface in DSS patients was also demonstrated. Furthermore, the negative correlations between IL-10 levels and intracellular IL-1ß and MFI of CD11b expression in unstimulated and LPS-stimulated monocytes were also detected. Nevertheless, not only were the relationships between the prominent IL-10 and the suppression of intracellular monocyte secretion, namely, IL-1ß, TNF-α, demonstrated but also the effect of vascular leakage was observed.

Elevated erythropoietin and cytokines levels are related to impaired reticulocyte maturation in thalassemic patients.

Serum EPO concentration is related primarily to the rate of erythrocyte production and, under the stimulation of hypoxia, increases exponentially as hemoglobin (Hb) decreased. The level of EPO was determined in 141 subjects including 43 normal, 44 thalassemic patients and 54 thalassemic trait subjects. The EPO level was significantly higher in the thalassemic patients (54.8mU/ml in HbH disease [α thal1/α thal2;], 78.1mU/ml in HbH with Hb CS [α thal 1/CS]; 95.6mU/ml in ß-thal/HbE splenectomized [BE(S)]; and 114.8mU/ml in ß-thal/HbE non-splenectomized [BE(NS)]as compared with 12.0mU/ml in normal subjects. No significant differences were detected in thalassemic trait subjects. In addition, the levels of EPO in thalassemic patients is correlated significantly with the number of reticulocytes and the reticulocyte fractions especially the fraction of immature reticulocytes. Interestingly, the highest level of EPO/% retic ratio as indicated for EPO non-responder was detected in BE(NS) patients. However, the impaired reticulocytes maturation was found to be related significantly with the levels of TNF-α,IFN-γ,IL-10, and VEGF. Since, TNF-α, IFN-γ, IL-10 and VEGF are reported as the cytokines with erythropoietic inhibitory mediators, the variation of these cytokines in thalassemic environments may be associated to the anemic crisis in these patients.

Comparison of a simple-probe real-time PCR and multiplex PCR techniques for HPA-1 to HPA-6 and HPA-15 genotyping.

BACKGROUND: We aimed to compare HPA-1 to HPA-6 and HPA-15 genotyping results obtained by a simple-probe real-time polymerase chain reaction (PCR) technique with the multiplex PCR technique. METHODS: Five hundred DNA samples from the Thai National Stem Cell Donor Registry (TSCDR) of the National Blood Centre, Thai Red Cross Society were included. Human platelet antigen (HPA) genotyping was performed by simple-probe real-time PCR and multiplex PCR techniques. RESULTS: HPA-1, HPA-2, HPA-3, and HPA-4 genotyping results obtained by both techniques were in agreement. The misinterpretation of HPA-5, HPA-6, and HPA-15 genotypes was found in eight samples by simple-probe real-time PCR and HPA genotypes were confirmed by DNA sequencing. Two samples of HPA-5 were misinterpreted as HPA-5a5a instead of HPA-5a5b due to an NM_002203.3:c.1594A>C mutation (rs199808499) near the HPA-5 polymorphism (5' side). Five samples of HPA-6a6b were misinterpreted as HPA-6b6b because of an NM_000212.2:c.1545G>A mutation (rs4634) adjacent to the HPA-6 polymorphism (3' side). Interestingly, one sample of HPA-15a15b was misinterpreted as HPA-15b15b due to an NM_133493.1:c.2118C>A mutation near the HPA-15 polymorphism (3' side). CONCLUSIONS: HPA genotyping results by two PCR techniques were compared. Incorrect assignments were found due to genetic variations near each HPA single nucleotide polymorphism. Therefore, to avoid false assignation, the use of two genotyping techniques is recommended.

Cardiomyocyte ultrastructural damage in ß-thalassaemic mice.

ß-thalassaemia is a hereditary anaemia resulting from the absence or reduction in ß-globin chain production. Heart complications related to iron overload are the most serious cause of death in these patients. In this report cardiac pathology of ß-thalassaemic mice was evaluated by light and electron microscopy. The study was carried out in thalassaemic mice carrying human ß-thalassaemia mutation, IVSII-654 (654), transgenic mice carrying human ß(E) -globin transgene insertion (E4), thalassaemic mice with human ß(E) -globin transgene insertion (654/E4) and homozygous thalassaemic mice rescued by the human ß(E) -globin transgene (R), which is generated by cross-breeding between the 654 and E4 mice. Histology showed iron deposition in cardiac myocytes of 654 and R mice, but the ultrastructural damage was observed only in the R mice when compared with the wild type, 654, E4 and 654/E4 mice. Histopathological changes in the cardiomyocytes of the R mice included mitochondrial swelling, loss of myofilaments and the presence of lipofuscin, related to the increased level of tissue iron content. The progressive ultrastructural pathology in R mice cardiomyocytes is consistent with the ultrastructural pathology previously studied in patients with thalassaemia. Thus, this R thalassaemic mouse model is suitable for in vivo pathophysiological study of thalassaemic heart.

Tumour necrosis factor gene polymorphism in dengue infection: association with risk of bleeding.

BACKGROUND: A single nucleotide polymorphism located at the promoter -308A of tumour necrosis factor-alpha (TNF-α) gene may affect transcription and increase cytokine production, leading to the severe manifestation of dengue virus infection. AIM: To study the association of the TNF-α -308A allele and the severity of patients with dengue infection. METHODS: 112 patients suspected of having dengue infection and 106 normal controls were enrolled in the study. Mean (SD) age was 10.4 (3.6) years. In all, 19 and 82 patients were diagnosed with dengue fever (DF) and dengue haemorrhagic fever (DHF), respectively, while 11 were diagnosed with other febrile illnesses (OFIs). They were tested for the polymorphisms at the promoter -308 position of the TNF-α gene and their TNF-α levels were measured. RESULTS: In the patients with dengue infection (14/202, 6.9%) with OFIs (1/22, 4.5%) and in normal controls (17/212, 8.0%), the frequency of the TNF-α -308A allele was not significantly different. Moreover, no statistically significant difference was found in patients with various clinical manifestations of dengue infection involving DF (5.3%, 2/38), DHF grade I (5.0%, 2/40), DHF grade II (9.5%, 4/42), DHF grade III (2.5%, 1/40) and DHF grade IV (11.9%, 5/42). However, patients with dengue infection and significant bleeding manifestations, apart from petechiae and ecchymosis, tended to have a higher frequency of the TNF-α -308A allele (11.8%, 9/76) than those without significant bleeding manifestations (5/126, 4.0%) (P = 0.056). The levels of TNF-α were additionally measured in 67 patients but the results failed to demonstrate a functional effect in the transcriptional rate of the TNF-α -308A allele. CONCLUSION: In patients with dengue infection there is an association between the TNF-α -308A allele and the risk of bleeding. The test may be used as one of the predictors of the severity of dengue infection.

Alteration of cytokines and chemokines during febrile episodes associated with endothelial cell damage and plasma leakage in dengue hemorrhagic fever.

BACKGROUND: The leakage of plasma during febrile episodes in dengue-infected patients is a severe condition leading to dengue shock syndrome. Alteration of cytokines/chemokines is suspected to be a major cause of endothelial cell damage in these patients. The study was designed to demonstrate the alteration of cytokines and chemokines in dengue-infected patients during febrile episodes. METHODS: The blood samples from 164 patients with dengue fever, dengue hemorrhagic fever and other febrile illnesses were collected daily from the day of hospitalization until discharge and also in the convalescent stage. The levels of cytokines/chemokines were determined using a sandwich chemiluminescent immunoassay, and the hematological parameters were examined by the ADVIA hematological analyzer. RESULTS: Two patterns of cytokines/chemokines alteration were detected at different time points during the febrile episode. The increased factors included interleukin (IL)-4, IL-6, IL-8, IL-10, tumor necrosis factor-α, interferon-γ and monocyte chemoattractant protein-1 whereas IL-1ß, IL-2, vascular endothelial growth factor and epidermal growth factor were decreased. Several cytokines were correlated with disease severity especially in dengue hemorrhagic fever/dengue shock syndrome patients. CONCLUSIONS: The alteration in the cytokine/chemokine kinetics during a febrile episode can be used as a predictor for severe dengue infection. The increased and decreased levels at different time points can indicate the disease progression related to vascular leakage in dengue hemorrhagic fever/dengue shock syndrome patients.

A rare Hb H disease due to the - -(SEA) and 16.6 kb α-thalassemia-2 deletions.

A large deletional α-thalassemia-2 (α-thal-2) allele was identified in a Thai woman with Hb H disease. The proband has α-thal-1 (SEA type) in conjunction with a 16.6 kb deletion affecting the α2-globin allele. The proband had severe anemia and required a blood transfusion during puerperium.

Nondeletional Hb Queens Park [α32(B13)Met→Lys]/Hb H (ß4) disease.

A rare nondeletional α-thalassemia-2 (α-thal-2) allele was identified in a Thai boy with Hb H (ß4) disease. The proband has α-thal-1 (- -(SEA) type) together with a non productive Hb Queens Park (HBA1:c.98T>A) [α32(B13)Met→Lys] α1-globin variant. No abnormal hemoglobin (Hb) fraction was detected by high performance liquid chromatography (HPLC). The clinical effect of this mutation in the proband was comparable to that of deletional α-thal-2 present in Hb H disease.

Clinical practice guidelines for children with cancer presenting with fever to the emergency room.

BACKGROUND: Patients with febrile neutropenia (FN) may develop severe infection, septic shock, and death. To improve the outcome of pediatric oncology patients with suspected FN, clinical practice guidelines were developed for these patients at the emergency room (ER). The objective of the present study was to evaluate compliance of the clinical practice guidelines for children with cancer presenting with fever to the ER and adverse outcomes after using the guidelines. METHODS: A retrospective cohort study was undertaken of children with cancer presenting with fever to the ER from January 2007 to December 2008 after the clinical guidelines were implemented. The control group was the children with cancer who presented with fever during January 2005-December 2006. Guideline compliance was evaluated by recording the time of initial clinical and laboratory assessment and door-to-antibiotic time. The adverse outcomes, including septic shock and death, were determined. RESULTS: There were 170 febrile episodes after using the guidelines. Approximately half (49.4%) of the patients received clinical assessment and laboratory results within 60 min, whereas the antibiotics were administered within 120 min in 80%. Prevalence of septic shock and intensive care unit admission were significantly reduced compared to controls (P = 0.011 and 0.016, respectively). No infection-associated mortality was found after the implementation of the guidelines. CONCLUSIONS: Using the clinical practice guidelines for pediatric oncology patients with fever was found to reduce the adverse outcomes and improve survival.

Quantitative analysis of Hb Bart's in cord blood by capillary electrophoresis system.

It has long been recognized that the presence of hemoglobin (Hb) Bart's in newborn's blood is associated with α-thalassemia. However, the automated high-performance liquid chromatography or low-performance liquid chromatography system is unable to quantify the amount of Hbs Bart's and H, which are eluted at the retention time close to 0 min. This study used automatic capillary electrophoresis (CE) system to diagnose various types of α-thalassemia in 587 cord blood samples, including 429 normal α-globin genotype, 120 cases of thalassemia with one α-globin gene defect, 34 cases with two α-globin genes defect, and four cases with three α-globin genes defect. The result showed that the level of Hb Bart's in cord blood was increased accordingly with the increasing numbers of the defective α-globin genes. In addition, Hb Bart's level at 0.2%, as measured by CE, can be used as a cut-off point for α-thalassemia diagnosis in newborns.

Activation of mononuclear phagocytes and its relationship to asplenia and phosphatidylserine exposing red blood cells in hemoglobin E/ß-thalassemia patients.

Aged or abnormal red blood cells with exposed phosphatidylserine (PSRBCs) are cleared from the circulation by splenic macrophages. In asplenic patients, other mononuclear phagocytic cells in tissues and in circulation may function in this capacity. To better understand these changes and the relationship among splenic status, PS-RBCs, blood monocytes, and serum tumor necrosis factor (TNF-α), a product of mononuclear phagocyte activation, patients with hemoglobin E/ß-thalassemia (E/ß-Thal) were studied. Whole blood of 20 nonsplenectomized, 20 splenectomized E/ß-Thal patients, and 20 healthy subjects was assayed for PS-RBCs; for monocytes, activated monocytes, and monocyte response to lipopolysaccharide stimulation; and serum was assayed for TNF-α. Asplenic E/ß-Thal patients had significantly increased (P < 0.05) amounts of PS-RBCs, monocytes, activated monocytes, and levels of serum TNF-α. The amount of PS-RBCs correlated with levels of serum TNF-α, but the amount of activated monocytes did not correlate with either the amount of PS-RBCs or levels of serum TNF-α. Monocyte response to lipopolysaccharide stimulation in asplenic patients was not as efficient as in the other patients or in normals (77 vs. 404, and 304 folds increment, respectively). The results suggest that splenectomy in E/ß-Thal patients led to an increased amount of PSRBCs and activation in the mononuclear phagocytic system.

Molecular screening of the Hbs Constant Spring (codon 142, TAA>CAA, α2) and Paksé (codon 142, TAA>TAT, α2) mutations in Thailand.

Hb Constant Spring [Hb CS, α142(H19)Term] and Hb Paksé [α142(H19)Term] occur from the mutation in the termination codon of the α2-globin gene, TAA>CAA (→Gln) and TAA>TAT (→Tyr), respectively. They are the most common nondeletional α-thalassemia (α-thal) variants causing Hb H disease in Southeast Asia. In this study, 587 cord blood samples were screened for the Hb CS and Hb Paksé mutations by a dot-blot hybridization technique using oligonucleotide probes specific for each mutation. The results showed that the prevalence of Hb CS and Hb Paksé in Central Thailand are 5.80 and 0.51%, respectively, which is in concordance with the results from previous studies.

Laboratory predictors of dengue shock syndrome during the febrile stage.

The clinical manifestations of dengue hemorrhagic fever (DHF) consist of three successive stages: febrile, toxic and convalescent. The toxic stage is the critical period, which may manifestas circulatory disturbance or even profound shock in some patients. We attempted to determine predictors for the risk of dengue shock syndrome (DSS) during the febrile stage. One hundred one children with acute febrile illness were enrolled in the study, with a mean age of 11 years old. The diagnosis included dengue fever (DF) 21 cases, DHF grade I 30 cases, DHF grade II 33 cases, DHF grades III and IV 10 cases; children with other febrile illnesses (OFI) 7 cases were used as controls. Complete blood counts, coagulation tests, von Willebrand factor antigens (VWF:Ag) and ristocetin cofactor activity (VWF:Rcof) were determined daily during hospitalization and 2-4 weeks after discharge from the hospital. The results revealed any one of the following abnormal laboratory findings during the febrile stage served as a predictor for risk of DSS: increase in hematocrit > 25%, a platelet count < 40,000/microl, an activated partial thromboplastin time >44 seconds, a prothrombin time >14 seconds, a thrombin time >16 seconds or a VWF:Ag or VWF:Rcof > 210%. The relative risk ranged from 4.8 to 10.9. Simple laboratory investigations with complete blood count, coagulation test or the more sophisticated von Willebrand factor, are helpful in predicting the risk for DSS during the febrile stage.

Hb Tak and Hb Q-Thailand in Thai patients are S-window hemoglobin variants revealed by high performance liquid chromatography.

The S-window hemoglobin (Hb) variants revealed by high performance liquid chromatography (HPLC) were studied in 12 Thai individuals. The variants were identified, using DNA sequencing and multiplex amplification refractory mutation system-polymerase chain reaction (ARMS-PCR), to be six cases of Hb Tak [beta147 (+AC)], and six cases of Hb Q-Thailand [alpha74(EF3)Asp-->His], respectively. By using the Capillarys 2-capillary zone electrophoresis (CE), Hb Tak and Hb Q-Thailand co-migrated with Hb F in zone 7. This might pose a problem as the high Hb F conditions suggest a differential diagnosis. The S-window Hb variants are mostly Hb Tak and Hb Q-Thailand in the Thai population rather than Hb S [beta6(A3)Glu-->Val]. The definite identification of Hb variants detected by HPLC or capillary electrophoresis (CE) requires DNA analysis.