Mutations at the activated protein C cleavage sites Arg336 and Arg562 of factor VIII in Thai patients with venous thrombosis.

Venous thrombosis is a multicausal disease, more than one genetic risk factor may cooperate to effect thrombotic risk. Factor V Leiden is found to be an important hereditary risk factor for venous thromboembolism. Analogous to factor V Leiden, a point mutation at amino acid positions Arg336 and Arg562 in factor VIII may predispose patients to thrombosis. Eighty-one Thai patients with venous thrombosis and 100 Thai healthy volunteers have been studied. Neither heterozygous nor homozygous mutations were detected both thrombosis patients or normal volunteers. However, further studies with larger samples of venous thrombosis patients are recommended.

Detection of factor V Leiden in Thai patients with venous thrombosis.

The molecular defect underlying activated protein C resistance (APC-R) is caused by a G to A point mutation in the codon for arginine 506 in the factor V gene (factor V Leiden) which is a major risk factor for venous thrombosis, especially in Caucasian populations. This study is an analysis of the Thai population to determine the prevalence of the factor V Leiden mutation. Twenty-seven patients with apparent venous thrombosis were divided into two groups according to APC-R test. Thirteen patients were diagnosed as positive for n-APC-SR, ratio < 0.8 and fourteen patients were diagnosed as negative for n-APC-SR, ratio > 0.8. Two of thirteen APC-R positive patients and one of fourteen APC-R negative patients were found to have the heterozygous allele for the factor V Leiden mutation but the homozygous allele was not detected in these groups of patients. Neither the heterozygous nor homozygous Leiden mutation was detected in 200 healthy volunteer blood donors. In conclusion, our findings indicate that factor V Leiden mutation is related to venous thrombosis in Thai people. Moreover, a further study of other mutations at the activated protein C cleavage sites of factor V and factor VIII is recommended.

Comparison of the RPHA and EIA techniques for the detection of HBs antigen among pregnant Thai women.

Five hundred serum samples obtained from pregnant women attending an antenatal clinic in Bangkok were tested for HBsAg by reverse passive hemagglutination assay (RPHA) and enzyme immunoassay (EIA). It was found that 21 (4.2%) and 28 (5.6%) of the sera were positive by RPHA and EIA, respectively. The sensitivity and specificity of the RPHA were 75% and 100%, respectively, when using EIA as the standard method. The RPHA positive predictive value was 100% and the negative predictive value was 98.5%. Accuracy was 98.6%. This study showed that the RPHA was simple and required inexpensive equipment, making it suitable for mass screening. However, the possibility of false negative readings due to low levels of HBsAg should be kept in mind, especially in the blood transfusion practice.

Control cells for both electrical impedance and light scattering automated hematological analyzers: preparation from normal and thalassemic blood samples.

The study on quality control of automated blood cell analyzers, Technicon H*1 and Coulter MAXM by using three separately self-prepared control cells was extensively investigated. The three parts of control cells are pseudo-leukocyte and fixed platelets, which are fixed by glutaraldehyde, and control red cells from normal and thalassemic patients preserved and anticoagulated in CPD or CPDA-1. The Technicon H*1 system was based on the principle of light scattering but the Coulter MAXM was based on the principle of electrical impedance for cell counting and measurement. The self-prepared control cells can be satisfactorily utilized as control for each system with statistically significant difference (p < 0.05) for both systems. The expired dates for control cells are different in both systems and should be determined for each system specifically. The control red cells prepared from thalassemic patients were quite satisfactorily useful as an abnormal control for both systems during this study.

High transfusion in children with beta-thalassemia/Hb E: clinical and laboratory assessment of 18 cases.

Between 1990-1992, 18 patients with beta-thalassemia/Hb E age between 2-13 years (mean 7.4 +/- 3 years) were examined. Three patients were splenectomized and the rest were nonsplenectomized. They were divided into 3 groups. Group A:5 nonsplenectomized and 3 splenectomized patients had high transfusion rates with subcutaneous desferrioxamine injections. Five patients in group B received only high transfusion whereas in 5 patients in group C the levels pretransfusion Hb were maintained between 6-7 g/dl. The mean blood consumption in the nonsplenectomized groups were 220 +/- 25.3, 221 +/- 59 and 175.4 +/- 45.4 ml/kg/year in groups A, B and C, respectively. In group A, the mean blood requirement was 40% higher in the nonsplenectomized group. In the high transfusion regimen the spleen size did not increase and serum aspartate aminotransferase showed a striking fall in the majority of cases. The absolute increases in serum ferritin were 843.2 +/- 395, 861 +/- 252 and 1,262 +/- 440 ng/ml in groups A, B and C, respectively. These data demonstrated that high transfusion with desferrioxamine injection could improve the clinical well being of the patients.