[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Arg531His (R531H) mutation was identified from unrelated two Japanese patients with cross reacting material positive (CRM+) mild hemophilia A. Although these patients have the same genetic defect and mild clinical phenotype, FVIII activity differed considerably, between the two. In Patient 1, FVIII activity, measured with 14 different APTT reagents, ranged widely, from 25.2% to 48.1%. There was a negative correlation between reagent pH and R531H measurement. Although the FVIII activity in Patient 2 also showed a discrepancy, the difference was considerably lessened by use of an imidazole buffer for sample dilution solution. This finding suggests that the use of imidazole buffer as a sample diluent is an effective means for reducing the wide range of assay results. As for the results of the present study, FVIII levels associated with the R531H mutation differed with the patients and were greatly influenced by measurement method. It is necessary to establish a standard method that can detect and characterize the mild hemophilia phenotype caused by a particular mutation, such as Arg531His.

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Recently, a thrombin generation test (TGT) has been reported as a novel method that might be able to reflect the status of both hemorrhage and thrombotic diseases in vivo. A central venous catheter (CVC) line is frequently applied among children and heparin is usually used as anticoagulant not to occlude the line. Therefore, blood sample collected from CVC-line contains heparin to some extent, thus disturbing the assessment of coagulation activity in vivo. For the application of blood obtained via CVC-line, the effect of heparin on coagulation and the heparin-neutralizing effects of both protamine sulfate and heparinase were examined, with special reference to TGT. As in the results, TGT was more sensitively affected by heparin than APTT and PT.
Protamine sulfate has completely neutralized heparin only at an optimal concentration, however, it has suppressed thrombin generation in excess dosage in a dose-dependent manner. Heparinase, on the other hand, has completely neutralized heparin without interfering thrombin generation not only at an optimal concentration, but also in excess dosage. In view of these findings, it was concluded that the TGT determination using heparinase is available when evaluating the coagulation activity of heparin-containing blood.

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