Ip B K, Thomson A R, Moriarty H T
Haematology, Concord Repatriation General Hospital, Concord, NSW, Australia.
Pathology. 2001 Aug;33(3):347-52.
Low-molecular weight heparin (LMWH) is the product of enzymatic or chemical degradation of unfractionated heparin (UFH). It has been found to have better bio-availibility, more predictable dose response and can be used as an alternative to UFH for prophylaxis and treatment of thrombotic disorders. It is claimed that no laboratory monitoring is necessary for LMWH therapy; however, for the aged, renal impaired, obese or grossly underweight, monitoring of dose effect with anti-Xa assay is recommended. The activated partial thromboplastin time (APTT), which is the test of choice for UFH monitoring, is believed to be insensitive to the effect of LMWH. The sensitivity of the APTT to heparin lies in the APTT reagent used. In this study, eight different APTT reagents were used to compare the APTT with anti-Xa activity in ex vivo plasma from patients who were on enoxaparin (LMWH, Clexane) therapy. It was found that, as with UFH, APTT reagents show variable sensitivity to LMWH. The APTTs from all eight reagents were found to have a linear relationship to anti-Xa activity. The APTT results using three of the reagents gave an indication of the use of LMWH therapy. It was also found that patients who were lupus anticoagulant (LA)-positive had much more prolonged APTTs when on LMWH therapy; however, a linear correlation between APTT and anti-Xa was not present in these patients.
低分子量肝素（LMWH）是普通肝素（UFH）经酶解或化学降解后的产物。已发现它具有更好的生物利用度、更可预测的剂量反应，并且可作为UFH的替代品用于血栓性疾病的预防和治疗。据称，LMWH治疗无需实验室监测；然而，对于老年人、肾功能受损者、肥胖者或体重明显过轻者，建议用抗Xa测定法监测剂量效应。活化部分凝血活酶时间（APTT）是监测UFH的首选检测方法，但据信它对LMWH的效应不敏感。APTT对肝素的敏感性取决于所用的APTT试剂。在本研究中，使用了八种不同的APTT试剂，以比较接受依诺肝素（LMWH，克赛）治疗患者的离体血浆中APTT与抗Xa活性。结果发现，与UFH一样，APTT试剂对LMWH的敏感性各不相同。发现所有八种试剂的APTT与抗Xa活性均呈线性关系。使用其中三种试剂得到的APTT结果可用于指示LMWH治疗的使用情况。还发现，狼疮抗凝物（LA）阳性的患者在接受LMWH治疗时APTT延长得多；然而，这些患者的APTT与抗Xa之间不存在线性相关性。
