Al-Sallami Hesham S, Medlicott Natalie J
School of Pharmacy, University of Otago, Dunedin, New Zealand.
J Pharm Pharmacol. 2015 Feb;67(2):209-14. doi: 10.1111/jphp.12333. Epub 2014 Dec 31.
Enoxaparin is a low-molecular weight heparin (LMWH) widely used for the treatment of thrombosis and measured through a chromogenic assay (anti-Xa). The aim of this project was to investigate the impact of patient and sampling sources of variation on an anti-Xa assay for enoxaparin.
COATEST was used in accordance with manufacturer's instructions. A standard curve of LMWH concentration (0.1-1.0 IU/ml) was prepared. The shelf-life and freeze-thaw stability of Xa over a 6-month period were investigated. The effects of blood sample haemolysis and plasma antithrombin-III (AT) concentration were examined.
The standard curve performed well with high accuracy (average bias of 8.1%) and precision (average CV of 2.8%). The shelf-life of Xa once reconstituted could be extended from 1 month to 4 months if aliquots were frozen at -20°C. Some loss of anti-Xa activity was observed on freeze-thawing (bias up to 25%). Haemolysis of 2.5% was found to interfere with the assay. AT level as low as 50% did not affect assay accuracy.
Xa standards when frozen immediately after reconstitution could be used for the following 4 months. Haemolysis interferes with the assay, but a 50% reduction in AT does not significantly affect the assay result.
依诺肝素是一种广泛用于治疗血栓形成的低分子肝素（LMWH），通过显色测定法（抗Xa）进行检测。本项目旨在研究患者和样本来源的变异对依诺肝素抗Xa测定的影响。
按照制造商的说明使用COATEST。制备了低分子肝素浓度（0.1 - 1.0 IU/ml）的标准曲线。研究了Xa在6个月期间的保质期和冻融稳定性。检查了血样溶血和血浆抗凝血酶III（AT）浓度的影响。
标准曲线表现良好，具有高精度（平均偏差8.1%）和精密度（平均CV为2.8%）。如果将分装物在-20°C冷冻，Xa复溶后的保质期可从1个月延长至4个月。冻融时观察到抗Xa活性有一些损失（偏差高达25%）。发现2.5%的溶血会干扰测定。低至50%的AT水平不会影响测定准确性。
Xa标准品复溶后立即冷冻可在接下来的4个月内使用。溶血会干扰测定，但AT降低50%不会显著影响测定结果。
