Plasma sample dilution improves the correlation: between reagents for PT methods
2007 (English)In: XXIst ISTH Congress, 2007Conference paper (Refereed)
Introduction: The Quick (plain thromboplastins) and Owren (combined thromboplastins) PT methods are used worldwide for the monitoring of anticoagulation therapy with vitamin K antagonists. Although both methods measure the activity of vitamin K dependent coagulation factors, the Quick PT-result in addition is dependent on the activity of factor V and of fibrinogen. The Quick PT-methods are also associated with larger inter-laboratory variations than Owren PT-methods. We have investigated whether the dilution of the sample, the source of depleted plasma or the source of thromboplastin have an impact on the correlation between the different PT-reagents.
Methods: Patient and quality control samples were analysed undiluted and prediluted 2x, 7x, 10x, and 12x in Owren's buffer. One part of sample was then mixed with two parts of reagent and calcium. Bovine vs. human depleted plasmas and rabbit brain vs. human placenta thromboplastins were compared in combinations. The assays were run on an ACL Top from Instrumentation Laboratory (Italy).
Results: Our results show that the dilution of the sample is important for the correlation between different PT-reagents. We found the best correlation (r = 0.95) when the sample was 7-fold prediluted (1 part + 6 parts). The lowest correlation was found when the sample was undiluted (r = 0.67). The source of thromboplastin had a small, if any, impact on the PT-results provided the sample was prediluted.The source of depleted plasma had no significance for the relationship between the PT-reagents. The depleted plasma is necessary to in order enable clotting of prediluted plasma.
Conclusions: We conclude that the Owren style sample dilution is to prefer for the harmonization of PT-results and to overcome the large inter-laboratory variations that are associated with Quick PT-methods.
Place, publisher, year, edition, pages
National CategoryMedical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-14490OAI: oai:DiVA.org:liu-14490DiVA: diva2:23585
This paper is published in volume 5, supplement 1 of Journal of Thrombosis and Haemostasis (2007).2007-05-212007-05-212009-12-18