Evaluation of prolonged surface activated coagulation time

• Main Author: Jesting, Amalie
• Format: Others
• Language: Swedish
• Published: Malmö universitet, Fakulteten för hälsa och samhälle (HS) 2019
• Subjects: Blood test; Engineering and Technology; Teknik och teknologier
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-27144

Background: Blood coagulation is an essential defense mechanism to prevent bleeding. Disorders in the coagulation system can be severe and blood tests measuring the blood’s ability to coagulate are important. Activated partial thromboplastin time (APTT) is a blood test that measures blood coagulation time. An abnormal prolonged APTT can both be associated with a bleeding tendency or a risk of thrombosis. Additional blood tests are needed to discover the cause of a prolonged APTT. One potential test is the APTT mixing study, which can separate samples with and without inhibitors. The aim of this project is to investigate how the cause of a prolonged APTT is evaluated today and to examine if it is possible to indicate the cause of a prolonged APTT using the APTT mixing study performed on routine samples. The goal is to be able to indicate the cause of a prolonged APTT immediately when is it first discovered. This will save time and help guide the physicians in their work with the patient. Methods: Retrospective data is used to examine how the cause of a prolonged APTT is evaluated today. Samples with known cause of prolonged APTT are used to establish a cut-off value for the APTT mixing study to indicate the cause of a prolonged APTT. The cut-off values are then tested using routine APTT samples. Pre-analytical variables relevant to APTT are also investigated. Results: Today, specialized departments request most special coagulation blood tests. The APTT mixing study can separate samples with and without inhibitors with 90% specificity and sensitivity using index of circulating anticoagulants cut-off value of 16.0. In regard to pre-analytical variables, the centrifugation force affects the plasma platelet count but not APTT and sample storage has an affect on APTT. Conclusion: The APTT mixing study can be implemented as an additional test to indicate the cause of a prolonged APTT on routine samples.