Mixing Studies | Coagulation - MedSchool
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Coagulation
 
 
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Mixing studies are used to determine the cause of prolonged PT/INR and/or APTT. When performing mixing studies, the patient's plasma is mixed 50:50 with control plasma, and then the PT/INR or APTT is measured.
 

Mixing Studies

 
 
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Overview

  • Mixing studies are used to determine the cause of prolonged PT/INR and/or APTT.
  • When performing mixing studies, the patient's plasma is mixed 50:50 with control plasma, and then the PT/INR or APTT is measured.
    • Interpretation

    • If the APTT or PT/INR is initially elevated but becomes normal when control plasma is added, this suggests that there is factor deficiency as the cause of coagulopathy.
    • If the APTT or PT/INR remains elevated despite addition of control plasma, this suggests that there is an inhibitor present in the sample.

Correction of PT/INR with Mixing

  • If the PT/INR is initially elevated but becomes normal when control plasma is added, this suggests that there is factor deficiency as the cause of coagulopathy.
  • This occurs commonly in the setting of warfarin or vitamin K deficiency, however may occur in the context of deficiencies affecting multiple pathways.
    • Causes of PT/INR Correction with Mixing

    • Warfarin
    • Vitamin K deficiency
    • Congenital factor deficiency
    • Disseminated intravascular intracoagulation
    • Liver failure

Non-Correction of PT/INR with Mixing

  • If the PT/INR remains elevated despite addition of control plasma, this suggests that there is an inhibitor present in the sample.
    • Causes of PT/INR Non-Correction with Mixing

    • Factor IIa inhibitors (e.g. dabigatran)
    • Excess heparin in the tube

Correction of APPT with Mixing

  • If the APTT is initially elevated but becomes normal when control plasma is added, this suggests that there is factor deficiency as the cause of coagulopathy.
    • Causes of APTT Correction with Mixing

    • Congenital factor deficiency
    • Von Willebrand disease
    • Disseminated intravascular coagulation
    • Supratherapeutic warfarin

Non-Correction of APTT with Mixing

  • If the APTT remains elevated despite addition of control plasma, this suggests that there is an inhibitor present.
  • This occurs commonly in the context of heparin, though may also occur with antiphospholipid syndrome.
    • Causes of APTT Non-Correction with Mixing

    • Heparin
    • Factor IIa inhibitors (e.g. dabigatran)
    • Lupus anticoagulant
    • Specific factor inhibitors
Last updated on April 20th, 2020
 
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 Barras M. Anti-Xa assays. Australian Prescriber. 2013 Jun 1;36(3). Besser MW, MacDonald SG. Acquired hypofibrinogenemia: current perspectives. Journal of blood medicine. 2016;7:217. Chitolie A, Mackie IJ, Grant D, Hamilton JL, Machin SM. Inaccuracy of the'derived'fibrinogen measurement. Blood coagulation & fibrinolysis. 1994 Dec 1;5(6):955-7.
Chng WJ, Sum C, Kuperan P. Causes of isolated prolonged activated partial thromboplastin time in an acute care general hospital. Singapore medical journal. 2005 Sep;46(9):450.
 Chopra N, Doddamreddy P, Grewal H, Kumar PC. An elevated D-dimer value: a burden on our patients and hospitals. International journal of general medicine. 2012;5:87. Eisenberg JM, Clarke JR, Sussman SA. Prothrombin and Partial Thromboplastin Times as Preoperative Screening Tests. Arch Surg. 1982; 117(1): 48-51. Eisenberg JM, Clarke JR, Sussman SA. Prothrombin and Partial Thromboplastin Times as Preoperative Screening Tests. Arch Surg. 1982; 117(1): 48-51.  Giannitsis E, Mair J, Christersson C, Siegbahn A, Huber K, Jaffe AS, Peacock WF, Plebani M, Thygesen K, Möckel M, Mueller C. How to use D-dimer in acute cardiovascular care. European Heart Journal: Acute Cardiovascular Care. 2017 Feb;6(1):69-80. Kamal AH, Tefferi A, Pruthi RK. How to interpret and pursue an abnormal prothrombin time, activated partial thromboplastin time, and bleeding time in adults. InMayo Clinic Proceedings 2007 Jul 31 (Vol. 82, No. 7, pp. 864-873). Elsevier. Katayev A, Balciza C, Seccombe DW. Establishing Reference Intervals for Clinical Laboratory Test Results: Is There a Better Way?. Am J Clin Pathol. 2010; 133(2): 179. Levi M, Opal SM. Coagulation abnormalities in critically ill patients. Critical care. 2006 Jul 19;10(4):222. Lowe GD, Rumley A, Mackie IJ. Plasma fibrinogen. Ann Clin Biochem. 2004; 41: 430. Mani H. Interpretation of coagulation test results under direct oral anticoagulants. International journal of laboratory hematology. 2014 Jun 1;36(3):261-8. Oliver Speer O, Schmugge M, Metzger C, Albisetti M. Reference Ranges of Coagulation Tests. Methods in molecular biology. 2013; 992: 85. Palta S, Saroa R, Palta A. Overview of the coagulation system. Indian journal of anaesthesia. 2014 Sep;58(5):515. Peyvandi F, Garagiola I, Baronciani L. Role of von Willebrand factor in the haemostasis. Blood Transfusion. 2011 May;9(Suppl 2):s3. Wakai A, Gleeson A, Winter D. Role of fibrin D-dimer testing in emergency medicine. Emergency Medicine Journal. 2003 Jul 1;20(4):319-25.
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