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plasma mixing studies
A set of tests in which the patient's plasma is mixed with plasma from a healthy individual or with pooled plasma.
Indications:
- coagulation factor deficiency
- coagulation factor inhibitor
Principle:
- addition of normal plasma to the patient's plasma will correct a deficiency in a coagulation factor, whereas will have less if any effect on a coagulation factor inhibitor
- the PT may correct initially after mixing, but not after 1 hour of incubation
* excess phospholipid is added to the patient's plasma & the aPTT corrects is consistent with antiphospholipid syndrome [3]
Interpretation:
- mixing studies correct PT & aPTT for
a) hepatic cirrhosis
b) vitamin K deficiency
c) disseminated intravascular coagulation (DIC)
d) von Willebrand disease including acquired von Willebrand disease [2]
e) hemophilia
- aPTT does not correct for coagulation factor inhibitor
- acquired hemophilia A (factor VIII inhibitor) [2]
- correction of aPTT without correction of PT (after incubation) suggests inhibitor of coagulation factor VIIA
- 'correction' is an ambiguous term
- complete correction of aPTT would imply aPTT < 35 seconds
- a correction of aPTT from 85 seconds to 48 seconds or 90 seconds to 45 seconds is only a partial correction & is consistent with a coagulation factor inhibitor [1]
General
clinical coagulation test
References
- Medical Knowledge Self Assessment Program (MKSAP) 16, 17
American College of Physicians, Philadelphia 2012, 2015
- Geriatric Review Syllabus, 11th edition (GRS11)
Harper GM, Lyons WL, Potter JF (eds)
American Geriatrics Society, 2022
- NEJM Knowledge+ Hematology