Prolonged partial thromboplastin time: To mix or not to mix – is that the question?

Sean G. Yates, Eric Fitts, Nicole De Simone, Ravi Sarode

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Routine mixing studies are frequently used to evaluate patients presenting with prolonged partial thromboplastin times (PTT) and/or prothrombin times (PT). Unfortunately, mixing studies have a number of inherent limitations including lack of standardization in terms of what defines normal pooled plasma (NPP), the processing of a patient's plasma for platelet removal (platelet poor plasma versus platelet-free plasma), performance of appropriate controls, conducting an incubation step to evaluate for a time and temperature dependent inhibitor, and finally interpretation of test results. Moreover, misinterpretation of study results can lead to a delayed or incorrect diagnosis or worse, inappropriate treatment. Within this manuscript, we present four cases illustrating the shortcomings associated with inappropriate utilization and interpretation of routine mixing studies; and present practical steps for managing abnormal PT or PTT results.

Original languageEnglish (US)
Pages (from-to)39-42
Number of pages4
JournalTransfusion and Apheresis Science
Issue number1
StatePublished - Feb 2019


  • Circulating coagulation inhibitor
  • Lupus anticoagulant
  • Mixing study
  • Partial thromboplastin time
  • Prothrombin time

ASJC Scopus subject areas

  • Hematology


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