Mixing Study Limits

Mixing Study Limits
May 22, 2021 9:01am

From a participant: Can you please help me to understand how to make a cut off value for a correction study so that above this value is corrected and below is not?
Please provide an example. Thank you.


Hello, and thank you for your question. Please click this link to our educational module, "Improving Acute Care Using Coagulation Mixing Studies." You will find the answer in slides 22–24 and several examples throughout the module. My personal preference is to establish the decision point at 10% above the mean of the PTT reference interval, however many choose the Rosner index and some choose a fixed PTT value such as 5 seconds over the upper limit of the reference interval. I hope this is helpful.

1 Comment

From a participant: Can you please help me to understand how to make a cut off value for a correction study so that above this value is corrected and below is not?
Please provide an example. Thank you.


Hello, and thank you for your question. Please click this link to our educational module, "Improving Acute Care Using Coagulation Mixing Studies." You will find the answer in slides 22–24 and several examples throughout the module. My personal preference is to establish the decision point at 10% above the mean of the PTT reference interval, however many choose the Rosner index and some choose a fixed PTT value such as 5 seconds over the upper limit of the reference interval. I hope this is helpful.

By Dr Emmanuel Favaloro
Jun 18, 2021 10:34pm
I would also recommend these publications, which provide several options and examples: Kershaw G. Performance and interpretation of mixing tests in coagulation. Methods Mol Biol. 2017;1646:85–90. doi: 10.1007/978-1-4939-7196-1_6. PubMed PMID: 28804820, and Kershaw G, Orellana D. Mixing tests: diagnostic aides in the investigation of prolonged prothrombin times and activated partial thromboplastin times. Semin Thromb Hemost. 2013;39:283–90. doi: 10.1055/s-0033-1336832. Epub 2013 Mar 2. PubMed PMID: 23457048.
Important to understand that no method is foolproof, and there may be an overlap of ~10% between cases with inhibitors vs factor deficiencies.

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